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CHU VAN BIEN
GIAO VIEN CHNG TRNH BO TR KIEN THC VAT L 12
KENH VTV2 AI TRUYEN HNH VIET NAM
PHIEN BAN MI NHAT
Phan III. SONG C, SONG IEN T, IEN T
SONG ANH SANG, LNG T ANH SANG,
HAT NHAN
NH XUT BN I HC S PHM TP H CH MINH
MUC LUC
GIAI NHANH SONG C, DAO ONG VA SONG IEN T, SONG
ANH SANG, LNG T ANH SANG, HAT NHAN NGUYEN T
TRONG E CUA BO GIAO DUC ........................................................... 3
Chu e 1. HIEN TNG SONG C HOC ........................................ 48
Chu e 2. SONG DNG .................................................................... 80
Chu e 3. GIAO THOA SONG C HOC ......................................... 104
Chu e 4. SONG AM ....................................................................... 169
Chu e 5. DAO ONG IEN T .................................................... 185
Chu e 6. DAO ONG IEN T ..................................................... 230
Chu e 7. HIEN TNG TAN SAC ANH SANG ........................... 252
Chu e 8. HIEN TNG GIAO THOA ANH SANG ...................... 267
Chu e 9. QUANG PHO. CAC TIA ................................................. 327
Chu e 10. HIEN TNG QUANG IEN ........................................ 334
Chu e 11. THUYET BO. QUANG PHO HIRO.
S PHAT QUANG TIA X .............................................. 356
Chu e 12. TNH CHAT VA CAU TAO HAT NHAN ...................... 375
Chu e 13. PHAN NG HAT NHAN ................................................ 380
Chu e 14. PHONG XA. PHAN HACH. NHIET HACH ................... 399
CAU HOI LY THUYET ....................................................................... 433
Cty TNHH MTV DVVH Khang Viet
3
GII NHANH SNG C, DAO NG V SNG IN T, SNG NH SNG, LNG T NH SNG, HT NHN
NGUYN T TRONG THI CA B GIO DC 1. NM 2010
Sng c hc
Cu 1: (H-2010): iu kin hai song c khi gp nhau, giao thoa c vi nhau la
hai song phai xut phat t hai ngun dao ng
A. cung bin va co hiu s pha khng i theo thi gian.
B. cung tn s, cung phng.
C. co cung pha ban u va cung bin .
D. cung tn s, cung phng va co hiu s pha khng i theo thi gian.
Hng dn
hai song c khi gp nhau , giao thoa c vi nhau la hai song phai xut phat t
hai ngun dao ng cung tn s, cung phng va co hiu s pha khng i theo thi
gian Chn D.
Cu 2: (H-2010) Tai mt im trn mt cht long co mt ngun dao ng vi tn s
120 Hz, tao ra song n inh trn mt cht long . Xet 5 gn li lin tip trn mt phng
truyn song, v mt phia so vi ngun, gn th nht cach gn th nm 0,5 m. Tc
truyn song la
A. 12 m/s. B. 15 m/s. C. 30 m/s . D. 25 m/s.
Hng dn
1 1
5 1 0,5 .120 15 /8 8
x m v f m s Chn B.
Cu 3: (H-2010) Mt si dy AB dai 100 cm cng ngang, u B c inh, u A gn
vi mt nhnh ca m thoa dao ng iu ha vi tn s 40 Hz. Trn dy AB c mt
sng dng n inh, A c coi l nt sng. Tc truyn sng trn dy l 20 m/s. K
ca A v B, trn dy c
A. 3 nt v 2 bng. B. 7 nt v 6 bng. C. 9 nt v 8 bng. D. 5 nt v 4 bng.
Hng dn
20
0 5 5040
v, m cm
f . V hai u u l nt nn s nt nhiu hn s
bng l 1: 4
0 5
1 5
ABsb
,
sn sb
Chn D.
Cu 4: (H-2010) mt thong ca mt cht long c hai ngun sng kt hp A v B
cach nhau 20 cm, dao ng theo phng thng ng vi phng trnh uA = 2cos40t
v uB = 2cos(40t + ) (uA v uB tnh bng mm, t tnh bng s). Bit tc truyn sng
Tuyet pham cong pha Vat l GNTC tren kenh VTV2 Chu Van Bien
4
trn mt cht long l 30 cm/s. Xt hnh vung AMNB thuc mt thong cht long. S
im dao ng vi bin cc ai trn oan BM l
A. 19. B. 18. C. 20. D. 17.
Hng dn
Cch 1:
2 28,28
21,5
NA MB AB cm
vT v cm
2 1
2 1
20 28 28 05 02
2 1 5 2
20 0 013 83
2 1 5 2
M
B
MA MB ,k ,
,
BA BBk ,
,
5 02 13 83 5 13, k , k ,..., S cc i :c 19 cc i
Chn A.
Cch 2:
Hai ngun kt hp ngc pha:
1 2
1 2 0,5
d d
d d k
iu kin cc tiu : - = m
iu kin cc i : - =
Cc ai thuc BM:
1 2
1 2
- 0,5 0,5 1,5
-
d d k k
MA MB d d BA BB
8,3 0,5 1,5 20k
6,03 12,8 6, 5, 4,...,12k k c 19 gi tr ca k
Cu 5: (H-2010) Ba im O, A, B cng nm trn mt na ng thng xut pht t
O. Tai O t mt ngun im phat song m ng hng ra khng gian, mi trng
khng hp th m. Mc cng m tai A l 60 dB, tai B l 20 dB. Mc cng m
tai trung im M ca oan AB l
A. 26 dB. B. 17 dB. C. 34 dB. D. 40 dB.
Hng dn
V M la trung im ca AB nn 2rM = rA + rB (1)
V 0 5
02
0
10 104 4 4
L , LOWP PI I . r .r I I
, r t l vi 10-0,5L
. Do ,
trong (1) ta thay r bi 10-0,5L
ta c 0 5 0 5 0 5
2 10 10 10M A B, L , L , L
.
0 5 0 53 12 10 10 10 10 0 0505 2 6M M, L , L M. , L , B Chn A.
Dao ng v sng in t
Cu 6: (H-2010) Mt mach dao ng li tng gm cun cam thun co t cam 4
H v mt t in co in dung bin i t 10 pF n 640 pF. Ly 2
= 10. Chu k dao
ng ring ca mach ny c gi tri l
Cty TNHH MTV DVVH Khang Viet
5
A. t 2.10-8
s n 3.10-7
s. B. t 4.10-8
s n 3,2.10-7
s.
C. t 2.10-8
s n 3,6.10-7
s. D. t 4.10-8
s n 2,4.10-7
s.
Hng dn
6 12 8
1 1
6 12 7
2 2
2 2 4 10 10 10 4 102
2 2 4 10 640 10 3 2 10
T LC . . . . sT LC
T LC . . . , . s
Chn B.
Cu 7: (H-2010) Mt mach dao ng li tng gm cun cam thun co t cam L
khng i va tu in co in dung C thay i c . iu chinh in dung cua tu in
n gia tri C 1 th tn s dao ng ring ca mach la f 1. tn s dao ng ring cua
mach la f1 5 th phai iu chnh in dung ca t in n gia tri
A. C1/5. B. 0,2C1 5 . C. 5C1. D. C1 5 .
Hng dn
T 1
2f
LC ta thy f t l vi
1
C
2 1 1 12
1 2 2
55
f C C CC
f C C
Chn A.
Cu 8: (H-2010) Mt mach dao ng in t li tng ang co dao ng in t t
do. Tai thi im t = 0, in tch trn mt ban t in cc ai. Sau khoang thi gian ngn
nht t th in tch trn ban t ny bng mt na gi tri cc ai. Chu k dao ng ring
ca mach dao ng ny l
A. 4t. B. 6t. C. 3t. D. 12t.
Hng dn
Thi gian ngn nht t q = Q0 n q = Q0/2 l t = T/6 T = 6 t Chn B.
Cu 9: (H-2010) Xt hai mach dao ng in t li tng. Chu k dao ng ring ca
mach th nht l T1, ca mach th hai l T2 = 2T1. Ban u in tch trn mi ban t
in co ln cc ai Q0. Sau o mi t in phong in qua cun cam ca mach. Khi
in tch trn mi ban t ca hai mach u co ln bng q (0 < q < Q0) th t s
ln cng dng in trong mach th nht va ln cng dng in trong mach
th hai l
A. 0,25. B. 0,5. C. 4. D. 2.
Hng dn
2 221 1 02 2 2 2 1 2
0 02 2 22 2 12 0
2i Q q Ti
Q q i Q qi TQ q
Chn D.
Cu 10: (H-2010) Trong thng tin lin lac bng song v tuyn , ngi ta s dung
cach bin iu bin , tc la lam cho bin cua song in t cao tn (gi la song
mang) bin thin theo thi gian vi tn s bng tn s cua dao ng m tn . Cho tn s
Tuyet pham cong pha Vat l GNTC tren kenh VTV2 Chu Van Bien
6
song mang la 800 kHz. Khi dao ng m tn co tn s 1000 Hz thc hin mt dao ng
toan phn th dao ng cao tn thc hin c s dao ng toan phn la
A. 1600. B. 625. C. 800. D. 1000.
Hng dn
p dng: 800.1000
8001 1000a a
n f nn
n f Chn C.
Cu 11: (H-2010) Mach dao ng dung chn song ca mt may thu v tuyn in
gm t in co in dung C 0 va cun cam thun co t cam L . May nay thu c
song in t co bc song 20 m. thu c song in t co bc song 60 m, phai
mc song song vi tu in C0 ca mach dao ng vi mt t in co in dung
A. C = 2C0. B. C = C0. C. C = 8C0. D. C = 4C0.
Hng dn
8
1 00
08
01 0
6 .10 203 8
6 .10 60
LC C CC C
CL C C
Chn C.
Cu 12: Mt mach dao ng li tng gm cun cam thun co t cam L va tu in
co in dung C ang co dao ng in t t do . thi im t = 0, hiu in th gia
hai ban tu co gia tri cc ai la U0. Phat biu nao sau y la sai?
A. Nng lng t trng cc ai trong cun cam la
2
0CU
2
B. Nng lng t trng cua mach thi im t LC2
la
2
0CU
4
C. Hiu in th gia hai ban tu in bng 0 ln th nht thi im t LC2
D. Cng dong in trong mach co gia tri cc ai la 0L
UC
Hng dn
20
0
0 0
2 4 2Lmax C max
t i
CUTt LC i I W W
Chn B.
Sng nh sng
Cu 13: (H2010) Tia t ngoai c dng
A. tm vt nt trn b mt san phm bng kim loai.
B. trong y t chp in, chiu in.
C. chp anh b mt Trai t t v tinh.
D. tm khuyt tt bn trong san phm bng kim loai.
Hng dn
Tia t ngoai c dng tm vt nt trn b mt san phm bng kim loai Chn A.
Cty TNHH MTV DVVH Khang Viet
7
Cu 14: (H2010) Quang ph vach pht xa
A. ca cc nguyn t khc nhau, cng mt nhit th nh nhau v sng t i ca
cc vach.
B. l mt h thng nhng vach sng (vach mu) ring l, ngn cach nhau bi nhng
khoang ti.
C. do cc cht rn, cht long hoc cht kh c p sut ln pht ra khi bi nung nng.
D. l mt dai c mu t o n tm ni lin nhau mt cch lin tc.
Hng dn
Quang ph vach pht xa l mt h thng nhng vach sng (vach mu) ring l, ngn
cch nhau bi nhng khoang ti Chn B.
Cu 15: (H2010) Khi ni v tia hng ngoai, pht biu nao di y la sai?
A. Tia hng ngoai cng co th bin iu c nh song in t cao tn.
B. Tia hng ngoai c kha nng gy ra mt s phan ng ha hc.
C. Tia hng ngoai c tn s ln hn tn s ca anh sang o.
D. Tc dng ni bt nht ca tia hng ngoai l tc dng nhit.
Hng dn
Tia hng ngoai c tn s be hn tn s ca anh sang o Chn C.
Cu 16: (H-2010) Trong th nghim Y-ng v giao thoa anh sang, hai khe c chiu
bng anh sang n sc co bc sng 0,6 m. Khoang cch gia hai khe l 1 mm,
khoang cch t mt phng cha hai khe n mn quan st l 2,5 m, b rng min giao
thoa l 1,25 cm. Tng s vn sng v vn ti c trong min giao thoa l
A. 19 vn. B. 17 vn. C. 15 vn. D. 21 vn.
Hng dn
12 52 1 2 1 2 4 17 1 9
1 5 2 2 1 5
1 8
s
t s
L ,N ,D
i , mm i . ,a
N N
17t sN N Chn B.
Cu 17: (H-2010) Trong thi nghim Y -ng v giao thoa anh sang , ngun sang phat
ng thi hai bc xa n sc , trong o bc xa mau o co bc song 720 nm va bc xa
mau lc co bc song (co gia tri trong khoang t 500 nm n 575 nm). Trn man
quan sat , gia hai vn sang gn nhau nht va cung mau vi vn sang trung tm co 8
vn sang mau luc. Gia tri ca la
A. 500 nm. B. 520 nm. C. 540 nm. D. 560 nm.
Hng dn
Cch 1: T kt qua
11 2 21 1 2 2
2 1 1 2
1
1
bk i bx k i k i
k i c c
vn sng
vn sng
Tuyet pham cong pha Vat l GNTC tren kenh VTV2 Chu Van Bien
8
Theo bi ra: c 1 = 8 nn c = 9. Suy ra: 500 5752 1 80b
b nmc
6,25 7,1875 7 560b b nm Chn D.
