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LUYN THI I HC VT L 2014 Thy Lm Phong

Gieo hnh vi gt thi quen. Gieo thi quen gt tnh cch. Gieo tnh cch gt s phn. ( Dick Lyles) 1

TNG HP CC CNG THC C BN V CNG THC GII NHANHVT L 12 - LUYN THI I HC 2014

CHNG V: SNG NH SNG (6 cu)Bi 1: Tn Sc nh Sng.

Th nghim ca Newton:_ nh sng mi trng i qua lng knh th b tch ra thnhNhiu mu sc khc nhau trong lch t nht l mu vNhiu nht l mu tm.

nh ngha hin tng tn sc nh sng:+ L hin tng phn tch chm nh sng phc tp thnh ccthnhphn n sc khc nhau.+ y cng l min ca nh sng nhn thy(nh sng kh kin)

C bc sng t 0,38 m 0,76 m.Gii thch hin tng:+ Theo thuyt sng nh sng, th bin sngv bc sngl hai

i lng t l nghch ( E =hc

=

1

2KA

2).

+ Trong mi trng chn khng hay khng khdo cc mu sc c cng tc c = 3.108 m/s, cc mu sc chngcht ln nhau to thnh mu trng.

+ Khi trong mi trng mi(v d: lng knh) th c s va chm gia cc phn t mi trng vi cc phn t musc, mu c A min nn va chm t v mu tm th ngc li.

+ Nguyn nhn ca hin tng trn chnh l do chit sut gia hai mi trng hay t s gia vn tc gia

hai mi trng. ( n =

c

v > 1, v

max n

min, v

tm min n

tm max) Chit sut tng t n tm, chit sutph thuc vo bn cht ca mi trng v tn s ca nh sng ti. (n n

t, n {MT,f})

Cc khi nim mi:+ nh sng n sc: l nh sng khng b tn sc khi i qua lng knh. Mi nh sng n sc c mt mu gi l

mu n sc. Mi mu n sc trong mi mi trng c mt bc sng xc nh.+ nh sng trngl tp hp ca v s nh sng n sc khc nhau c mu bin thin lin tc t n tm.+ Di c mu nh cu vng(c v s mu nhng c chia thnh 7 mu chnh l , cam, vng, lc, lam, chm, tm)

gi l quang ph ca nh sng trng.Khi truyn qua cc mi trng trong sut khc nhau vn tc ca nh sng thay i, bc sng ca nh sng thay icn tn s ca nh sng th khng thay i.ng dng ca hin tng tn sc nh sng:

+ Dng lm my quang ph (Dng lng knh trn to ra h tn sc -Xem bi 2 hiu r hn )+ Gii thch hin tng cu vng ?(Cu vngl hin tngtn scca ccnh sng tMt Trikhikhc xvphn xqua cc gitncma)Nhc li mt s cng thc v Lng knh(Lp 11):

+ Cng thc tng qut:

sini1 = n.sinr1sini2 = n.sinr2A = r1 + r2D = i1 + i2A

Trong :

i l gc tir l gc khc x

A l gc chitquangD l gc lchgiagc tiv gc khc x

+ Trng hp iv A nh(i, A < 10o)

i1 = n.r1i2 = nr2A = r1+ r

2

D = (n1)A
http://vi.wikipedia.org/w/index.php?title=T%C3%A1n_s%E1%BA%AFc&action=edit&redlink=1http://vi.wikipedia.org/w/index.php?title=T%C3%A1n_s%E1%BA%AFc&action=edit&redlink=1http://vi.wikipedia.org/wiki/%C3%81nh_s%C3%A1nghttp://vi.wikipedia.org/wiki/%C3%81nh_s%C3%A1nghttp://vi.wikipedia.org/wiki/M%E1%BA%B7t_Tr%E1%BB%9Dihttp://vi.wikipedia.org/wiki/M%E1%BA%B7t_Tr%E1%BB%9Dihttp://vi.wikipedia.org/wiki/Kh%C3%BAc_x%E1%BA%A1http://vi.wikipedia.org/wiki/Kh%C3%BAc_x%E1%BA%A1http://vi.wikipedia.org/wiki/Kh%C3%BAc_x%E1%BA%A1http://vi.wikipedia.org/wiki/Ph%E1%BA%A3n_x%E1%BA%A1http://vi.wikipedia.org/wiki/Ph%E1%BA%A3n_x%E1%BA%A1http://vi.wikipedia.org/wiki/N%C6%B0%E1%BB%9Bchttp://vi.wikipedia.org/wiki/M%C6%B0ahttp://vi.wikipedia.org/wiki/M%C6%B0ahttp://vi.wikipedia.org/wiki/M%C6%B0ahttp://vi.wikipedia.org/wiki/M%C6%B0ahttp://vi.wikipedia.org/wiki/N%C6%B0%E1%BB%9Bchttp://vi.wikipedia.org/wiki/Ph%E1%BA%A3n_x%E1%BA%A1http://vi.wikipedia.org/wiki/Kh%C3%BAc_x%E1%BA%A1http://vi.wikipedia.org/wiki/M%E1%BA%B7t_Tr%E1%BB%9Dihttp://vi.wikipedia.org/wiki/%C3%81nh_s%C3%A1nghttp://vi.wikipedia.org/w/index.php?title=T%C3%A1n_s%E1%BA%AFc&action=edit&redlink=1