Cch 2: Vi tr vn sng trng gn vn trung tm nht: 1 2min 1min 2minD D
x k ka a
2min9 500 575
1min 2min 1min720 80k
k k k Hnh v suy ra:
1min 1min6,25 7,1875 7 560k k nm
Cu 18: (H-2010) Trong th nghim Y-ng v giao thoa anh sang, hai khe c chiu
bng nh sng trng co bc sng t 380 nm n 760 nm. Khoang cch gia hai khe l
0,8 mm, khoang cch t mt phng cha hai khe n mn quan st l 2 m. Trn mn,
tai vi tr cch vn trung tm 3 mm c vn sng ca cc bc xa vi bc sng
A. 0,48 m v 0,56 m. B. 0,40 m v 0,60 m.
C. 0,40 m v 0,64 m. D. 0,45 m v 0,60 m.
Hng dn
1 20 38 0 761 2
1 58 3 16 2 3
,, m ,
M kM
axD ,x k m , k , k ;
a kD k
0 6 0 4, m ; , m Chn B.
Cu 19: (H-2010) Trong thi nghim Y-ng v giao thoa anh sang, hai khe c chiu
bng anh sang n sc co bc song . Nu tai im M trn man quan sat co vn ti
th ba (tinh t vn sang trung tm) th hiu ng i cua anh sang t hai khe S1, S2 n
M co ln bng
A. 2,5. B. 3. C. 1,5. D. 2.
Hng dn
Vn ti th 3 th hiu ng i: d2 d1 = (3 0,5) = 2,5 Chn A.
Lng t nh sng
Cu 20: (H2010) Khi chiu chm tia t ngoai vo mt ng nghim ng dung dich
fluorexin th thy dung dich ny pht ra nh sng mu lc. o la hin tng
A. phan xa nh sng. B. quang - pht quang.
C. ha - pht quang. D. tn sc nh sng.
Hng dn
Khi chiu chm tia t ngoai vo mt ng nghim ng dung dich fluorexin th
thy dung dich ny pht ra nh sng mu lc. o la hin tng quang - pht quang
Chn B.
Cty TNHH MTV DVVH Khang Viet
9
Cu 21: (H2010) Mt kim loai c cng thot lectron l 7,2.10-19
J. Chiu ln lt
vo kim loai ny cc bc xa co bc sng 1 = 0,18 m, 2 = 0,21 m, 3 = 0,32 m v
4 = 0,35 m. Nhng bc xa c th gy ra hin tng quang in kim loai ny c
bc sng l
A. 1, 2 v 3. B. 1 v 2. C. 2, 3 v 4. D. 3 v 4.
Hng dn
Tnh gii han quang in: 60 0,276.10hc
mA
.
Ta thy: 1 < 2 < 0 < 3 < 4 nn ch c 1 v 2 l gy ra hin tng quang in
Chn B.
Cu 22: (H2010) Khi lectron qu ao dng th n th nng lng ca nguyn t
hir c tnh theo cng thc En =-13,6/n2 (eV) (n = 1, 2, 3,). Khi lectron trong
nguyn t hir chuyn t qu ao dng n = 3 sang qu ao dng n = 2 th nguyn t hir
pht ra phtn ng vi bc xa co bc sng bng
A. 0,4350 m. B. 0,4861 m. C. 0,6576 m. D. 0,4102 m.
Hng dn
Ta p dng: 63 23 2
0,6576.10hc hc
E E mE E
Chn C.
Cu 23: (H2010) Mt cht c kha nng phat ra anh sang phat quang vi tn s
f = 6.1014
Hz. Khi dung anh sang co bc song nao di y kch thch th cht ny
khng th pht quang?
A. 0,55 m. B. 0,45 m. C. 0,38 m. D. 0,40 m.
Hng dn
Bc sng pht quang 8
63.10 0,5.10 mf
< bc sng nh sng kch thch
Chn A.
Cu 24: (H2010) Theo tin ca Bo, khi lectron trong nguyn t hir chuyn t
qu ao L sang qu ao K th nguyn t pht ra phtn co bc sng 21, khi lectron
chuyn t qu ao M sang qu ao L th nguyn t phat ra phtn co bc sng 32 v
khi lectron chuyn t qu ao M sang qu ao K th nguyn t phat ra phtn co bc
sng 31. Biu thc xac inh 31 l
A. 32 213121 32
B. 31 32 21 C. 31 32 21 D.
32 2131
21 32
Hng dn
21 323 1 3 2 2 1 3131 32 21 21 32
hc hc hcE E E E E E
Chn D.
Cu 25: (H2010) Theo mu nguyn t Bo, bn knh qu ao K ca lectron trong
nguyn t hir la r0. Khi lectron chuyn t qu ao N v qu ao L th bn knh qu ao
giam bt
Tuyet pham cong pha Vat l GNTC tren kenh VTV2 Chu Van Bien
10
A. 12r0. B. 4r0. C. 9r0. D. 16r0.
Hng dn
Bn knh qu ao N v L ln lt:
2
0
02
0
412
2
N
N L
L
r rr r r
r r
Chn A.
Cu 26: (H2010) Chum tia X phat ra t mt ng tia X (ng Cu-lit-gi) co tn s ln
nht la 6,4.1018
Hz. Bo qua ng nng cac lectron khi bc ra khoi catt. Hiu in th
gia ant va catt cua ng tia X la
A. 2,65 kV. B. 26,50 kV. C. 5,30 kV. D. 13,25 kV.
Hng dn
326 50 10maxmaxe U e U hf
e U hf f f U , . Vh h e
Chn B.
Ht nhn
Cu 27: (H-2010) Phng xa v phn hach hat nhn
A. u c s hp th ntron chm.
B. u l phan ng hat nhn thu nng lng.
C. u khng phai l phan ng hat nhn.
D. u l phan ng hat nhn toa nng lng.
Hng dn
Phng xa v phn hach hat nhn u l phan ng hat nhn toa nng lng
Chn D.
Cu 28: (H-2010) Mt hat co khi lng nghi m0. Theo thuyt tng i, ng nng
ca hat nay khi chuyn ng vi tc 0,6c (c la tc anh sang trong chn khng) la
A. 0,36m0c2 B. 1,25 m0c
2 C. 0,225m0c
2 D. 0,25m0c
2
Hng dn
2 20 0 0 02
2
1,25 0,25
1
d
mm m W m m c m c
v
c
Chn D.
Cu 29: (H - 2010) Cho ba hat nhn X, Y v Z c s nucln tng ng l AX, AY, AZ
vi AX = 2AY = 0,5AZ. Bit nng lng lin kt ca tng hat nhn tng ng la EX,
EY, EZ vi EZ < EX < EY. Sp xp cc hat nhn ny theo th t tnh bn vng
giam dn l
A. Y, X, Z. B. Y, Z, X. C. X, Y, Z. D. Z, X, Y.
Hng dn
t AX = 2AY = 0,5AZ = a th
0,5
2
Y YY
Y
X XX Y X Z
X
Z ZZ
Z
E E
A a
E E
A a
E E
A a
Chn A.
Cty TNHH MTV DVVH Khang Viet
11
Cu 30: (H 2010) Cho khi lng ca prtn; ntron; 40
18 Ar ; 6
3 Li ln lt l:
1,0073 u; 1,0087 u; 39,9525 u; 6,0145 u v 1 u = 931,5 MeV/c2. So vi nng lng lin
kt ring ca hat nhn 6
3 Li th nng lng lin kt ring ca hat nhn 40
18 Ar
A. ln hn mt lng l 5,20 MeV. B. ln hn mt lng l 3,42 MeV.
C. nho hn mt lng l 3,42 MeV. D. nho hn mt lng l 5,20 MeV.
Hng dn
p dng cng thc:
2
( )W p n Xlk
Zm A Z m m c
A A
931,5
2
Ar
18.1,0073 40 18 1,0087 39,9525
8,62 /
40
uc
MeV nuclon
931,5
2
3.1,0073 6 3 1,0087 6,0145
5,20 /
6Li
uc
MeV nuclon
Ar
8,62 5,20 3,42Li
MeV Chn B.
Cu 31: (H-2010) Dung mt prtn co ng nng 5,45 MeV bn vao hat nhn 4Be9
ang ng yn. Phan ng tao ra hat nhn X va hat . Hat bay ra theo phng vung
goc vi phng ti ca prtn va co ng nng 4 MeV. Khi tinh ng nng cua cac
hat, ly khi lng cac hat tinh theo n vi khi lng nguyn t bng s khi cua
chung. Nng lng toa ra trong cac phan ng nay bng
A. 4,225 MeV. B. 1,145 MeV. C. 2,125 MeV. D. 3,125 MeV.
Hng dn
1 9 4 61 4 2 3H Be X . Hat bay ra theo phng vung goc vi phng ti cua
prtn nn: W W W 1.5,45 4.4 6.WH H X X Xm m m
W 3,575X MeV
Nng lng phan ng:
W W W 4 3,575 5,45 0 2,125 0X H BeE W MeV
Chn C.
Kinh nghim gii nhanh: A B C D
* Nu C Dv v
th C C D D A Am W m W m W
* Nu C Av v
th C C A A D Dm W m W m W
Sau o, kt hp vi C D AE W W W
Vi mi bi ton c th, phai xac inh r u la hat A, hat B, hat C v hat D.
Tuyet pham cong pha Vat l GNTC tren kenh VTV2 Chu Van Bien
12
Cu 32: (H-2010) Hat nhn 210
84 Po ang ng yn th phng xa , ngay sau phng xa
o, ng nng ca hat
A. ln hn ng nng ca hat nhn con.
B. ch c th nho hn hoc bng ng nng ca hat nhn con.
C. bng ng nng ca hat nhn con.
D. nho hn ng nng ca hat nhn con.
Hng dn
210 20684 82P Pb
Cch 1: Trong phng xa, ng nng cc hat sinh ra t l nghich vi khi lng:
1Pb PbPb
W mW W
W m
Chn A.
Cch 2: 2 2
0 W WPb Pb Pb Pb Pb Pbm v m v m v m v m m
1Pb PbPb
W mW W
W m
Chn A.
Cu 33: Ban u co N0 hat nhn ca mt mu cht phong xa nguyn cht co chu ki ban
ra T. Sau khoang thi gian t = 0,5T, k t thi im ban u , s hat nhn cha bi phn
ra ca mu cht phong xa nay la
A. N0/ 2 . B. N0/4. C. N0 2 . D. N0/2.
Hng dn
ln 2 ln 2. .0,5
00 0
2
t TT T
NN N e N e
Chn A.
Cu 34: Bit ng vi phong xa 14
6 C co chu k ban ra 5730 nm. Gia s mt mu g c
co phong xa 200 phn ra/phut va mt mu g khac cung loai , cung khi lng cua
mu g c o, ly t cy mi cht, co phong xa 1600 phn ra/phut. Tui cua mu g
c a cho la
A. 17190 nm. B. 2865 nm. C. 11460 nm. D. 1910 nm.
Hng dn
0200 1ln 2
1600 800
1ln ln8. 5730. 17190
ln 2 ln 2
Ht
HT
H
HH H e t T t (nm)
2. NM 2011
Sng c hc
Cu 1: (H 2011): Pht biu nao sau y la ung khi noi v song c?
A. Bc sng l khoang cch gia hai im trn cng mt phng truyn sng m
dao ng tai hai im o cung pha.
B. Sng c truyn trong cht rn lun l sng dc.
Cty TNHH MTV DVVH Khang Viet
13
C. Sng c truyn trong cht long lun l sng ngang.
D. Bc sng l khoang cch gia hai im gn nhau nht trn cng mt phng
truyn song ma dao ng tai hai im o cung pha.
Hng dn
Bc sng l khoang cch gia hai im gn nhau nht trn cng mt phng
truyn song ma dao ng tai hai im o cung pha Chn D.
Cu 2: (H-2011) mt cht long c hai ngun sng A, B cch nhau 18 cm, dao
ng theo phng thng ng vi phng trnh la uA = uB = acos50t (vi t tnh bng
s). Tc truyn sng ca mt cht long l 50 cm/s. Gi O la trung im ca AB, im
M mt cht long nm trn ng trung trc ca AB v gn O nht sao cho phn t
cht long tai M dao ng cng pha vi phn t cht long tai O. Khoang cch MO l
A. 10 cm. B. 2 10 cm. C. 2 2 cm. D. 2 cm.
Hng dn
Ch : lch pha dao ng ca M so vi O
l /2
M O d AO
.
*M dao ng cng pha vi O khi M/O =
k.2 mind AO k d AO
Cch 1: im M gn O nht dao ng cng pha
vi O:
min min 11d AO d cm 2 2 2 10minMO d AO cm Chn B.
Cch 2:
2 2
9 4 5
2 10
AO BO cm , O
MO MA AO cm
dao ng ngc pha vi A, B.
M gn O nht dao ng cng pha vi O (tc l ngc pha vi ngun) th
MA = MB = 5,5 =11 cm
Cu 3: (H-2011) Mt sng hnh sin truyn theo phng Ox t ngun O vi tn s
20Hz, c tc truyn sng nm trong khoang t 0,7 m/s n 1 m/s. Gi A v B l hai
im nm trn Ox, cng mt pha so vi O v cch nhau 10 cm. Hai phn t mi
trng tai A va B lun dao ng ngc pha vi nhau. Tc truyn sng l
A. 100 cm/s. B. 80 cm/s. C. 85 cm/s. D. 90 cm/s.
Hng dn
2 2 4
2 12 1
d dfk v m / s
v k
. Thay vao iu kin
0,7m/s < v < 1 m/s 1 5 2 35 2 0 8, k , k v , m / s BChn .
Cu 4: (H-2011) Mt si dy an hi cng ngang, hai u c inh. Trn dy c sng
dng, tc truyn song khng i. Khi tn s sng trn dy l 42 Hz th trn dy c
4 im bng. Nu trn dy co 6 im bng th tn s sng trn dy l
A. 252 Hz. B. 126 Hz. C. 28 Hz. D. 63 Hz.
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14
Hng dn
42 2 '
1 ' 632 3
62 '
vl
f fl k f Hz
v fl
f
Chn D.
Cu 5: (H-2011) Mt si dy an hi cng ngang, ang co song dng n inh. Trn
dy, A l mt im nt, B l mt im bng gn A nht, C la trung im ca AB, vi
AB = 10 cm. Bit khoang thi gian ngn nht gia hai ln ma li dao ng ca phn
t tai B bng bin dao ng ca phn t tai C l 0,2 s. Tc truyn sng trn dy l
A. 2 m/s. B. 0,5 m/s. C. 1 m/s. D. 0,25 m/s.
Hng dn
min
10 40 0,44
2 0,2 0,88 8 4
AB cm m
T TAC BC t t t T s
0,5 / v m sT
Chn B.
Cu 6: (H-2011)Mt ngun im O pht sng m c cng sut khng i trong mt
mi trng truyn m ng hng v khng hp th m. Hai im A, B cch ngun m ln
lt l r1 v r2. Bit cng m tai A gp 4 ln cng m tai B. T s r2/r1 bng
A. 4. B. 0,5. C. 0,25. D. 2.
Hng dn
2
1 2 2
2
2 1 1
24
I r rWI
r I r r
Chn D.
Dao ng v sng in t
Cu 7: (H-2011) Nu ni hai u oan mach gm cun cam thun L mc ni tip vi
in tr thun R = 1 vo hai cc ca ngun in mt chiu c sut in ng khng
Cty TNHH MTV DVVH Khang Viet
15
i va in tr trong r th trong mach co dng in khng i cng I. Dng ngun
in nay nap in cho mt t in co in dung C = 2.10-6
F. Khi in tch trn t
in at gi tri cc ai, ngt t in khoi ngun ri ni t in vi cun cam thun L
thnh mt mach dao ng th trong mach co dao ng in t t do vi chu k bng
.10-6
s va cng dng in cc ai bng 8I. Gi tri ca r bng
A. 0,25 . B. 1 . C. 0,5 . D. 2 .
Hng dn
Nu lc u dng ngun in mt chiu c sut in ng E v in tr trong r cho
dng in chy qua R th E
Ir R
. Sau , dng ngun in ny cung cp nng
lng cho mch LC bng cch np in cho t th U0 = E v
0 0 0I Q CU CE .
Suy ra: 0I
C r RI
, vi 2 1
2 fT LC
.
Tn s gc: 66
2 22 10
10. rad / s
T .
.
p dng 6 60 8 2 10 2 10 1I
C r R . . . RI
1R Chn B.
Cu 8: (H-2011) Mt mach dao ng LC li tng gm cun cam thun co t cam
50 mH v t in co in dung C. Trong mach ang co dao ng in t t do vi
cng dng in i = 0,12cos2000t (i tnh bng A, t tnh bng s). thi im m
cng dng in trong mach bng mt na cng hiu dng th hiu in th
gia hai ban t co ln bng
A. 12 3 V. B. 5 14 V. C. 6 2 V. D. 3 14 V.
Hng dn
6 02 2 3
1 15.10 ;
2000 .50.10 2 2 2
IIC H i
L
2
2 2 2 2 2 2 00 0 0
1 1 1
2 2 2 8
IL LW LI Cu Li u I i I
C C
37
2000.50.10 3 148
u V Chn D.
Cu 9: (H 2011): Phat biu nao sau y la sai khi ni v song in t?
A. Khi song in t gp mt phn cch gia hai mi trng th n c th bi phan xa
v khc xa.
B. Song in t truyn c trong chn khng.
C. Song in t l sng ngang nn n ch truyn c trong cht rn.
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16
D. Trong song in t th dao ng ca in trng v ca t trng tai mt im
lun ng pha vi nhau.
Hng dn
Song in t truyn c trong cac mi trng vt cht v ca trong chn khng
Chn C.
Cu 10: (H-2011) Trong mach dao ng LC li tng ang co dao ng in t t do.
Thi gian ngn nht nng lng in trng giam t gi tri cc ai xung cn mt
na gi tri cc ai l 1,5.10-4
s. Thi gian ngn nht in tch trn t giam t gi tri
cc ai xung cn mt na gi tri o la
A. 2.10-4
s. B. 6.10-4
s. C. 12.10-4
s. D. 3.10-4
s.
Hng dn
Thi gian ngn nht nng lng in trng giam t gi tri cc ai (gia s lc
ny q = Q0) xung cn mt na gi tri cc ai (q = Q0/ 2 ) l T/8 = 1,5.10-4
s, suy ra T
= 1,2.10-3
s.
Thi gian ngn nht in tch trn t giam t gi tri cc ai xung cn mt na
gi tri o la T/6 = 2.10-4
(s) Chn A.
Cu 11: (H-2011) Mach dao ng in t LC gm mt cun dy co t cam 50
mH v t in co in dung 5 F. Nu mach co in tr thun 10-2
, duy tr dao
ng trong mach vi hiu in th cc ai gia hai ban t in l 12 V th phai cung
cp cho mach mt cng sut trung bnh bng
A. 72 mW. B. 72 W. C. 36 W. D. 36 mW.
Hng dn
2 2 220 0 00
2 6 22 2 600 3
2 2
1 1 1 5 10 1210 72 10
2 2 2 50 10cc
CU LI CUW I
L
CU . .P I R . .R . . . W
L .
Chn B.
Sng nh sng
Cu 12: (H 2011): Tia Rn-ghen (tia X) c
A. cng ban cht vi tia t ngoai.
B. tn s nho hn tn s ca tia hng ngoai.
C. in tch m nn n bi lch trong in trng v t trng.
D. cng ban cht vi sng m.
Hng dn
Tia Rn-ghen (tia X), tia t ngoai, tia hng ngoai, nh sng nhn thy, sng v
tuyn c cng ban cht la song in t Chn A.
Cu 13: (H - 2011): Mt lng kinh co goc chit quang A = 60 (coi l gc nho) c t trong khng kh. Chiu mt chm nh sng trng song song, hp vo mt bn ca
lng kinh theo phng vung goc vi mt phng phn gic ca gc chit quang, rt gn
canh ca lng kinh. t mt man E sau lng kinh, vung goc vi phng ca chm tia
ti v cch mt phng phn gic ca gc chit quang 1,2 m. Chit sut ca lng kinh
i vi anh sang o l n = 1,642 va i vi nh sng tm l nt = 1,685. rng t mu
o n mu tm ca quang ph lin tc quan sat c trn mn l
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17
A. 4,5 mm. B. 36,9 mm. C. 10,1 mm. D. 5,4 mm.
Hng dn
Ch : Nu lng knh c gc chit quang b v gc ti b th
d d
t t
D n 1 AD n 1 A
D n 1 A
t d t dD D n n A rng quang ph lc ny:
t d t d t dDT IO tan D tan D IO D D IO n n A
Thay s: 0
3
t d 0
6DT IO n n A 1,2 1,685 1,642 5,4.10 m
180
Chn D.
Cu 14: (H-2011) Chiu t nc ra khng kh mt chm tia sng song song rt hp
(coi nh mt tia sng) gm 5 thnh phn n sc: tim, lam, o, lc, vang. Tia lo n
sc mu lc i la la mt nc (st vi mt phn cch gia hai mi trng). Khng k
tia n sc mu lc, cc tia l ra ngoai khng khi la cac tia n sc mu
A. tim, lam, o. B. o, vng, lam. C. o, vng. D. lam, tm.
Hng dn
1 1 1 1 1
sindo vang luc lam tim
in n n n n
b phn x ton phnkhc x ra ngoi khng kh
Chn C.
Cu 15: (H 2011): Trong th nghim Y ng v giao thoa nh sng, nu thay nh
sang n sc mu lam bng anh sang n sc mu vng v gi nguyn cac iu kin
khc th trn mn quan st:
A. Khoang vn tng ln. B. Khoang vn giam xung.
C. vi tri vn trung tm thay i. D. Khoang vn khng thay i.
Hng dn
V vng > lam nn v lam
v lam
D Di i
a a
Chn A.
Cu 16: (H 2011): Trong th nghim Y-ng v giao thoa nh sng, khe hp S pht
ra ng thi ba bc xa n sc co bc sng l 1 = 0,42 m, 2 = 0,56 m v 3 =
0,63 m. Trn mn, trong khoang gia hai vn sng lin tip c mu ging mu vn
trung tm, nu hai vn sng ca hai bc xa trng nhau ta ch tnh l mt vn sng th s
vn sang quan sat c l
A. 21. B. 23. C. 26. D. 27.
Hng dn
1
231 21 2 3
3
2
0,56 4 12
0,42 3 9
0,56 8
0,63 9
k
kDD Dx k k k
ka a a
k
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18
1
2
3
12
9
8
k
k
k
Nu khng trng c 11
Nu khng trng c 8
Nu khng trng c 7
1
2
1
3
3
2
4 8 12
3 6 9
3 6 9 12
2 4 6 8
8
9
k
k
k
k
k
k
H 1 trng vi h 2 2 v tr khc :
H 1 trng vi h 3 3 v tr khc :
H 2 trng vi h 3 0 v tr khc :
H 1 ch cn 11- 2 - 3 = 6
H 2 ch cn 8 - 2 = 6
H 3 ch cn 7 - 3 = 4
Tng s vch sng 11+ 8 +7 - 2 - 3 -0 = 21
Chn A.
Cu 17: (H-2011): Trong th nghim Y-ng v giao thoa anh sang, hai khe c
chiu bng anh sang n sc, khoang cch gia hai khe l 0,6 mm. Khoang vn trn
man quan sat o c l 1 mm. T vi tri ban u, nu tinh tin mn quan st mt oan
25 cm lai gn mt phng cha hai khe th khoang vn mi trn man la 0,8 mm. Bc
sng ca nh sng dng trong th nghim l
A. 0,64 m. B. 0,50 m. C. 0,45 m. D. 0,48 m.
Hng dn
6
0 250 48 10
0 25 0 25
Di
a i i'. ,ai i' , . m
D , a ,i'
a
Chn A.
Lng t nh sng
Cu 18: (H- 2011 trng vi C 2007) Cng thoat lectrn (lectron) ra khoi mt kim
loai l A = 1,88 eV. Bit hng s Plng h = 6,625.10-34
J.s, vn tc nh sng trong chn
khng c = 3.108 m/s v 1 eV = 1,6.10
-19 J. Gii han quang in ca kim loai o la
A. 550 nm. B. 220 nm. C. 1057 nm. D. 661 nm.
34 8
9
0 19
6,625.10 .3.10: 661.10
1,88.1,6.10
hcHD m
A
Chn D.
Cu 19: (H 2011): Khi lectron qu ao dng th n th nng lng ca nguyn t
hir c xac inh bi cng thc En = -13,6/n2 (eV) (vi n = 1, 2, 3,). Khi lectron
trong nguyn t hir chuyn t qu ao dng n = 3 v qu ao dng n = 1 th nguyn
t phat ra phtn co bc sng 1. Khi lectron chuyn t qu ao dng n = 5 v qu
ao dng n = 2 th nguyn t phat ra phtn co bc sng 2. Mi lin h gia hai
bc sng 1 v 2 l
Cty TNHH MTV DVVH Khang Viet
19
A. 272 = 1281. B. 2 = 51. C. 1892 = 8001. D. 2 = 41.
Hng dn
3 1 2 2
1 2
15 2 2 2
2
13,6 13,6 813,6.
3 1 9 800
13,6 13,6 21 18913,6.
5 2 100
hcE E
hcE E
Chn C.
Cu 20: (H 2011): Nguyn tc hoat ng ca quang in tr da vo
A. hin tng tn sc nh sng. B. hin tng quang in ngoi.
C. hin tng quang in trong. D. hin tng pht quang ca cht rn.
Hng dn
Nguyn tc hoat ng ca quang in tr da vo hin tng quang in trong
Chn C.
Cu 21: (H 2011): Trong nguyn t hir, ban kinh Bo la r0 = 5,3.10-11
m. mt
trang thi kch thch ca nguyn t hir, lectron chuyn ng trn qu ao dng c
bn knh l r = 2,12.10-10
m. Qu ao o co tn gi l qu ao dng
A. L. B. O. C. N. D. M.
Hng dn
T cng thc r = n2r0 suy ra n = 2, qu ao dng ny c tn l qu ao L Chn A.
Cu 22: (H-2011) Mt cht phat quang c kch thch bng anh sang co bc sng
0,26 m th phat ra anh sang co bc sng 0,52 m. Gia s cng sut ca chm sng
pht quang bng 20% cng sut ca chm sng kch thch. T s gia s phtn nh
sng pht quang v s phtn nh sng kch thch trong cng mt khoang thi gian l
A. 4/5. B. 1/10. C. 1/5. D. 2/5.
Hng dn
'W ' ' ' 0,26 ' 2'0,2 . .W ' 0,52 5
hcN
N N N
hc N N NN
Chn D.
Cu 23: (H 2011): Hin tng quang in ngoi l hin tng lectron bi bt ra
khoi tm kim loai khi
A. chiu vo tm kim loai ny mt chm hat nhn heli.
B. chiu vo tm kim loai ny mt bc xa in t co bc sng thch hp.
C. cho dng in chay qua tm kim loai ny.
D. tm kim loai ny bi nung nng bi mt ngun nhit.
Hng dn
Hin tng quang in ngoi l hin tng lectron bi bt ra khoi tm kim loai khi
chiu vo tm kim loai ny mt bc xa in t co bc sng thch hp Chn B.