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+ Nu Gc lch cc tiu D min

i1= i2

r1= r

2=

A2

D min= 2i - A

(Khi tia l song song vi mt y lng knh A = 2r)

+ Cng thc tnh gc lch cc tiu: sinD min+ A

2= n.sin

A2

+ iu kin c "phn x ton phn": n 1> n2, i i

giihnvi sin i

gh=

n 2n 1

+ Vi nh sng trng: n

n

n

tm

tm

Bi 2: My Quang Ph V Cc Loi Quang Ph.My quang ph: l dng c phn tch chm sng a sc thnh n sc khc nhau da trn hin tng Tn sc

nh sng.

Cu to: Gm c ba b phn chnh

+ ng chun trc: l b phn to ra chm sng song song.+ H tn sc: l lng knh dng phn tch chm sng song song t tm.+ Bung nh: dng quan st hay chp nh quang ph.

Cc loi my quang ph:

Quang ph lin tc Quang ph vch pht x Quang ph vch hp th

nh ngha Gm mt di mu bin thinlin tc t n tm..

Gm cc vch mu ring l,ngn cch nhau bi nhngkhong ti hay vch mu trnnn ti

L quang ph lin tc thiu mt svch mu do cht kh hay hi hpth hay vch ti trn nn QPLT.

Ngun pht Do cc cht rn, cht lnghay cht kh c p sut lnkhi b nung nngpht ra

Do cc cht kh hay hi psut thp khi b kch thchbngin hay nhitpht ra.

-Nhi t cu a chngphi thp hnnhi t ngun pha t quang phlintc. to hpthu< t

o ngunpht

c im Khng ph thuc thnh phncu to ngun sng.

Ch ph thuc nhit cangun sng.

Cc nguyn t khc nhau thkhc nhau v: s lng vch,mu sc, bc sng (v tr

vch), cng sng.- Mi nguyn t ho hc c mtquang ph vch c trng canguyn t .

- Quang ph hp thu ca cht kh chcha cc vch hp th.

- Cn quang ph ca cht lng v rn

li cha cc m, mi m gmnhiu vch hp th ni tip nhaumt cch lin tc .

ng dng Dng xc nh nhit ca cc vt rt xa nh MtTri, Ngi Sao,...

Tm nguyn t v hm lngnguyn t.

Nhn bit c s co m t cuanguyn t trong ca c h n h p hayh p cht.

Hin tng o vch: l hin tng QP vch pht x QP vch hp th.nh lut Kirehhoff:Nguyn t ch pht x mu m n hp th v ngcli.Phn tch quang ph: l phng php Vt L dng xc nh "thnh phn ha hc" ca cht bng cch phn

tch QP ca cht .(phn tch nh tnh tm nguyn t, phn tch nh lng tm hm lng) vi u im: "tuyti t xa", kt qu nhanh, xc nh nhiu cht, rt nhy vi hm lng nh.

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Bi 3: Giao Thoa nh Sng - Vn Trng Vn.Nhc li nhiu x nh sng: l hin tng truyn sai lch vi s truyn thng ca nh sng khi i qua l nhhoc gp vt cn. Hin tng nhiu x nh sng chng t nh sng c tnh cht sng.Hin tng Giao thoa nh sng:

Th nghimY- ng (Young)_ Hai ngun S 1v S

2l hai ngun kt hp c cng tn s f

v lch pha khng i theo thi gian._ Sng nh sng pht ra t hai ngun gi l hai nh sngkt hp._ Trong vng giao thoa, xut hin cc vn sng (do haisng cng pha gp nhau), cc vn ti(do hai sng ngc

pha gp nhau) v nm xen k, cch ugi l hin tnggiao thoa nh sng.

_ Hin tng giao thoa nh sng l bng chng thcnghim nh sng c bn cht sng.

Cc khi nim mi trong giao thoa nh sng:(t S 1S 2 = a)_ Hiu quang trnh: t = d 2- d

1

S 1HA: d12 = D

2 + S

1H

2

S 2HA: d22 = D

2 + S

2H

2

Vy d 22 - d

12 = S

2H

2 - S

1H

2

(d 2- d1)(d

2+ d

1) = S

2H

2 - S

1H

2

=S 2H

2 - S

1H

2

d1+ d

2

= (S1S 2+ S 1H)2 - S 1H2

d1+ d

2

=2S

1S

2(S

1H +

S1S

2

2)

d1+ d

2

=2ax

d 1+ d2

DoD >>>> a d 1d2D =

axD

_ V tr ca cc vn giao thoa:Gi s ngun S 1v S

2c phng trnh l u

S1= u

S2= acost. (Xem k li phn giao thoa sng c).