Ht nhn
Cu 24: (H2011): Gia s trong mt phan ng hat nhn, tng khi lng ca cc hat
trc phan ng nho hn tng khi lng cc hat sau phan ng l 0,02 u.
Bit 1u = 931,5 MeV/c2. Phan ng hat nhn ny
Tuyet pham cong pha Vat l GNTC tren kenh VTV2 Chu Van Bien
20
A. thu nng lng 18,63 MeV. B. thu nng lng 1,863 MeV.
C. toa nng lng 1,863 MeV. D. toa nng lng 18,63 MeV.
Hng dn
2 20,02 18,63t sE m m c uc MeV Chn A.
Cu 25: (H2011): Bn mt prtn vo hat nhn 7
3 Li ng yn. Phan ng tao ra hai
hat nhn X ging nhau bay ra vi cng tc va theo cac phng hp vi phng ti
ca prtn cc gc bng nhau l 600. Ly khi lng ca mi hat nhn tinh theo n vi
u bng s khi ca n. T s gia tc ca prtn v tc ca hat nhn X l
A. 4. B. 1/4. C. 2. D. 1/2.
Hng dn
1 7 4 4
1 3 2 2H Li X X
p dng inh lut bao toan ng lng: 1 1p p X X X Xm v m v m v
2 2 2
1 2 1 22 cosp p X X X X X X X Xm v m v m v m v m v
042 2cos 2 2cos120 4
1
p X
X p
v m
v m Chn A.
Cu 25: (H2011): Khi ni v tia , pht biu nao sau y sai?
A. Tia khng phai la song in t.
B. Tia c kha nng m xuyn manh hn tia X.
C. Tia khng mang in.
D. Tia c tn s ln hn tn s ca tia X.
Hng dn
Tia c ban cht la song in t Chn A.
Cu 26: (H2011): Cht phng xa plni 210
84 Po pht ra tia v bin i thnh ch 206
82 Pb . Cho chu k bn r ca 210
84 Po la 138 ngay. Ban u (t = 0) c mt mu plni
nguyn cht. Tai thi im t1, t s gia s hat nhn plni v s hat nhn ch trong
mu l 1/3. Tai thi im t2 = t1 + 276 ngy, t s gia s hat nhn plni v s hat
nhn ch trong mu l
A. 1/15. B. 1/16. C. 1/9. D. 1/25.
Hng dn
n thi im t, s hat nhn Po210 cn lai v s hat nhn ch Pb208 tao thnh ln
lt l:
ln 2
0
ln 2
0 1
tT
Po
tT
Pb
N N e
N N N e
ln 2
1t
Pb T
Po
Ne
N
1 1
1
2 1
2
ln 2 ln 2
ln 2 ln 2276
1 3 4
1 1
t tPb T T
Po t
t tPb T T
Po t
Ne e
N
Ne e
N
Cty TNHH MTV DVVH Khang Viet
21
1
2 2
ln 21
.4 1 1515
tPb PoT
Po Pbt t
N Ne
N N
Chn A.
Cu 27: (H2011): Theo thuyt tng i, mt lectron co ng nng bng mt na
nng lng ngh ca n th lectron ny chuyn ng vi tc bng
A. 2,41.108 m/s. B. 2,75.10
8 m/s. C. 1,67.10
8 m/s. D. 2,24.10
8 m/s.
Hng dn
2 2 2 0
0 0 0 0 02
2
1 12 3 2 3
2 21
d
mW E mc m c m c m m m
v
c
2
8
2
2 51 2 24 10
3 3
v cv , . m / s
c Chn D.
Cu 28: (H 2011) Mt hat nhn X ng yn, phng xa v bin thnh hat nhn Y.
Gi m1 v m2, v1 v v2, K1 v K2 tng ng l khi lng, tc , ng nng ca hat
v hat nhn Y. H thc nao sau y la ung?
A. 1 1 1
2 2 2
v m K
v m K . B. 2 2 2
1 1 1
v m K
v m K . C. 1 2 1
2 1 2
v m K
v m K . D. 1 2 2
2 1 1
v m K
v m K .
Hng dn
Hat nhn m A ng yn phng xa thnh hai hat B (hat nhn con) v C (hat phng
xa): X Y + . p dng inh lut bao toan ng lng va inh lut bao toan nng
lng ton phn: 2 2
0 Y Y Y Y
C BX Y Y
m v m v m v m v
K K Em c K K m m c
Y Y Y Y
Y Y
m K m K mK v
K K E K v m
Nhn xt: Hai hat sinh ra chuyn ng theo hai hng ngc nhau, c tc v
ng nng t l nghich vi khi lng Chn C.
3. NM 2012
Sng c hc
Cu 1: Mt sng m v mt sng nh sng truyn t khng khi vao nc th bc sng
A. ca song m tng cn bc sng ca sng nh sng giam.
B. ca sng m giam cn bc sng ca sng anh sang tng.
C. ca song m va song anh sang u giam.
D. ca song m va song anh sang u tng.
Hng dn
Mt sng m v mt sng nh sng truyn t khng khi vao nc th bc sng
ca song m tng (v tc truyn song tng) cn bc sng ca sng nh sng giam
(v tc truyn sng giam) Chn A.
Tuyet pham cong pha Vat l GNTC tren kenh VTV2 Chu Van Bien
22
Cu 2: Khi ni v s truyn song c trong mt mi trng, pht biu nao sau y ung?
A. Nhng phn t ca mi trng cch nhau mt s nguyn ln bc sng th dao
ng cng pha.
B. Hai phn t ca mi trng cch nhau mt phn t bc song th dao ng lch
pha nhau 900.
C. Nhng phn t ca mi trng trn cng mt hng truyn sng v cch nhau
mt s nguyn ln bc song th dao ng cng pha.
D. Hai phn t ca mi trng cch nhau mt na bc song th dao ng ngc pha.
Hng dn
Nhng phn t ca mi trng trn cng mt hng truyn sng v cch nhau mt
s nguyn ln bc song th dao ng cng pha Chn A.
Cu 3: (H-2012) Trn mt si dy cng ngang vi hai u c inh ang co song
dng. Khng xet cac im bng hoc nt, quan st thy nhng im co cung bin
v gn nhau nht th u cach u nhau 15 cm. Bc sng trn dy c gi tri bng
A. 30 cm. B. 60 cm. C. 90 cm. D. 45 cm.
Hng dn
Nu cac im trn dy co cung bin A0 v nm cach u nhau nhng khoang x
th x = MN = NP ax
0 ax
8 4
2sin
8 2
mm
x y x
AA A
15 604 4
x cm cm
Chn B.
Cu 4: (H - 2012) Hai im M, N cng nm trn mt hng truyn sng v cch
nhau mt phn ba bc song. Bin song khng i trong qu trnh truyn. Tai mt
thi im, khi li dao ng ca phn t tai M la 3 cm th li dao ng ca phn t
tai N l -3 cm. Bin sng bng
A. 6 cm. B. 3 cm. C. 2 3 cm D. 3 2 cm.
Hng dn
Cch 1: Bi ton khng ni r sng truyn theo hng no nn ta gia s truyn qua M
ri mi n N v biu din nh hnh v. M va N i xng nhau qua I nn MI = IN = /6.
Cty TNHH MTV DVVH Khang Viet
23
thi im hin tai I vi tr cn bng nn 2
AsinMx
u
hay
2
3 sin 2 36
A A cm
CChn .
Cch 2: Gia s sng truyn qua M ri
n N th dao ng tai N tr pha hn
2 2
3
d
3
cos 3 cos M
u A t tA
29
sin
A
tA
23 9
2 2 2cos 3 cos cos sin sin 3
3 3 3N
A
u A t A t A t
2 3A cm
Cch 3: Dao ng tai M sm pha hn dao ng tai N: 2 2
3
d
T hnh v tinh c 6
v 2 3
cos
MuA cm
Cu 5: (H -2012) Trn mt s dy an hi di 100 cm vi hai u A v B c inh
ang co song dng, tn s sng l 50 Hz. Khng k hai u A v B, trn dy c 3 nt
sng. Tc truyn sng trn dy l
A. 15 m/s. B. 30 m/s. C. 20 m/s. D. 25 m/s.
Hng dn
Trn dy c 5 nt, tc l c 4 bng: 4 2 25 /2 2
v lfl v m s
f
Chn D.
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Cu 6: (H-2012) Tai im O trong mi trng ng hng, khng hp th m, c 2
ngun m im, ging nhau vi cng sut phat m khng i. Tai im A c mc
cng m 20 dB. tai trung im M ca oan OA c mc cng m l 30 dB
th s ngun m ging cc ngun m trn cn t thm tai O bng
A. 4. B. 3. C. 5. D. 7.
Hng dn
Nu ngun m c cu tao t n ngun m ging nhau mi ngun c cng sut P0
th cng sut ca ngun P = nP0. p dng:
020 2 2
00 2 2
104 4
10
104 4
L
L' L
L'
nPPI I .
n' rr r
n' PP' n r'I ' I .
r' r'
2
23 210 10 2 5 5 2 32
L' L n' r n' n' nn r'
Chn B.
Cu 6: (H-2012) Trong hin tng giao thoa song nc, hai ngun dao ng theo
phng vung goc vi mt nc, cung bin , cng pha, cng tn s 50 Hz c t
tai hai im S1 v S2 cch nhau 10 cm. Tc truyn sng trn mt nc l 75 cm/s.
Xet cac im trn mt nc thuc ng trn tm S1, bn knh S1S2, im m phn t
tai o dao ng vi bin cc ai cach im S2 mt oan ngn nht bng
A. 85 mm. B. 15 mm. C. 10 mm. D. 89 mm.
Hng dn
Bc sng: 1,5v
cmf
Hai ngun kt hp cung pha, ng trung trc l cc
ai gia, hai cc ai xa nht nm hai bn ng trung
trc c hiu ng i MS1 MS2 = -n (M gn S1 hn)
v MS1 MS2 = n (M gn S2 hn);
vi n l s nguyn ln nht thoa mn
1 2S S
n
10
6,67 61,5
n .
Do o, 10 MS2 = 6.1,5 MS2 = 1 cm Chn C.
Dao ng v sng in t
Cu 7: (H-2012) Khi ni v song in t, pht biu nao sau y la sai?
A. Song in t mang nng lng.
B. Song in t tun theo cc quy lut giao thoa, nhiu xa.
C. Song in t l sng ngang.
D. Song in t khng truyn c trong chn khng.
Cty TNHH MTV DVVH Khang Viet
25
Hng dn
Song in t lan truyn c trong mi trng vt cht v ca trong chn khng
Chn D.
Cu 8: (H-2012) Tai H Ni, mt may ang phat song in t. Xt mt phng
truyn co phng thng ng hng ln. Vo thi im t, tai im M trn phng
truyn, vect cam ng t ang co ln cc ai va hng v pha Nam. Khi o vect
cng in trng c
A. ln cc ai va hng v pha Ty.
B. ln cc ai va hng v phia ng.
C. ln bng khng.
D. ln cc ai va hng v pha Bc.
Hng dn
Trong song in t th dao ng ca in trng
v ca t trng tai mt im lun lun ng pha vi
nhau. Khi vec t cam ng t co ln cc ai th
vec t cng in trng cng co ln cc ai.
Song in t l sng ngang: E B c (theo
ung th t hp thnh tam din thun). Khi quay t
E
sang B
th chiu tin ca inh c l c
.
Nga bn tay phai theo hng truyn song (hng thng ng di ln), ngn ci
hng theo E
th bn ngon hng theo B Chn A.
Cu 9: (H-2012) Mt mach dao ng in t li tng ang co dao ng in t t
do. Bit in tch cc ai trn mt ban t in l 4 2 C va cng dng in cc
ai trong mach l 0,5 2 A. Thi gian ngn nht in tch trn mt ban t giam t
gi tri cc ai n na gi tri cc ai l
A. 4/3 s. B. 16/3 s. C. 2/3 s. D. 8/3 s.
Hng dn
Tn s gc = I0/Q0 = 125000 rad/s, suy ra T = 2/ = 1,6.10-5
s = 16 s.
Thi gian ngn nht in tch trn mt ban t giam t gi tri cc ai Q0 n na
gi tri cc ai 0,5Q0 l T/6 = 8/3 s Chn D.
Cu 10: (H-2012) Mt mach dao ng gm mt cun cam thun co t cam xc
inh v mt t in l t xoay, co in dung thay i c theo quy lut hm s bc
nht ca gc xoay ca ban linh ng. Khi = 00, tn s dao ng ring ca mach l
3 MHz. Khi =1200, tn s dao ng ring ca mach la 1 MHz. mach ny c tn
s dao ng ring bng 1,5 MHz th bng
A. 300. B. 45
0. C. 60
0. D. 90
0.
Tay
phai
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Hng dn
Ch :
1) T h thc: 3 1 3 11 1
2 1 2 1 2 1 2 1
C CC C
C C C C
.
2) T cng thc: 2 2 2
1 1
4C
L f L , C t l vi f
-2 nn trong h thc trn ta c th
thay C bi f-2
: 2 2
3 1 3 1
2 22 12 1
f f
f f
.
p dng:
2 23 1 3 1
2 22 12 1
f f
f f
2 203
30 2 2
0 1,5 345
120 0 1 3
Chn B.
Cu 11: (H-2012) Trong mt mach dao ng li tng ang co dao ng in t t
do. Gi L la t cam va C la in dung ca mach. Tai thi im t, hiu in th gia
hai ban t in la u va cng dng in trong mach l i. Gi U0 l hiu in th cc
ai gia hai ban t in v I0 la cng dng in cc ai trong mach. H thc lin
h gia u v i l
A. 2 2 20C
i U uL
. B. 2 2 20L
i U uC
C. 2 2 20i LC U u D. 2 2 20i LC U u Hng dn
2 2 2
2 2 200
2 2 2
CU Cu Li CW i U u
L Chn A.
Sng nh sng
Cu 12: (H-2012) Mt anh sang n sc mu cam c tn s f c truyn t chn
khng vo mt cht long c chit sut la 1,5 i vi nh sng ny. Trong cht long
trn, nh sng ny c
A. mu tm v tn s f. B. mu cam v tn s 1,5f.
C. mu cam v tn s f. D. mu tm v tn s 1,5f.
Hng dn
Tn s v mu sc nh sng khng ph thuc vao mi trng, ngha la khi anh sang
truyn t mi trng nay sang mi trng khc th tn s v mu sc khng i
Chn A.
Cu 13: (H-2012) Chiu xin t khng khi vao nc mt chm sng song song rt
hp (coi nh mt tia sng) gm ba thnh phn n sc: o, lam v tm. Gi r, r , rt
ln lt l gc khc xa ng vi tia mau o, tia mu lam v tia mu tm. H thc ung la
A. r = rt = r. B. rt < r < r. C. r < r < rt. D. rt < r < r .
Cty TNHH MTV DVVH Khang Viet
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Hng dn
ro > rda cam > rvng > rlc > rlam > rchm > rtm Chn B.
Cu 14: (H-2012) Khi ni v tnh cht ca tia t ngoai, pht biu nao sau y la sai?
A. Tia t ngoai lm in ha khng kh.
B. Tia t ngoai kch thch s pht quang ca nhiu cht.
C. Tia t ngoai tc dng ln phim anh.
D. Tia t ngoai khng bi nc hp th.
Hng dn
Tia t ngoai bi nc hp th rt manh Chn D.
Cu 15: (H-2012) Trong th nghim Y-ng v giao thoa nh sng, ngun sng pht
ng thi hai anh sang n sc 1, 2 co bc sng ln lt l 0,48 m v 0,60 m.
Trn mn quan st, trong khoang gia hai vn sng gn nhau nht v cng mu vi vn
sng trung tm c
A. 4 vn sng 1 v 3 vn sng 2. B. 5 vn sng 1 v 4 vn sng 2.
C. 4 vn sng 1 v 5 vn sng 2. D. 3 vn sng 1 v 4 vn sng 2.
Hng dn
11 2 21 1 2 2
2 1 1 2
5 1 40,6 5
0,48 4 4 1 3
k ix k i k i
k i
vn sng
vn sng
Chn A.
Cu 15: (H-2012) Trong th nghim Y-ng v giao thoa nh sng, ngun sng pht
ng thi hai anh sang n sc 1, 2 co bc sng ln lt l 0,48 m v 0,60 m.
Trn mn quan st, trong khoang gia hai vn sng gn nhau nht v cng mu vi vn
sng trung tm c
A. 4 vn sng 1 v 3 vn sng 2. B. 5 vn sng 1 v 4 vn sng 2.
C. 4 vn sng 1 v 5 vn sng 2. D. 3 vn sng 1 v 4 vn sng 2.
Hng dn
11 2 21 1 2 2
2 1 1 2
5 1 40,6 5
0,48 4 4 1 3
k ix k i k i
k i
vn sng
vn sng
Chn A.
Cu 15: (H-2012) Trong th nghim Y-ng v giao thoa nh sng, ngun sng pht
ng thi hai anh sang n sc 1, 2 co bc sng ln lt l 0,48 m v 0,60 m.
Trn mn quan st, trong khoang gia hai vn sng gn nhau nht v cng mu vi vn
sng trung tm c
A. 4 vn sng 1 v 3 vn sng 2. B. 5 vn sng 1 v 4 vn sng 2.
C. 4 vn sng 1 v 5 vn sng 2. D. 3 vn sng 1 v 4 vn sng 2.
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Hng dn
11 2 21 1 2 2
2 1 1 2
5 1 40,6 5
0,48 4 4 1 3
k ix k i k i
k i
vn sng
vn sng
Chn A.
Cu 16: (H-2012) Trong th nghim Y-ng v giao thoa vi anh sang n sc c
bc sng , khoang cch gia hai khe hp l a, khoang cch t mt phng cha hai
khe hp n mn quan st l 2 m. Trn mn quan st, tai im M cch vn sng trung
tm 6 mm, c vn sng bc 5. Khi thay i khoang cch gia hai khe hp mt oan
bng 0,2 mm sao cho vi tri vn sang trung tm khng thay i th tai M c vn sng
bc 6. Gi tri ca bng
A. 0,60 m. B. 0,50 m. C. 0,45 m. D. 0,55 m.
Hng dn
V bc vn tng ln nn a tng thm: 5 60 2
M
D Dx
a a ,
65 6
1 0 6 100 2 5
Maxa mm , . ma a , D
Chn A.
Cu 17: (H-2012) Trong th nghim Y-ng v giao thoa nh sng, ngun sng pht ra
anh sang n sc co bc sng 1. Trn mn quan st, trn oan thng MN di 20 mm
(MN vung gc vi h vn giao thoa) c 10 vn ti, M v N l vi tr ca hai vn sng.
Thay nh sng trn bng anh sang n sc co bc sng 2 = 51/3 th tai M l vi tr
ca mt vn giao thoa, s vn sang trn oan MN lc ny l
A.7. B. 5. C. 8. D. 6.
Hng dn
Ta c: 1 2 1 20,6 10 6 6 1 7si i MN i i N Chn A.
(Luc u, M l vn sng nn xM = ki1 = 0,6ki2 (k l s nguyn). V 0,6k khng th l s
ban nguyn c v 0,6k ch c th l s nguyn, tc la sau o tai M vn l vn sng).
Lng t nh sng
Cu 18: (H-2012) Laze A pht ra chm bc xa co bc sng 0,45 m vi cng sut
0,8W. Laze B pht ra chm bc xa co bc sng 0,60 m vi cng sut 0,6 W. T s
gia s phtn ca laze B v s phtn ca laze A pht ra trong mi giy l
A. 1. B. 20/9. C. 2. D. 3/4.
Hng dn
. 1
B
B B B B B
A A A AA
A
hcN
P N PhcP N N
hcP N PN
Chn A.
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29
Cu 19: Theo thuyt lng t nh sng, pht biu nao sau y la sai?
A. Trong chn khng, phtn bay vi tc c = 3.108 m/s dc theo cc tia sng.
B. Phtn ca cac anh sang n sc khac nhau th mang nng lng khc nhau.
C. Nng lng ca mt phtn khng i khi truyn trong chn khng.
D. Phtn tn tai trong ca trang thai ng yn v trang thi chuyn ng.
Hng dn
Phtn ch tn tai trong trang thi chuyn ng m khng tn tai trang thai ng
yn Chn D.
Cu 20: (H-2012) Bit cng thot lectron ca cc kim loai: canxi, kali, bac va ng
ln lt l: 2,89 eV; 2,26 eV; 4,78 eV v 4,14 eV. Chiu anh sang co bc sng 0,33
m vo b mt cc kim loai trn. Hin tng quang in khng xay ra vi cc kim loai
nao sau y?
A. Kali va ng. B. Canxi v bac. C. Bac va ng. D. Kali v canxi.
Hng dn
26
6 19
19,875.10 13,76
0,33.10 1,6.10Ca K
hc eVeV A A
: Gy ra hin tng
quang in cho Ca, K v khng gy hin tng quang in cho Bac va ng Chn C.
Cu 21: (H-2012) Theo mu nguyn t Bo, trong nguyn t hir, chuyn ng ca
lectron quanh hat nhn l chuyn ng trn u. T s gia tc ca lectron trn
qu ao K v tc ca lectron trn qu ao M bng
A. 9. B. 2. C. 3. D. 4.
Hng dn
tm tc electron trn qu o dng th c th lm theo cc cch:
*Khi electron chuyn ng trn qu o n, lc ht tnh in Cu-lng ng vai tr l
lc hng tm:
22 2 22
2
nCL ht n n
n n n n
mvke ke keF F mv v
r r r mr (vi k = 9.10
9
Nm2/C
2) 2 1
1 2
1
2
n n
n n
v r n
v r n
*Nng lng trng thi dng bao gm th nng tng tc v ng nng ca
electron:
2 2 222 2W W
2 2 2
n n n nn t d n n
n
mv mv mv EkeE mv v
r m
p dng 3
1
K
M
n M
n K
v n
v n Chn C.
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Cu 22: (H-2012) Theo mu nguyn t Bo, trong nguyn t hidr, khi lectron
chuyn t qu ao P v qu ao K th nguyn t pht ra phton ng vi bc xa c tn
s f1 . Khi lectron chuyn t qu ao P v qu ao L th nguyn t pht ra phtn ng
vi bc xa c tn s f2. Nu lectron chuyn t qu ao L v qu ao K th nguyn t
pht ra phtn ng vi bc xa c tn s
A. f3 = f1 f2. B. f3 = f1 + f2. C. 2 2
3 1 2f f + f . D. 1 2
3
1 2
f ff
f f
.
Hng dn
Ta thy: EKL = EPK EPL hf3 = hf1 hf2 f 3 = f1 f2 Chn A.
Ht nhn nguyn t
Cu 23: Trong mt phan ng hat nhn, c s bao ton
A. s prtn. B. s nucln. C. s ntron. D. khi lng.
Hng dn
Trong mt phan ng hat nhn, c s bao ton s nucln Chn B.
Cu 24: (H-2012) Phng xa v phn hach hat nhn
A. u l phan ng hat nhn toa nng lng.
B. u l phan ng hat nhn thu nng lng
C. u l phan ng tng hp hat nhn.
D. u khng phai l phan ng hat nhn
Hng dn
Phng xa v phn hach hat nhn u l phan ng hat nhn toa nng lng Chn A.
Cu 25: (H-2012) Hat nhn urani 238
92U sau mt chui phn r, bin i thnh hat
nhn ch 206
82 Pb . Trong qua trnh o, chu k ban ra ca 238
92U bin i thnh hat nhn ch
l 4,47.109 nm. Mt khi a c pht hin c cha 1,188.10
20 hat nhn
238
92U v
6,239.1018
hat nhn 206
82 Pb . Gia s khi a luc mi hnh thnh khng cha ch v tt ca
lng ch c mt trong o u l san phm phn r ca 238
92U . Tui ca khi a khi
c pht hin l
A. 3,3.108 nm. B. 6,3.10
9 nm. C. 3,5.10
7 nm. D. 2,5.10
6 nm.
Hng dn
Gia s khi mi hnh thnh mt hn a, ch c U238, c mi hat U238 phn r tao ra
mt hat Pb206. n thi im t, s hat U238 cn lai v s hat Pb206 tao thnh ln lt
l:
ln 2
0
ln 2
0 1
tT
me
tT
con
N N e
N N e
2
1ln
tcon T
me
Ne
N
Cty TNHH MTV DVVH Khang Viet
31
Cu 26: (H-2012) Tng hp hat nhn heli 4
2 He t phan ng hat nhn
1 7 4
1 3 2H Li He X . Mi phan ng trn toa nng lng 17,3 MeV. Nng lng toa
ra khi tng hp c 0,5 mol heli l
A. 1,3.1024
MeV. B. 2,6.1024
MeV. C. 5,2.1024
MeV. D. 2,4.1024
MeV.
Hng dn
Vit y phng trnh phan ng hat nhn ta nhn thy X cng la 4
2 He :
1 7 4 4
1 3 2 2H Li He X
V vy, c mi phan ng hat nhn c 2 hat 4
2 He tao thanh. Do o, s phan ng hat
nhn bng mt na s hat 4
2 He :
1
. Q E ES phn ng S ht He. 2
23 241
.0,5.6,023.10 .17,3 2,6.102
Q MeV Chn B.
Cu 27: (H 2012) Cac hat nhn teri 2
1H ; triti 3
1 H , heli 4
2 He co nng lng lin
kt ln lt l 2,22 MeV; 8,49 MeV v 28,16 MeV. Cc hat nhn trn c sp xp
theo th t giam dn v bn vng ca hat nhn l
A. 2
1H ; 4
2 He ; 3
1 H . B. 2
1H ; 3
1 H ; 4
2 He .
C. 4
2 He ; 3
1 H ;2
1H . D. 3
1 H ; 4
2 He ; 2
1H .
Hng dn
p dng cng thc:
2
1
3
1
4
2
2,221,11 /
2
W 8,492,83 /
3
28,167,04 /
4
H
lk
H
He
MeV nuclon
MeV nuclon
A
MeV nuclon
4 3 2
2 1 1He H H
Chn C.
Cu 28: (H-2012) Mt hat nhn X, ban u ng yn, phng xa v bin thnh hat
nhn Y. Bit hat nhn X c s khi l A, hat pht ra tc v. Ly khi lng ca hat
nhn bng s khi ca no tinh theo n vi u. Tc ca hat nhn Y bng
A. 4
4
v
A. B.
2
4
v
A. C.
4
4
v
A. D.
2
4
v
A.
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Hng dn
4 4
2 2
A A
Z ZX Y
4
04
Y Y Y Y Y
Y
m v vm v m v m v m v v
m A
Chn C.
4. NM 2013
Sng c hc
Cu 1: (H - 2013): Trn mt si dy an hi dai 1m, hai u c inh, ang co song
dng vi 5 nt sng (k ca hai u dy). Bc sng ca sng truyn trn dy l:
A. 0,5 m. B. 2 m. C. 1 m. D. 1,5 m.
Hng dn
Trn dy c 5 nt, suy ra c 4 b sng: 4 1 0,52
m m
Chn A.