Theo hnh trn, A l mt im nm trong vng giao thoa v nhn giao thoa ca hai ngun sng S 1v S2.

Vy

u

AS1= acos(t -2d 1 )

u

AS2= acos(t -2d 2

)

u A= u

AS1+ u

AS2= 2acos(d

1- d

2)

.cos

t - (d

1+ d

2)

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Do nu ti Acho vn sng(cng pha vi hai ngun) (d 1+ d

2)

= k2

d 1= k= kax

D= kx = k

Da

(k Z)

Nu ti Acho vn ti(ngc pha vi hai ngun) (d 1+ d

2)

= (2k + 1)

d 1= (2k + 1)2

= (2k + 1)2

x = (k + 0,5)Da

(k Z)

_ Khong vn i(m): l khong cch gia hai vn sng (vn ti) lin tip. i = Da

= aiD

Gia n vn sng (vn ti) lin tip c (n 1) khong vn._ Ch v n v:

+ Hiu quang trnh: =axD, trong

a(mm) l khongcch giahai khe

x(mm) l vtr ca1 imtrn mnD(m) l khongcch thai khe nmn

+ Khong vn: i =Da

, trong i(mm) l khongvn(m) lbcsng nh sng

k = -2 k = -1 k = 0 k = 1 k = 2 (Vn ti)

Hnh nh vn giao thoa

Vn sng trung tm

k = -2 k = -1 k = 0 k = 1 k = 2

V tr vn sng bc (th) n: |x| = ki(vi k = n Z )

V tr vn ti th n: |x| = (k + 0,5)i(vi k = n - 1 bnphik = -n bn tri

k Z)

ng dng ca hin tng giao thoa nh sng:

+Nh chng ta bit, khong vn i =

Da =

ai

D

+ a v D l hai gi tr khng i khi thc hin th nghim giao thoa nh sng. Khongvn i ta hon ton c tho c trn mn E. V vy d dng tnh c bc sng o bc sng nh sng.Vn trng vn: (gii thch k phn bi tp)+Nu ch dng n sc cho th nghim trn th chng ta hon ton ch nhn thy cc v n sng v vn ti ca mt

loi bc x .+Nu dng t 2 bc sng tr ln th bt u c hin tng "vn trng vn" xy ra.+ Trng hp c bit nu thc hin giao thoa vi "nh sng trng"th ti VSTT c mu trng, hai bn vn trung

tm l cc di mu cu vng gi l quang ph lin tc. Chiu di ca QPLT ng vi bc giao thoa. ( S gii thch khn phn bi tp).

+ Cc bi tp d thy nht: l xc nh v tr vn trng, m s vn trng, tnh bc sng, v,v,...

Bi 4: Tia Hng Ngoi - Tia T Ngoi - Tia X - Thang Sng in T.

Pht hin tia hng ngoi v t ngoi ngoi quang ph nh sng nhn thy, c hai u v tm, cn c nhng bc x m mt khng nhn thy, nhngnh mi hn ca cp nhit in v bt hunh quang m ta pht hin c. Cc bc x gi l tia hng ngoi v tia tngoi.

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Dng ng Cu-lt-gi to ra tia X: (C bn)L ng thy tinh chn khng bntrong c hai in cc:- Catot K bng kim loi, hnh

chm cu lm cho cc electront FF hi t vo anot A- Anot A bng kim loi c khi

lng nguyn t ln v imnng chy cao lm ngui bng

ncDy FF c nung nng bngmt dng in, cc e bay t FFn p vo A lm pht ra tia X.

Dng ng Rn - ghen to ra tia X: (Nng cao)_ t vo hai cc anot v catot ng Rn-ghen mt in pkhng i vo khong vi chc ngn Vn xut hinin trng E rt mnh lm tng tc cc ion (+) p mnhvo K to nn hin tng " bc x nhit" electron.

_ Sau khi bc x nhit, cc e chuyndi c hng v "icatot" dng in tc thi sinh ra t trng B.

_ i K chn t ngt dng in ny lm t trng gim t ngt v theo l thuyt Maxwell (in t trng) cmt in trng xoy xut hin hnh thnh sng in tTia X.

Cc tia hng ngoi - t ngoi - tia X

Tiu Tia hng ngoi(IR) Tia t ngoi(UV) TiaRn - ghen (X)

Bn cht Cng l Sng in t nhng c bc sng khc nhau

Bc sng 7,6.10-7m 10-3m. 3,8.10-7m 10-8m 10-8m 10-11m

Ngun pht - Vt nhit cao hn mi trngtrn 00K u pht tia hng ngoi:Bng n dy tc, bpga, bpthan, it hng ngoi, c th conngi(9m),...- 50% bc x Mt Tri- t

oC < 500

oC ch pht IR

- Vt c nhit to

C 20000

C:n h quang, n thu ngn(ph bin nht),...- 9% bc x Mt Tri.

- ng tia X- ng Cu-lit-gi- Phn ng ht nhn

Tnh cht Truyn thng, phn x, khc x, giao thoa, nhiu x, tc dng nhit, tc dng ln knh nh (phim)- Tc dng nhit: Lm nng vt(ni bt nht).- Gy ra mt s phn ng ha hc.

- Gy ra hin tng quang in trong, ngoi.- Lm pht quang ca mt s cht, lm ion ha cht kh, c tcdng sinh l, hy hoi t bo, dit khun.

- Gy ra hin tng quang in

trong ca cht bn dn (Xemchng lng t nh sng)- Bin iu sng in t. (Xemchng dao ng in t)

- B nc v thu tinh hp th- 0,18 m 0,4m qua cthch anh.- Tng zn hp th hu ht cctia c di 300nm v l tmo gip bo v ngi v sinhvt trn mt t khi tc dngca cc tia t ngoi t Mt Tri.

- C kh nng m xuyn

mnh, qua Al vi cmkhng qua Pb dy vi mm.(ni bt nht)- Tia X c bc sng cngngn th kh nng mxuyn cng ln; l tia Xcng.

ng dng - Sy kh, si m.- Lm b phn iu khin t xa(Remote ...- Chp nh mt t t v tinh.

- Trong qun s: Tn la tm mctiu; chp nh quay phim HN; ngnhm hng ngoi quan st banm...

- Tit trng thc phm, dng cy t,- Tm vt nt trn b mt sn

phm

- Cha bnh ci xng.

- Chp X quang; chiuin- Chp nh bn trong sn

phm, kim tra hnh l khi

i my bay.- Cha bnh ung th

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Thang sng in t:+ Sng v tuyn, tia hng ngoi, nh sng nhn

thy, tia t ngoi, tia Rnghen, tia gamma l sngin t.

+ Cc loi sng in t c to ra bi nhng cchrt khc nhau, nhng v bn cht th chng cng ch lmt v gia chng khng c mt ranh gii no r rt.

+ Tuy vy, v c tn s v bc sng khcnhau, nncc sng in t c nhng tnh cht rt khc nhau (cth nhn thy hoc khng nhn thy, c kh nng mxuyn khc nhau, cch pht khc nhau, v,v,...).

+ Cc tia c bc sng cng ngn (tia X, tia gamma)c tnh cht m xuyn cng mnh, d tc dng ln knhnh, lm pht quang cc cht v d ion ha khng kh.

+ Vi cc tia c bc sng di ta d quan st hintng giao thoa.

Bi 5: Cc V D Bi TpV Lng knh- Tn Sc nh Sng- Quang ph.Lng knh c gc chit quang A 10o v gc ti i 10

o th:

+ Gc hp bi hai tia n sc 1v 2l = |n

1- n

2|A

+ Khong cch gia hai n sc trn mn E l: x = L= L|n 1- n2|A(phi i sang rad)

(y cng l rng quang ph lin tc quan st c trn mn).+ Kt hp b cng thc v lng knh (xem bi 1, trang 1)

VD1: Gc chit quang ca mt lng knh bng 60. Chiu mt tia sng trng vo mt bn ca lng knh theo phngvung gc vi mt phng phn gic ca gc chit quang. t mt mn quan st sau lng knh, song song vi mt phn

gic ca gc chit quang v cch mt ny 2m. Chit sut ca lng knh i vi tia l n= 1,50 v i vi tia tm l

nt= 1,56. rng ca quang ph lin tc trn mn quan st bng:A. 6,28mm. B. 12,60 mm. C. 9,30 mm. D. 15,42 mm.

HD gii:Gc lch ca tia v tia tm qua LK

D= (n1)A = 30

Dt= (nt1)A = 3,360

rng ca quang ph lin tc trn mn quan sta = T = OT OOT = dtanD=tdDt, O = dtanDdD

a = d(Dt - D) = d.0,36.180

= 0,01256m

a = 12,56mn 12,6 mm. p n B

d = 2mO

T

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VD2:Mt tia sng trng chiu ti mt bn ca mt lng knh thu tinh tam gic u. Tia l mu vng qua lng knh cgc lch cc tiu. Bit chit sut ca lng knh i vi nh sng vng, nh sng tm ln lt l n v= 1,5 v nt= 1,52.Gc to bi tia l mu vng v tia l mu tm c gi tr xp x bng:

A. 0,770 B. 48,59

0C. 4,46

0 D. 1,730.

HD gii: Tia vng c gc lch cc tiu nn r1=A

2= 300

Nn sini = nVsin 300 i = iV= 48, 59

0

Sinrt =sini

nt= 0,493 rt= 29,57

o

rt+ r't = A r'

t= 30,43

0

Mt khc, sinit= n.sinr'tit= 50,34

0

Gc to bi tia l mu vng v tia l mu tm c gi tr xp x bng: 50,34- 48,59 = 1,75o Chn D

VD3: Mt lng knh thy tinh c tit din thng l tam gic u ABC. Chiu mt tia sng trng vo mt bn AB calng knh di gc ti i. Bit chit sut lng knh i nh sng v nh sng tm ln lt n = 1,643, nt =1,685. ctn sc ca tia sng trng qua lng knh th gc ti i phi tha mn iu kin

A. 32,960i 41,270 B. 0 i 15,520 C. 0 i 32,960 D. 42,420 i 900HD gii:Tnh gc gii hn caphn x ton phn ca tia v tm l

+ : 049,371

sin i

n

i

v i vi n sc tm: 04,36'1

'sin i

n

i

t

c tn sc nh sng th khng xy ra phn x ton phn+ Tia : r< i m r+ r=A r > A - i = 60o - 37,49

o = 22,51

o

Gc ti l sin ti >

t in 51,22sin >38,90

+ Tia tm : r > 60o - 36,4o = 23,6

o

sinti > nt.sin23,6 it > 42,42

o Chn p n D

Bi 6: Cc Dng Bi Tp VGiao Thoa Vi nh Sng n Sc.Dng 1:V tr vn sng- v tr vn ti- khong vn:

a - Khong vn: l khong cch gia 2 vn sng lin k : i =a

D. ( i ph thuc )

khong vn ca cc nh sng n sc khc nhau l khc nhau vi cng mt th nghim.b - V tr vn sng bc k: Ti ng vi d = d2d1= k., ng thi 2 sng nh sng truyn ti cng pha:

xks = kDa

= ki. vik = 0: ngvivn sng trung tm (hay d = 0)

k = 1: ng vivn sngbc1k= n: ngvivn sngbcn.

c - V tr vn ti th k + 1: Ti ng vi d =(k + 0,5). L v tr hai sng nh sng truyn ti ngc pha nhau.:

xk + 1T = (k + 0,5)

Da

= (k + 0,5)i VD:Vtr vn sngbc5 l: x 5

S= 5.i

Vtr vn tith4: x 4T

= 3,5.i (Sthvn0,5).

Dng 2:Khong cch gia cc vn:+Loi 1- Khong cch vn cng bn cht lin tip: l= (s vn 1).i

+Loi 2- Gia mt vn sng v mt vn ti bt k:Gi s xt khong cch vn sng bc k v vn ti th k, v tr: x k

s= k.i; x

k

T=(k'0,5).i

Nu:Hai vn cng pha so vivn trung tm: x =

'k

t

k

s xx

Hai vn khc pha so vivn trung tm: 'kt

k

s xxx

Do , khong cch gia vn sng v vn ti link l :

v tr vn ti cc th lin tip c xc nh:t

x = ki

2(vi k l: 1,3,5,7,.)

+Loi 3- Xc nh v tr M trn vng giao thoa cch VTT 1 khong x

Mc VS ? VT ? bc my ?Lp t s: M

xn

i

Nun nguyn, hay n Z, th tiM c vn sngbck = n.Nun bn nguyn hay n = k + 0,5 vik Z, th tiM c vn tithk +1

V

T

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Dng 3:Xc nh s vn sng, vn ti trn trng giao thoa:Gi L l b rng giao thoa trng. xc nh s vn sng (VS), vn ti (VT) trn trng giao thoa:

Lp t sL2i

= k + xtrong k lphnnguynx lphnl

+Nux < 0,5

sVS = 2k + 1sVT = 2k

+Nux 0,5 sVS = 2k + 1sVT = 2k + 2

Dng 4:Giao thoa vi Khe Young trong mi trng c chit sut n:Gi , ' ln lt lbcsng nh sng trong chn khng (khng kh) v trong mi trng c chit sut n.

Khi ' =n

th

Vtr vn sng: x =k 'D

a

=

k D

n.a

Vtr vn ti:x = (k + 0,5)'Da

= (k + 0,5)Dna

Khongvn: i ='Da

=Dna

Dng 5:Giao thoa vi Khe Young khi thay i khong cch D t hai khe n mn E:

Ta c: i =Da

i t l thun vi D

Do

khi khongcch l D: i = Da

khi khongcch l D:i=D'a

Khi i

i'=

D

D'

+ Nu D = D D > 0 Ta dch mn ra xa (ng i > i)+ Nu D = D D < 0 Ta amn li gn (ng i < i).

Dng 6:Giao thoa vi Khe Young khi dch chuyn hai khe theo hng song song vi mn E nhng vnnhn SI lm trung trc: (S l ngun s cp, I l trung im S 1S

2).

Ta c: i =Da

i t l nghch a

Do

khi khongcch l a: i = Da

khi khongcch l a' : i' =Da'

Khi i

i'=

a'

a

Dng 7:Giao thoa vi Khe Youngkhi tnh tin ngun s cp S i hoc theo hng song song vihai khe.