Cu 2: (H - 2013): Trong mt th nghim v giao thoa song nc, hai ngun sng kt
hp dao ng cung pha t tai hai im A v B cch nhau 16 cm. Sng truyn trn mt
nc vi bc song 3 cm. Trn oan AB, s im m tai o phn t nc dao ng vi
bin cc ai l:
A. 9. B. 10. C. 11. D. 12.
Hng dn
S cc ai: 5,3 5,3 5;...;5AB AB
k k k
c 11 gi tr
Chn C.
Cu 3: (H - 2013): Mt ngun phat song dao ng iu ha tao ra song trn ng
tm O truyn trn mt nc vi bc sng . Hai im M v N thuc mt nc, nm
trn hai phng truyn sng m cc phn t nc dao ng. Bit OM = 8; ON = 12
va OM vung goc ON. Trn oan MN, s im m phn t nc dao ng ngc pha
vi dao ng ca ngun O l:
A. 5. B. 6. C. 7. D. 4.
Hng dn
K OH MN, t h thc
2 2 2
1 1 1
OH OM ON tinh c OH = 6,6.
Cac im dao ng ngc pha vi O cch O mt
khoang d = (k + 0,5).
+ S im trn MH: 6,6 (k + 0,5)k 8
6,1 k 7,5 k = 7: co 1 im.
+ S im trn HN: 6,6 < (k + 0,5)k 12
6,1 < k 11,5 k = 7,11: co 5 im.
Tng s im l 6.
Cty TNHH MTV DVVH Khang Viet
33
Cu 4: (H - 2013): Mt
song hnh sin ang truyn
trn mt si dy theo chiu
dng ca trc Ox. Hnh
v m ta hnh dang ca si
dy tai thi im t1 (ng net t) v t2 = t1 + 0,3 (s) (ng lin nt). Tai thi im
t2, vn tc ca im N trn y la
A. -39,3 cm/s. B. 65,4 cm/s. C. -65,4 cm/s. D. 39,3 cm/s.
Hng dn
T hnh v ta thy: Bin sng A = 5 cm.
T 30 cm n 60 cm c 6 nn chiu di mi l (60 30)/6 = 5 cm.
Bc sng bng 8 nn = 8.5 = 40 cm.
Trong thi gian 0,3 s sng truyn i c 3 theo phng ngang tng ng qung
ng 15 cm nn tc truyn sng 15
50 /0,3
v cm s . Chu k sng v tn s gc:
T = /v = 0,8 s; = 2/T = 2,5 (rad/s).
Tai thi im t2, im N qua vi tr cn bng v nm sn trc nn no ang i
ln vi tc cc ai, tc l vn tc ca no dng va co ln cc ai:
vmax = A = 2,5.5 39,3 cm/s Chn D.
Cu 5: (H - 2013): Trong mt th nghim v giao thoa song nc, hai ngun kt hp
O1 v O2 dao ng cng pha, cng bin . Chn h trc ta vung gc xOy thuc
mt nc vi gc ta l vi tri t ngun O1 cn ngun O2 nm trn trc Oy. Hai
im P v Q nm trn Ox c OP = 4,5 cm v OQ = 8 cm. Dich chuyn ngun O2 trn
trc Oy n vi tr sao cho gc PO2Q c gi tri ln nht th phn t nc tai P khng
dao ng cn phn t nc tai Q dao ng vi bin cc ai. Bit gia P v Q khng
cn cc ai nao khac. Trn oan OP, im gn P nht m cc phn t nc dao ng
vi bin cc ai cch P mt oan l:
A. 3,4 cm. B. 2,0 cm. C. 2,5 cm. D. 1,1 cm.
Hng dn
Xt 2 12 12 1
tan tantan( )
1 tan tan
1 1
1 1
1 1 1 1.1 .
O Q O P
O Q O Pa aO Q O P O Q O P
aa a a
at cc ai khi 1 1. 6a O P O Q cm (BT C si).
Suy ra, PO2 = 7,5 cm v QO2 = 10 cm.
Tuyet pham cong pha Vat l GNTC tren kenh VTV2 Chu Van Bien
34
V P l cc tiu v Q l cc ai lin k nn:
7,5 4,5 0,5 2
10 8 1
k cm
k k
.
im Q l cc ai bc 1 vy N gn P nht l cc ai ng vi k = 2, ta c
2 2 2ON a ON 2,5ON cm PN = 2 cm Chn B.
Cu 6: (H - 2013): Trn mt ng thng c inh trong mi trng ng hng,
khng hp th m v phan xa m, mt my thu cch ngun m mt khoang d thu
c m c mc cng m l L; khi dich chuyn my thu ra xa ngun m thm 9 m
th mc cng m thu c l L 20 (dB). Khoang cch d l
A. 1 m. B. 9 m. C. 8 m. D. 10 m.
Hng dn
2 12 2
22 102
1 2
.10 10 104 9
L LL I rP dI Ir I r d
1d m Chn A.
Dao ng v sng in t
Cu 7: (H - 2013): Mach dao ng LC li tng ang hoat ng, in tch cc ai ca
t in l q0 = 10-6
C va cng dng in cc ai trong mach l I0 = 3 mA. Tnh t
thi im in tch trn t l q0, khoang thi gian ngn nht cng dng in
trong mach co ln bng I0 l
A. 10/3 ms. B. 1/6 s. C. 1/2 ms. D. 1/6 ms.
Hng dn
Tn s gc = I0/Q0 = 3000 rad/s, suy ra T = 2/ = 1/1500 s = 2/3 ms.
Thi gian ngn nht t lc q = q0 n i = I0 l T/4 = 1/6 ms Chn D.
Cu 8: (H - 2013): Song in t c tn s 10 MHz truyn trong chn khng vi bc
sng l
A. 3 m. B. 6 m. C. 60 m. D. 30 m.
Hng dn
30c
mf
Chn D.
Cu 9: (H - 2013): Mt mach dao ng LC l tng ang thc hin dao ng in t
t do. Bit in tch cc ai ca t in l q0 va cng dng in cc ai trong
mach l I0. Tai thi im cng dng in trong mach bng 0,5I0 th in tch ca t
in co ln:
A. 02
2
q. B. 0
3
2
q. C. 0
2
q. D. 0
5
2
q.
Cty TNHH MTV DVVH Khang Viet
35
Hng dn
Do i q nn:
2 2 2
2
0
0 0 0
31 0,5 1
2
i q qq q
I q q
Chn B.
Cu 10: (H - 2013): Hai mach dao ng in t l tng ang co dao ng in t t
do. in tch ca t in trong mach dao ng th nht v th hai ln lt l q1 v q2
vi 2 2 17
1 24 1,3.10q q , q tnh bng C. thi im t, in tch ca t in va cng
dng in trong mach dao ng th nht ln lt l 10-9
C va 6 mA, cng dng
in trong mach dao ng th hai co ln bng :
A. 10 mA. B. 6 mA. C. 4 mA. D. 8 mA.
Hng dn
T 2 2 17
1 24 1,3.10q q (1) ly ao hm theo thi gian ca hai v ta c:
1 1 2 2 1 1 2 28 ' 2 ' 0 8 2 0q q q q q i q i (2). T (1) v (2) thay cc gi tri q1 v i1 tnh
c i2 = 8 mA Chn D.
Cu 11: (H - 2013): Gia s mt v tinh dng trong truyn thng ang ng yn so vi
mt t mt cao xac inh trong mt phng Xich ao Trai t; ng thng ni v
tinh vi tm Trai t i qua kinh tuyn s 0. Coi Trai t nh mt qua cu, bn knh l
6370 km; khi lng l 6.1024
kg v chu k quay quanh trc ca n l 24 h; hng s hp
dn G = 6,67.10-11
N.m2/kg
2. Sng cc ngn f > 30 MHz pht t v tinh truyn thng n
cac im nm trn Xich ao Trai t trong khoang kinh nao di y:
A. T kinh 85020
n kinh 85
020
T.
B. T kinh 79020
n kinh 79
020
T.
C. T kinh 81020
n kinh 81
020
T.
D. T kinh 83020
T n kinh 83
020
.
Hng dn
Vi v tinh ia tnh (ng yn so vi Trai t), lc hp dn l lc hng tm nn:
2
2
2 GmMm r
T r
2
3
2
Tr GM
2
11 243
24.60.606,67.10 .6.10 42297523,87
2r m
Tuyet pham cong pha Vat l GNTC tren kenh VTV2 Chu Van Bien
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Vng ph sng nm trong min gia hai tip tuyn k t v tinh vi Trai t. T
o tinh c 0 '81 20
Rcos
r : T kinh 81020T n kinh 81020
Chn C.
Sng nh sng
Cu 12: (H - 2013): Trong chn khng, anh sang co bc sng ln nht trong s cc
anh sang o, vng, lam, tm l:
A. nh sng vng. B. nh sng tm. C. nh sng lam. D. anh sang o.
Hng dn
Bc sng giam theo th t : o > da cam > vng > lc > lam > chm > tm
Chn D.
Cu 13: (H 2013- cu nay a ra trong nm 2011): Trong th nghim Y ng v
giao thoa nh sng, nu thay nh sng n sc mu lam bng anh sang n sc mu
vng v gi nguyn cac iu kin khc th trn mn quan st:
A. Khoang vn tng ln. B. Khoang vn giam xung.
C. vi tri vn trung tm thay i. D. Khoang vn khng thay i.
Hng dn
V vng > lam nn v lam
v lam
D Di i
a a
Chn A.
Cu 14: (H - 2013): Khi ni v quang ph vach pht xa, pht biu nao sau y la sai?
A. Quang ph vach pht xa ca mt nguyn t l h thng nhng vach sng ring
l, ngn cach nhau bi nhng khoang ti.
B. Quang ph vach pht xa ca nguyn t ha hc khc nhau th khc nhau.
C. Quang ph vach pht xa do cht rn hoc cht long pht ra khi bi nung nng.
D. Trong quang ph vach pht xa ca nguyn t hidro, vng nh sng nhn thy
c bn vach c trng la: vach o, vach lam, vach chm, vach tm.
Hng dn
Quang ph vach pht xa do cht kh hoc hi co t khi nho pht ra khi bi nung
nng Chn C.
Cu 15: (H - 2013): Trong mt th nghim Y ng v giao thoa anh sang, bc sng nh
sang n sc l 600 nm, khoang cch gia hai khe hp l 1 mm, khoang cch t mt phng
cha hai khe n mn l 2 m. Khoang vn quan sat c trn mn c gi tri bng
A. 1,5 mm. B. 0,3 mm. C. 1,2 mm. D. 0,9 mm.
Hng dn
Khoang vn: 1,2D
i mma
Chn C.
Cu 16: (H - 2013): Thc hin th nghim Y ng v giao thoa vi anh sang co bc
sng . Khoang cch gia hai khe hp l 1 mm. Trn mn quan st, tai im M cch
vn trung tm 4,2 mm c vn sng bc 5. Gi c inh cac iu kin khc, di chuyn
dn mn quan st dc theo ng thng vung gc vi mt phng cha hai khe ra xa
Cty TNHH MTV DVVH Khang Viet
37
cho n khi vn giao thoa tai M chuyn thnh vn ti ln th hai th khoang dich mn
la 0,6 m. Bc sng bng:
A. 0,6 m. B. 0,5 m. C. 0,7 m. D. 0,4 m.
Hng dn
Vi tri im M: 35 5 4,2.10MD
x i ma
(1)
Ban u, cc vn ti tnh t vn trung tm n M ln lt c ta l 0,5i; 1,5i;
2,5i; 3,5i v 4,5i. Khi dich mn ra xa 0,6 m M tr thnh vn ti ln th 2 th xM = 3,5i
hay 3( 0,6)
3,5 4,2.10MD
x ma
(2)
T (1) v (2) tnh ra: D = 1,4 m, = 0,6 m Chn A.
Lng t nh sng
Cu 17: (H - 2013): Gii han quang in ca mt kim loai l 0,75 m . Cng thot
electron ra khoi kim loai bng:
A. 2,65.10-32
J. B. 26,5.10-32
J. C. 26,5.10-19
J. D. 2,65.10-19
J.
Hng dn
25
19
6
0
1,9875.102,65.10
0,75.10
hcA J
Cu 18 (H - 2013): Gi D la nng lng ca pho ton anh sang o, L la nng lng
ca pho ton nh sng lc, V la nng lng ca pho ton nh sng vng. Sp xp no sau
y ung:
A. V > L > D. B. L > V > D. C. L > D > V. D. D > V > L.
Hng dn
V o > vng > lc o < vng < lc Chn B.
Cu 19: (H - 2013): Gia s mt ngun sng ch phat ra anh sang n sc c tn s
7,5.1014
Hz. Cng sut pht xa ca ngun l 10 W. S photon m ngun pht ra trong
mt giy xp x bng:
A. 0,33.1020
. B. 0,33.1019
. C. 2,01.1019
. D. 2,01.1020
.
Hng dn
T cng thc: 192,01.10
PP N Nhf N
hf Chn C.
Cu 20: (H - 2013): Khi ni v photon pht biu nao di y ung:
A. Vi mi nh sang n sc c tn s xac inh, cac pho ton u mang nng lng
nh nhau.
B. Pho ton c th tn tai trong trang thai ng yn.
C. Nng lng ca pho ton cng ln khi bc sng nh sng ng vi pho ton o
cng ln.
D. Nng lng ca pho ton nh sng tm nho hn nng lng ca pho ton anh sang o.
Hng dn
Vi mi anh sang n sc c tn s xac inh, cac pho ton u mang nng lng
nh nhau = hf Chn A.
Tuyet pham cong pha Vat l GNTC tren kenh VTV2 Chu Van Bien
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Cu 21: (H - 2013): Bit bn knh Bo l r0 = 5,3.10-11
m. Bn knh qu ao dng M
trong nguyn t hidro l:
A. 132,5.10-11
m. B. 84,8.10-11
m. C. 21,2.10-11
m. D. 47,7.10-11
m.
Hng dn
Qu ao M ng vi n = 3 nn rM = 32r0 = 47,7.10
-11 m Chn D.
Cu 22: (H - 2013): Cc mc nng lng ca cc trang thi dng ca nguyn t
hidro c xac inh bng biu thc En = -13,6/n2 (eV) (n = 1, 2, 3). Nu nguyn t
hidro hp th mt photon co nng lng 2,55 eV th bc sng nho nht ca bc xa m
nguyn t hidro c th pht ra l:
A. 9,74.10-8
m. B. 1,46.10-8
m. C. 1,22.10-8
m. D. 4,87.10-8
m.
Hng dn
T En = -13,6/n2 (eV) suy ra: E1 = -13,6 (eV), E2 = -3,4 (eV), E3 = -68/45 (eV), E4 =
-0,85 (eV),...
Ta nhn thy: E4 E2 = 2,55 (eV), tc l nguyn t hidro mc E2 hp th mt
photon co nng lng 2,55 eV chuyn ln mc E4.
T mc E4 chuyn v mc E1 th pht ra bc xa co nng lng ln nht c th
(bc sng nho nht):
8min 414 1
9,74.10hc
mE E
Chn A.
Ht nhn nguyn t
Cu 23: (H - 2013): Hat nhn co ht khi cng ln th:
A. Nng lng lin kt ring cng nho. B. Nng lng lin kt cng ln.
C. Nng lng lin kt cng nho. D. Nng lng lin kt ring cng ln.
Hng dn
Nng lng lin kt t l thun vi ht khi: Wlk = mc2 Chn B.
Cu 24: (H - 2013): Cho khi lng ca hat proton, notron v hat tri 2
1 D ln lt
l: 1,0073u; 1,0087u v 2,0136u. Bit 1u = 931,5MeV/c2. Nng lng lin kt ca hat
nhn 2
1 D l:
A. 2,24 MeV. B. 3,06 MeV. C. 1,12 MeV. D. 4,48 MeV.
Hng dn
2.lk p n hnW Z m A Z m m c
1.1,0073 1.1,0087 2,0136 .931,5 2,24 MeV Chn A. Cu 25: (H - 2013): Tia nao sau y khng phai l tia phng xa:
A. Tia . B. Tia +. C. Tia . D. Tia X.
Hng dn
Tia X khng phai l tia phng xa Chn D.
Cu 26: (H - 2013): Ban u mt mu cht phng xa nguyn cht c N0 hat nhn.
Bit chu k bn r ca cht phng xa ny l T. Sau thi gian 4T, k t thi im ban
u, s hat nhn cha phn ra ca mu cht phng xa ny l
A. 15N0/16. B. N0/16. C. N0/4. D. N0/8.
Cty TNHH MTV DVVH Khang Viet
39
Hng dn
S hat nhn cn lai tnh theo: 0 0 0/ 42 2 16t T
N N NN Chn B.
Cu 27: (H - 2013): Mt hat c khi lng ngh m0. Theo thuyt tng i, khi
lng ng (khi lng tng i tnh) ca hat ny khi chuyn ng vi tc 0,6c
(c l tc nh sng trong chn khng) l:
A. 1,75m0. B. 1,25m0. C. 0,36m0. D. 0,25m0.
Hng dn
p dng: 00
2
2
1,25
1
mm m
v
c
Chn B.
Cu 28: (H - 2013): Hin nay urani t nhin cha hai ng vi phng xa 235
U v 238
U, vi t l s hat 235
U v s hat 238
U l 7/1000. Bit chu k bn r ca 235
U v 238
U
ln lt l 7,00.108 nm va 4,50.10
9 nm. Cach y bao nhiu nm, urani t nhin c t
l s hat 235
U v s hat 238
U l 3/100?
A. 2,74 t nm. B. 1,74 t nm. C. 2,22 t nm. D. 3,15 t nm.
Hng dn
S hat U235 v U238 cn lai hin nay ln lt: 1
1
ln 2
1 01
ln 2
1 01
tT
tT
N N e
N N e
2 11 1 1 1
ln 2 ln 24,5 0,7011
2 02
7 3
1000 100
t tT TNN
e eN N
t = 1,74 (t nm) Chn B.
Cu 29: (H - 2013): Dng mt hat co ng nng 7,7 MeV bn vo hat nhn 14
7 N ang ng yn gy ra phan ng 14 1 17
7 1 8N p O . Hat proton bay ra theo
phng vung goc vi phng bay ti ca hat . Cho khi lng cc hat nhn
14 174,0015 ; 1,0073 ; 13,9992 ; 16,9947p N om u m u m u m u . Bit 1u = 931,5
(MeV/c2). ng nng ca hat
17
8 O l:
A.6,145 MeV. B. 2,214 MeV. C. 1,345 MeV. D. 2,075 MeV.
Hng dn
Tnh 2 1,211t sE m m c MeV
Theo bi ton pv v
nn ta c h:
p p O O
p O
m W m W m W
E W W W
1,0073 4,0015.7,7 16,9947
1,211 7,7
p O
p O
W W
W W
4,414
2,075
p
O
W MeV
W MeV
Chn D.
Tuyet pham cong pha Vat l GNTC tren kenh VTV2 Chu Van Bien
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Kinh nghim gii nhanh: A B C D
* Nu C Dv v
th C C D D A Am W m W m W
* Nu C Av v
th C C A A D Dm W m W m W
Sau o, kt hp vi C D AE W W W . Vi mi bi ton c th, phai xac inh r
u la hat A, hat B, hat C v hat D.
Cu 30: (H - 2013): Mt l phan ng phn hach c cng sut 200 MW. Cho rng
ton b nng lng m l phan ng nay sinh ra u do s phn hach ca 235
U va ng
vi ny ch bi tiu hao bi qu trnh phn hach. Coi mi nm co 365 ngay; mi phn
hach sinh ra 200 MeV; s Avgaro NA = 6,02.1023
mol-1
. Khi lng 235
U m l phan
ng tiu th trong 3 nm la:
A. 461,6 g. B. 461,6 kg. C. 230,8 kg. D. 230,8 g.
Hng dn
Nng lng do phn hach sinh ra trong 3 nm:
Atp = Aich = Pich.t = 200.106.3.365.86400 = 1,89216.10
16 (J).
V mi phn hach toa E = 200 MeV = 3,2.10-11
(J) nn s hat U235 cn phn hach l:
265,913.10
tpAN
E
Khi lng U235 tng ng: 26
23
5,913.100,235 230,8
6,02.10A
Nm A kg
N Chn C.
5. NM 2014
Sng c hc (7 cu 3 d)
Cu 1: (H-2014) Mt song c truyn trn mt si dy rt di vi tc 1 m/s v chu
k 0,5 s. Song c nay co bc sng l
A. 150 cm. B. 100 cm. C. 50 cm. D. 25 cm.
Hng dn
= vT = 0,5 (m/s) Chn C.
Cu 2: (H-2014) Trong mt th nghim giao thoa song nc, hai ngun S1 v S2 cch
nhau 16 cm, dao ng theo phng vung goc vi mt nc, cung bin , cng pha,
cng tn s 80 Hz. Tc truyn sng trn mt nc l 40 cm/s. mt nc, gi d l
ng trung trc ca oan S1S2. Trn d, im M cch S1 10 cm; im N dao ng cng
pha vi M v gn M nht s cch M mt oan c gi tri gn gi tr no nht sau y?
A. 7,8 mm. B. 6,8 mm. C. 9,8 mm. D. 8,8 mm.
Hng dn
Cty TNHH MTV DVVH Khang Viet
41
2 210 8 6 0,8 8MN ON OM cm mm Chn A.
Cu 3: (H-2014) c lng su ca mt ging can nc, mt ngi dng
ng h bm giy, gh st tai vo ming ging v tha mt hn a ri t do t ming
ging; sau 3 s th ngi o nghe thy ting hn a p vao ay ging. Gia s tc
truyn m trong khng kh l 330 m/s, ly g = 9,9 m/s2. su c lng ca ging l
A. 43 m. B. 45 m. C. 39 m. D. 41 m.
Hng dn
2
11
2
2 2
2 9,9
300
gt h hh t
g
h ht
v
Thi gian vt ri :
Thi gian m truyn t y n tai ngi :
1 2 32
3 419,9 330
t t h hh m
Chn D.
Cu 4: (H-2014) Mt song c truyn dc theo mt si dy an hi rt di vi bin
6 mm. Tai mt thi im, hai phn t trn dy cng lch khoi vi tr cn bng 3 mm,
chuyn ng ngc chiu v cch nhau mt khoang ngn nht l 8 cm (tnh theo
phng truyn sng). Gi l t s ca tc dao ng cc ai ca mt phn t trn
dy vi tc truyn sng. gn gi tr no nht sau y?
A. 0,105. B. 0,179. C. 0,079. D. 0,314.
Hng dn
Hai phn t gn nhau nht co ln li A/2 chuyn ng ngc chiu nhau cch
nhau d = /3 = 8 cm = 24 cm. Tc truyn sng trn dy v tc dao ng cc
ai ca phn t trn dy ln lt l :
v = max
max
20,157
2
vv AT
vv A A
T
Chn B.
Cu 5: (H-2014) Trong m nhac, khoang cch gia hai nt nhac trong mt qung
c tnh bng cung v na cung (nc). Mi qung tm c chia thnh 12 nc. Hai nt
nhac cch nhau na cung th hai m (cao, thp) tng ng vi hai nt nhac ny c tn
s thoa mn 12 12
c tf 2f . Tp hp tt ca cc m trong mt qung tm gi l mt gam
(m giai). Xt mt gam vi khoang cch t nt n cc nt tip theo R, Mi, Fa,
Sol, La, Si, tng ng l 2 nc, 4 nc, 5 nc, 7 nc , 9 nc, 11 nc, 12 nc. Trong gam ny,
nu m ng vi nt La c tn s 440 Hz th m ng vi nt Sol c tn s l
A. 330 Hz. B. 392 Hz. C. 494 Hz. D. 415 Hz.
Tuyet pham cong pha Vat l GNTC tren kenh VTV2 Chu Van Bien
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Hng dn
T nt La n nt Sol cch nhau 2nc nn 12 122.2La Solf f
12 12440 2.2 391,995Sol Solf f Hz Chn B.
Cu 6: (H-2014) Trn mt si dy an hi ang co song dng n inh vi khoang
cch gia hai nt sng lin tip l 6 cm. Trn dy c nhng phn t song dao ng vi
tn s 5 Hz va bin ln nht l 3 cm. Gi N l vi tr ca mt nt sng; C v D l hai
phn t trn dy hai bn ca N v c vi tr cn bng cch N ln lt l 10,5 cm v 7
cm. Tai thi im t1, phn t C co li 1,5 cm va ang hng v vi tr cn bng. Vo
thi im 2 179
40t t s , phn t D co li l
A. -0,75 cm. B. 1,50 cm. C. -1,50 cm. D. 0,75 cm.
Hng dn
Theo bi ra: 6 122
cm cm
Biu thc sng dng: max2 2
sin cos 3sin cos1012
x xu A t t cm
2 . 10,5 3 23sin cos10 cos10
12 2
2 .73sin cos10 1,5cos10
12
C
D
u t t cm
u t t cm
1
1
11,5; 0
79
401
3 2cos10 10
2 4
791,5cos10 1,5cos10 1,5
40
C C
t t
C u v
t t
D D
u t cm t
u t cm u t cm
Chn C.
Cu 7: (H-2014) Trong mi trng ng hng v khng hp th m, co 3 im
thng hang theo ung th t A; B; C vi AB = 100 m, AC = 250 m. Khi t tai A mt
ngun im pht m cng sut P th mc cng m tai B l 100 dB. Bo ngun m
tai A, t tai B mt ngun im pht m cng sut 2P th mc cng m tai A v C l
A. 103 dB v 99,5 dB.
B. 100 dB v 96,5 dB.
C. 103 dB v 96,5 dB.
D. 100 dB v 99,5 dB.
Hng dn
R Mi Fa Sol La Si
Cty TNHH MTV DVVH Khang Viet
43
p dng: 02 .104
LPI Ir
* Khi t ngun m P tai A: 10
02.10
4 .100
PI
(1)
* Khi t ngun m 2P tai B: 02
02
2.10
4 .100
2.10
4 .150
A
C
L
L
PI
PI
(2)
T (1), (2):
10
10
2
2 10 10,3
210 9,95
1,5
A
C
L
A
L
C
L B
L B
Chn A.
Dao ng v sng in t (4 cu 3 d)
Cu 8: (H - 2014) Trong mach dao ng LC l tng ang co dao ng in t t do,
in tch ca mt ban t in va cng dng in qua cun cam thun bin thin
iu ha theo thi gian
A. lun ngc pha nhau.
B. lun cng pha nhau.
C. vi cung bin .
D. vi cng tn s.
Hng dn
in tch ca mt ban t in va cng dng in qua cun cam thun bin
thin iu ha theo thi gian vi cng tn s Chn D.
Cu 9: (H - 2014) Mt mach dao ng LC li tng ang co dao ng in t t do
vi in tch cc ai ca t in l Q0 va cng dng in cc ai trong mach l I0.
Dao ng in t t do trong mach c chu k l
A. 0
0
4 QT
I
. B. 0
0
QT
2I
. C. 0
0
2 QT
I
. D. 0
0
3 QT
I
.