Cch gii dng ton ny l thit lp " Tam gic ng dng "Xt SIS' ng dng OIO' (g - g)

Khi SS'

OO'=

SI

IO.

Da vo s tnh tinca ngunta bit c v tr vn trung tm chuyn

di ntn? h vn chuyn di ntn ?Do nu tnh tin ngun S i ln th VTT s tnh tin i xung vngc li.

Dng 8:Giao thoa vi Khe Young khi t bn mng song songtrc mt khe.Thnghim Young c bn mt song song :- Do c bn mng c b dy l e, chit sut n :

+ Quang l t S1n M l : S1M = (d1e) + n.e+ Quang l t S2n M l : S2M = d2

- Hiu quang trnh : = S2MS1M = d2d1e(n - 1) =ax

D- e(n - 1)

- V tr vn sng : xs= ka

D + )1(. na

De

S1

DS2

d1

d2IO

xM

a

M

O

D

1S

2

S

1d

2d

xe

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- V tr vn ti : xt= (k + 0,5)a

D+ )1(

.n

a

De

- H vn di mt on 0x v pha c t bn mt song song: xo=

eD

a(n - 1)

Bi 7: Cc Dng Bi Tp V Giao Thoa Vi nh Sng Trng. (0,38 m 0,76 m)Nhn xt: Khi thc hin giao thoa vi nh sng trng ta thy:

+ chnh gia mi nh sng n sc u cho mt vch mu ring, tng hp ca chng cho ta vch sng trng (Do

s chng chp ca cc vch mu n tm ti v tr ny)

+ Dotmnh hn khong vn itm.=tmD

anh hn

lm cho tia tm gn vch trung tm hn tia (Xt cng mt bc giao thoa)+ Tp hp cc vch t tm n ca cng mt bc (cng gi tr k) quang ph ca bc k , (V d: Quang ph

bc 2l bao gm cc vch mu t tm n ng vi k = 2).

Dng 1:Cho ta x0trn mn, hi ti c nhng bc x no cho vch ti hoc sng?Cc bc x ca nh sng trng cho vn sng ti x0khi:Ti x0c th l gi tr i s xc nh hoc l mt v tr cha xc nh c th.

V tr vn sng bt k x =kD

a

V x = x0nn: x0=kD

a=

ax okD

. vi iu kin 12. ( thng thng

1

tmv

2

)

Gii h bt phng trnh trn ax o

2D

k ax o

1D

(k Z)

Do k Z, ta s chn tm c k ? tnh , cng l bc sng ca cc bc x ca A'S trng cho vn sng.Cc bc xca nh sng trng cho vn titi x0khi:

Mt cch tng t ta cng d dng thit lp c cng thc:ax o

2D

2k + 1 ax o

1D

(k Z)

Dng 2:Xc nh brng quang ph bc k trong giao thoa vi nh sng trng- B rng quang ph l khong cch gia vn sng mu ngoi cng v vn sng mu tm ca mt vng quang ph.

x k= (x

)k- (x

tm)

k x

k=

kDa

( -

tm) = k(i

- i

tm)(vi k N, k l bc quang ph).

Bi 8: Cc Dng Bi TpV Giao Thoa Vi Nhiu nh Sng n Sc.Dng 1:Giao thoa vi hai nh sng n sc 1v

2.

Nhn xt:Khi chm a sc gm nhiu bc x chiu vo khe I-ng to ra giao thoa. Trn mn quan st c h vngiao thoa ca cc bc x trn. Vn trung tm l s chng chp ca cc vn sng bc k = 0 ca cc bc x ny. Trn mn thuc s chng chp: +Ca cc vch sng trng nhau.

+ Cc vch ti trng nhau.+Hoc vch sng trng vch ti gia cc bc x ny.

Loi 1:Xc nh v tr vn hai vn sng trng.

Bc 1: V tr vn sng ca 2 bc x n sc trng nhau:x = k1 1D

a= k2

2Da

( Do cng a v D)

k1i1= k

2i

2k

1

1= k

2

2(k

1, k

2Z)

Bc 2: Xc nh "Bis chung nh nht" (BSCNN) ca k1v k2.

Trng hp vi 2 bc x ta ch cn lp t s 1 2

=k2k1

=n

m

Khong cch ngn nht gia 2 vn trng: Ti v tr c k1= k2= 0l vn trng trung tm, do khongcch gn nhau nht gia hai vn trng ng bng khong cch t vn trng trung tm n vn trng bc 1 ca

c 2 nh sng n sc: x = k1

1= k2

2 vi k min 0 N.

Loi 2:S vch sng, s vch trng ca hai vn sng quan st c.

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Gieo hnh vi gt thi quen. Gieo thi quen gt tnh cch. Gieo tnh cch gt s phn. ( Dick Lyles)10

+ Khi c giao thoa th 2 vn sng ca 2 bc x trng nhau: k1i1= k

2i

2

k

1

k2

= 2 1

=p

q( Nhp vo my tnh s cho t s ti gin)

k

1= pn

k2= qn

V tr trng l:

x = xk

1

(S, 1)= np

1Da

x

= xk2(S, 2)= nq

2Da

(n Z) (1)

+ S vch trng quan st c trn trng giao thoa L:-L

2

x

L

2

(*)

Thay mt trong hai biu thc x (1) vo (*) ta s c tp nghim ca n.Vi mi gi tr n mi gi tr k s vch sng trng l s gi tr n tha mn (*).

+ Xt s vn trng trn on MN L:Gi s x M< x

Nth x

Mx

x Nkhong n s gi tr n l s vn trng thuc on MN.

+ Ch : Nu M, N l s vn sng trng:

S vch quan st c trn trng L: N S/L= N

1

S/L+ N

2

S/L- N S trng/ L

S vch quan st c trn on MN: N S/MN= N

1

S/MN+ N

2

S/MN- N S trng/MN

Loi 3:Xc nh v tr hai vn ti trng.

+ Khi vn ti ca 2 bc x trng nhau: x 1

= x 2

(k1+ 0,5)

1Da

= (k2+ 0,5)

2Da

k

1+ 0,5

k2+ 0,5

= 2 1

=p

q(t s ti gin)

k1+ 0,5 = p(n + 0,5)

k2+ 0,5 = q(n + 0,5). V tr trng ca vn ti xT

= xk1(T, 1)= p(n + 0,5)

1Da

Tng t x nmtrong vng kho st:-L

2x

L

2(Vi mi gi tr n thu c v tr vn ti trng).

+ S vn ti trng trn on MN: x Mxx

N( tng t nh vn sng)

Loi 4: Xc nh v tr vn sng ca bc x ny trng vi vn ti ca bc x kia.

Gi s: xk1(S, 1)

= xk2+ 1

(T, k2)k1i

1= (k

2+ 0,5)i

2

k1k2+ 0,5

=i 2i 1

=

2

1=

pq

(t sti gin)

k

1= p(n + 0,5)

k2+ 0,5 = q(n + 0,5)

v tr trng x = p(n + 0,5)i1

-L

2x

L

2s VS v VT trng nhau chnh l s gi tr n tm c.

Ch : c th xt ngc li xk1+ 1

(T, 1)= xk2(S, 2) ( Ngoi ra c th dng PP th p n tm nhanh ra p s!)

Dng 2:Giao thoa vi chm ba nh sng n sc 1, 2v

3. ( c th tng ln n n bc x

n)

B1: Thit lp v tr vn trng k11= k

2

2= k

3

3.

B2: Tm bi s chung nh nht (BSCNN) ca 1, 2,

3

B3: Xc nh s vn trng ca c 3 bc x.B4: Xc nh s vn trng ca tng cp bc x 12,

23,

31.

Vn t ra l lm sao tm BSCNN k 1,2,3= BCNN(1, 2, 3) nhanh nht c th ?Mc d tham kho kh nhiu cch, trong c cch s dng my tnh VINACAL fx-570 ES Plus tm BCNN,UCLN, phn tch s nguyn t, tm nguyn v d trong php chia,... thy vn nhn thy rng cch ti u nht l dngTon hc trong tnh hung ny l tt nht.

tm BSCNN ta lm nh sau:

Bc 1:Phn tch cc s

s nguyn t( SNT l s ch chia ht cho 1 v cho chnh n)Gi s ta c ba s x 1, x

2, x

3. a cc s v SNT, ta ln lt ly s {x

1} chia cho cc s nguyn t

{2;3;5;7;11;13;17;..} cho n khi chia ht th ngng.

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Khi cc s s c biu din di dng:x

1= a

n .b

m .c

p .d

q ...

x2= a

n' .b

m' .c

p' .d

q' ...

x3= a

n'' .b

m'' .c

p'' .d

q'' ...

(Vi a,b,c,d l cc SNT; n,m,p,q N)

Bc 2:BSCNN {x 1, x2, x

3} = a

n max

.bm max

.cp max

. dq max

...

Bc 3: Khi k11= k

2

2= k

3

3= BSCNN {x

1, x

2, x

3}

k1= ?k2= ?k3= ?

v tr trng nhau ca3 bc x.

cc em hiu r hn, thy xt v d sau:

VD:Trong th nghim I-ng v giao thoa nh sng, hai khe c chiu ng thi 3 bc x n sc c bcsng : 1= 0,4m , 2= 0,5m , 3= 0,6m. Trn mn quan st ta hng c h vn giao thoa, trong khonggia hai vn sng gn nhau nht cng mu vi vn sng trung tm, ta quan st c bao nhiu vn sng?HD gii:

Xt vn trng vn: k11= k

2

2= k

3

34k

1= 5k

2= 6k

2

Ta c4 = 2

2

5 = 516 = 21 . 3

1

BSCNN{4;5;6} = 22 .31 .5

1 = 60.