Hng dn
2 2 220 0 0 0
2
0 0
22 2
T LCQ LI Q QW LC TC I I
Chn C.
Cu 10: (H - 2014) Mt t in co in dung C tich in Q0. Nu ni t in vi
cun cam thun co t cam L1 hoc vi cun cam thun co t cam L2 th trong
mach co dao ng in t t do vi cng dng in cc ai l 20mA hoc 10 mA.
Nu ni t in vi cun cam thun co t cam L3 = (9L1+4L2) th trong mach c dao
ng in t t do vi cng dng in cc ai l
A. 9 mA. B. 4 mA. C. 10 mA. D. 5 mA.
Tuyet pham cong pha Vat l GNTC tren kenh VTV2 Chu Van Bien
44
Hng dn
3 1 22 2 2 2 2 2
9 40 0 0 0 0 0032 2 2 2
0 03 01 02
9 4 42 2
L L LQ LI Q Q Q QW L I mA
C I C I I I
Cu 11: (H - 2014) Hai mach dao
ng in t LC li tng ang co
dao ng in t t do vi cc
cng dng in tc thi trong
hai mach l i1 v i2 c biu din
nh hnh v. Tng in tch ca hai
t in trong hai mach cng mt thi im c gi tri ln nht bng
A. 4
C
B. 3
C
C. 5
C
D. 10
C
Hng dn
1 1
2 2
0,0080,008cos 2000 cos2000
2 2000
0,0060,006cos 2000 cos 2000
2000 2
i t A q t C
i t A q t C
1 2q q q
2 20 01 025
Q Q Q C
Chn C.
Tnh cht sng nh sng (7 cu - 7 d)
Cu 12: (H - 2014) Tia X
A. mang in tch m nn bi lch trong in trng.
B. cng ban cht vi sng m
C. c tn s nho hn tn s ca tia hng ngoai
D. cng ban cht vi tia t ngoai
Hng dn
Tia X cng ban cht vi tia t ngoai l ban cht sng in t Chn D.
Cu 13: (H - 2014) Hin tng chm nh sng trng i qua lng kinh, bi phn tch
thanh cac chum sang n sc l hin tng
A. phan xa ton phn. B. phan xa nh sng.
C. tn sc nh sng. D. giao thoa nh sng.
Hng dn
Hin tng chm nh sng trng i qua lng kinh, bi phn tch thnh cc chm
sang n sc l hin tng tn sc nh sng Chn C.
Cu 14: (H - 2014) Gi n, nt v nv ln lt l chit sut ca mt mi trng trong
sut i vi cac anh sang n sc o, tm v vng. Sp xp nao sau y la ung?
A. n< nv< nt B. nv >n> nt C. n >nt> nv D. nt >n> nv
Cty TNHH MTV DVVH Khang Viet
45
Hng dn
Chit sut tng theo th t n < ndc < nv < nlc < nlam < nchm < nt Chn A.
Cu 15: (H - 2014) Trong th nghim Y-ng v giao thoa nh sng, khoang cch gia
hai khe l 1 mm, khoang cch t mt phng cha hai khe n mn quan st l 2 m.
Ngun sang n sc co bc sng 0,45 m . Khoang vn giao thoa trn mn bng
A. 0,2 mm. B. 0,9 mm. C. 0,5 mm. D. 0,6 mm.
Hng dn
0,9D
i mma
Chn B.
Cu 16: (H - 2014) Trong chn khng, cc bc xa co bc song tng dn theo th t
ung la
A. nh sng nhn thy; tia t ngoai; tia X; tia gamma; sng v tuyn v tia hng ngoai.
B. sng v tuyn; tia hng ngoai; nh sng nhn thy; tia t ngoai; tia X v tia gamma.
C. tia gamma; tia X; tia t ngoai; nh sng nhn thy; tia hng ngoai v sng v tuyn.
D. tia hng ngoai; nh sng nhn thy; tia t ngoai; tia X; tia gamma v sng v tuyn.
Hng dn
Trong chn khng, cc bc xa co bc song tng dn theo th t ung la tia
gamma; tia X; tia t ngoai; nh sng nhn thy; tia hng ngoai v sng v tuyn
Chn C.
Cu 17: (H - 2014) Trong chn khng, bc sng nh sng lc bng
A. 546 mm. B. 546 m. C. 546 pm. D. 546 nm.
Hng dn
Trong chn khng, bc sng nh sng lc bng 546 nm Chn D.
Cu 18: (H - 2014) Khi ni v tia hng ngoai v tia t ngoai, pht biu nao sau y
ung?
A. Tia hng ngoai v tia t ngoai gy ra hin tng quang in i vi mi kim loai.
B. Tn s ca tia hng ngoai nho hn tn s ca tia t ngoai.
C. Tia hng ngoai v tia t ngoai u lm ion ha manh cc cht kh.
D. Mt vt bi nung nng pht ra tia t ngoai, khi o vt khng pht ra tia hng ngoai.
Hng dn
Tn s ca tia hng ngoai nho hn tn s ca tia t ngoai Chn B.
Tnh cht ht ca nh sng (4 cu 4 d)
Cu 19: (H - 2014) Theo mu Bo v nguyn t hir, nu lc tng tac tnh in
gia lectron v hat nhn khi lectron chuyn ng trn qu ao dng L l F th khi
lectron chuyn ng trn qu ao dng N, lc ny s l
A.F
16. B.
F
9. C.
F
4. D.
F
25.
Tuyet pham cong pha Vat l GNTC tren kenh VTV2 Chu Van Bien
46
Hng dn
4 42 2
2 4 2
0
' 2 1
' 4 16CL
n
e e F nF k k
r n r F n
Chn A.
Cu 20: (H - 2014) Trong chn khng, mt anh sang co bc sng l 0,60 m. Nng
lng ca phtn nh sng ny bng
A. 4,07 eV. B. 5,14 eV. C. 3,34 eV. D. 2,07 eV.
Hng dn
26
6 19
19,875.10 1. 2,07
0,6.10 1,6.10
hc eVeV
Chn D.
Cu 21: (H - 2014) Cng thot lectron ca mt kim loai l 4,14 eV. Gii han quang
in ca kim loai ny l
A. 0,6 m. B. 0,3 m. C. 0,4 m. D. 0,2 m.
Hng dn
26
0 19
19,875.100,3
4,14.1,6.10
hcm
A
Chn B.
Cu 22: (H - 2014) Chm nh sng laze khng c ng dng
A. trong truyn tin bng cp quang. B. lm dao m trong y hc.
C. lm ngun pht siu m. D. trong u c a CD.
Hng dn
Chm nh sng laze khng c ng dng lm ngun pht siu m
Chn C.
Ht nhn nguyn t (6 cu 5 d)
Cu 23: (H - 2014) S nucln ca hat nhn 230
90 Th nhiu hn s nucln ca hat
nhn210
84 Po l
A. 6. B. 126. C. 20. D. 14.
Hng dn
S nucln ca hat nhn 230
90 Th l 230 v nucln ca hat nhn210
84 Po l 210
Chn C.
Cu 24: (H - 2014) ng vi l nhng nguyn t m hat nhn c cng s
A. prtn nhng khac s nucln. B. nucln nhng khac s ntron.
C. nucln nhng khac s prtn. D. ntron nhng khac s prtn.
Hng dn
ng vi l nhng nguyn t m hat nhn c cng s prtn nhng khac s nucln
Chn A.
Cu 25: (H - 2014) Trong cc hat nhn nguyn t: 4 56 238
2 26 92; ;He Fe U v 230
90Th , hat
nhn bn vng nht l
Cty TNHH MTV DVVH Khang Viet
47
A. 4
2 He . B. 230
90Th . C. 56
26 Fe . D. 238
92U .
Hng dn
Hat nhn trung bnh l bn vng nht ri n hat nhn nng v km bn nht l hat
nhn nh Chn C.
Cu 26: (H - 2014) Tia
A. c vn tc bng vn tc nh sng trong chn khng.
B. l dng cc hat nhn 4
2 He .
C. khng bi lch khi i qua in trng v t trng.
D. l dng cc hat nhn nguyn t hir.
Hng dn
Tia l dng cc hat nhn 4
2 He Chn B.
Cu 27: (H - 2014) Trong phan ng hat nhn khng c s bao ton
A. nng lng ton phn. B. s nucln.
C. ng lng. D. s ntron.
Hng dn
Trong phan ng hat nhn khng c s bao ton s ntron Chn D.
Cu 28: (H - 2014) Bn hat vo hat nhn nguyn t nhm ang ng yn gy ra
phan ng: 4 27 30 1
2 13 15 0He Al P n . Bit phan ng thu nng lng l 2,70 MeV; gia
s hai hat tao thnh bay ra vi cng vn tc v phan ng khng km bc xa . Ly
khi lng ca cc hat tinh theo n vi u c gi tri bng s khi ca chung. ng nng
ca hat l
A. 2,70 MeV. B. 3,10 MeV. C. 1,35 MeV. D.1,55 MeV.
Hng dn
P nv v v
P P n n
P n
m vm v m v m v v
m m
2
2
2
2
120
2 961
4
2 961
PPP
P n
n nn
P n
m m W WmW v
m m
m m m W WW v
m m
Mt khc:
120 4
2,7 3,1961 961
P n
W WE W W W W W MeV Chn B.
Tuyet pham cong pha Vat l GNTC tren kenh VTV2 Chu Van Bien
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Chu e 1. HIEN TNG SONG C HOC
1. BI TON LIN QUAN N S TRUYN SNG
Dng 1. BI TON LIN QUAN N S TRUYN SNG
Phng php gii
Bc sng:
2v
vT vf
.
Khi sng lan truyn th
sn trc i ln v sn
sau i xung. Xt nhng
im nm trn cng mt
phng truyn sng th
khong cch gia 2 im
dao ng :
*cng pha l l k (k l s nguyn) min
l
*ngc pha l 2 12
l k
(k l s nguyn) min
0,5l
*vung pha l 2 14
l k
(k l s nguyn) min
0, 25l
V d 1: Trong mi trng n hi c mt sng c c tn s 10 Hz, tc truyn
sng l 40 cm/s. Hai im M v N trn phng truyn sng dao ng cng pha nhau,
gia chng ch c 2 im khc dao ng ngc pha vi M. Khong cch MN l
A. 8,75 cm. B. 10,50 cm. C. 8,00 cm. D. 12,25 cm.
Hng dn
Hai im M, N dao ng cng pha nn: MN = ; 2; 3 Nhng gia chng ch
c 2 im dao ng ngc pha vi M nn bt buc: MN = 2
hay 40
2 2 2. 810
vMN cm
f Chn C.
V d 2: Trong mi trng n hi c mt sng c c tn s 50 Hz, tc truyn
sng l 175 cm/s. Hai im M v N trn phng truyn sng dao ng ngc pha nhau,
gia chng ch c 2 im khc cng dao ng ngc pha vi M. Khong cch MN l:
A. 8,75 cm. B. 10,5 cm. C. 7,0 cm. D. 12,25 cm.
Hng dn
Hai im M, N dao ng ngc pha nn: MN = 0,5; 1,5; 2,5 Nhng gia
chng ch c 2 im khc dao ng ngc pha vi M nn bt buc: MN = 2,5 hay
2,5 2,5 8,75v
MN cmf
Chn A.
Cty TNHH MTV DVVH Khang Viet
49
V d 3: Trong mi trng n hi c mt sng c c tn s 10 Hz, tc truyn
sng l 40 cm/s. Hai im M v N trn phng truyn sng dao ng cng pha nhau,
gia chng ch c 2 im E v F. Bit rng, khi E hoc F c tc dao ng cc i th
ti M tc dao ng cc tiu. Khong cch MN l:
A. 4,0 cm. B. 6,0 cm. C. 8,0 cm. D. 4,5 cm.
Hng dn
Theo bi ra, khi E hoc F c tc dao ng cc i th ti M tc dao ng cc
tiu, ngha l E, F dao ng vung pha vi M.
Hai im M, N dao ng cng pha nn: MN = ; 2; 3 Nhng gia chng ch
c 2 im dao ng vung pha vi M nn bt buc: MN = hay
4v
MN cmf
AChn .
V d 4: Hai im A, B cng phng truyn sng, cch nhau 24 cm. Trn on AB c 3
im A1, A2, A3 dao ng cng pha vi A, v ba im B1, B2, B3 dao ng cng pha vi B.
Sng truyn theo th t A, B1, A1, B2, A2, B3, A3, B v A3B = 3 cm. Tm bc sng.
A. 7,0 cm. B. 7,0 cm. C. 3,0 cm. D. 9,0 cm.
Hng dn
33 24 3 3 7AB A B cm BChn .
V d 5: Mt sng ngang truyn trn mt si dy rt di. Hai im PQ = 5/4 sng
truyn t P n Q. Kt Lun no sau y ng.
A. Khi Q c li cc i th P c vn tc cc i.
B. Li P, Q lun tri du.
C. Khi P c li cc i th Q c vn tc cc tiu.
D. Khi P c th nng cc i th Q c th nng cc tiu.
Hng dn
Tuyet pham cong pha Vat l GNTC tren kenh VTV2 Chu Van Bien
50
Khi P c th nng cc i (P v tr cao nht hoc thp nht) th Q qua v tr cn
bng nn th nng cc tiu Chn D.
Ch : Da vo th sng hnh sin c th xc nh c hng truyn sng:
*Nu sng truyn A n B th on EB ang i ln (DE i xung, CD i ln v AC i
xung).
*Nu sng truyn B n A th on AC ang i ln (CD i xung, DE i ln v EB i
xung).
V d 6: Mt sng ngang truyn trn mt nc c tn s 10 Hz
ti mt thi im no mt phn mt nc c dng nh hnh
v. Trong khong cch t