Khi : 4k1= 5k2= 6k

2= 60

k

1= 15

k2= 12

k3= 10

y l v trc 3 bc x trng nhau gn nht vi VTT (trng u tin)

Do trong khong VSTT(k = 0 trng u tin)

VS m c 3 bc x trng nhau gn nht.

N

S

1= 15 - 1 = 14 VS

NS

2= 12 - 1 = 11 VS

NS

3= 10 - 1 = 9

Hin ti ta quan st c 14 + 11 + 9 = 34 VS

Nhng ci hay v cng l ci kh ca bi ton nm ch, trong khong li c s trng nhau ca cc bc x 12,23,

31. V vy ta li phi tnh tip s vn trng ca cc bc x tr ra.

Xt s trng nhau ca 1v 2ta c:

k2

k1

=4

5=

8

10=

12

15=

16

20=

20

25=

24

30=...

(Vn l bit khi no dng li ?, ta chn ngay k2= 12, k1= 15, l v tr gii hn)

trong khong c 2 v tr trng nhau {(4;5),(8,10)} ca 1v 2. N

12= 2

Mt cch tng t:

k3

k2=

5

6=

10

12N

23= 1k1k

3

=2

3=

4

6=

6

9=

8

12=

10

15N

13= 4

Do s VS quan st tht s l NS

123

= NS

1+ N

S

2+ N

S

3- (N

12 + N

23

+ N

13) = 34 - (2 + 4 + 1) = 27 VS

V y l hnh nh khi giao thoa vi 3 bc x ( 1= 0,4 m, 2= 0,5 m,

3= 0,6 m)

3

1

2

Hnh nh tht !

Bi 9: CcDng Bi Tp V ng Tia X - ng Cu-lt-giBc sng ca tia X:

+ nnglngeletron khi iviCatod: " xc " Ae= e.U

AK(Theo thuytPlanck)

+ nnglngphoton catia X: " hn" X= hc = hf (Theo thuytEinstein) (h = 6,625.10-34 ) J.s

Khi electron va chm vo i Catod th nng lng e tr thnh nng lng photon ca tia X:

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+ nh l ng nng: " Cng ca lc in trng bng bin thin ng nng ": |e| U AK=hc

=12

mv2 max

+ Do hc

min

= hfmax=12mv2 max. Trong v

maxl vntcccicae khi pvo catod

Nhit lng sinh ra bi dng in l Q = A mct = U AK.It Trong m l khilng

c l nhitdung ringt l tngnhit

Cng dng in qua ng Rn-ghen: I =q

t=

n|e|

t

Cng sut ta nhit ca ng Rn-ghen lm nng i Catod: P nhit= UI.a% = P

hao ph( P nhitchim hn 99% hay a% > 99% )

Cng sut bc x ca ng Rn-ghen: P X= UI.b% = P

ch( PXchim t hn 1% hay b% < 1%)

Cng sut ton phn: P = P nhit+ P

ch= UI

Hiu sut ng Rn-ghen: H =P ch

P

tonphn

Cc hng s cn lu :m

e= 9,1.10

-31 kg

h = 6,625.10-34

J.s

c = 3.108 m/s

Bi 10: Nhng Lu khi nh trc nghim l thuyt phn sng nh sng.Trong TN GTAS, nu che 1 trong 2 khe sng th khng cn hin tng GTAS na. Lc ti mi im trn mn

c sng bng na sng ca VS trc khi che.Cc b phn ca my quang ph c b tr theo th t: ng chun trc - Lng knh - Bung nh, trong lng

knh l b phn quan trng nht.Chm AS trng ca ASMT hay AS a sc khng c bc sng nht nh.ASMT c mi tia trong thang sng in t. Cc tia trong thang sng in t u khng mang in nn khng b

lch trong in trng v t trng.Hin tng th hin AS c tnh cht sng l: GTAS, Tn sc AS, Nhiu x AS, tia Laser,...Hin tng th hin l s giao thoa nh sng: a CD, vng du m, git nc, bong bng x phng,...'c im chung ca c 3 tia hng ngoi (IR - infrared Rays), t ngoi (UV - ultra Violet) v tia Rn-ghen (X Rays)

l u tc dng ln knh nh, phim nh.

c im ni bt ca tia hng ngoi: tc dng nhit ngdng sy kh, si m.

c im ni bt ca tia X: m xuyn:c thqua cmnhAl vi cmnhngkhng thqua cmingPb vi mm

ng

dng Kim tra hnh l.

ngdng ni bt ca tia t ngoi:chabnhci xng

tm vtnttrn bmtsnphmkhtrng, ditkhun

ng dng ni bt ca tia X:ChpX quang, chabnhung thd tm khuytttbn trong snphm

nh sng Mt Tri m con ngi thu c Tri t khng phi lquang ph lin tc (QPLT) m l quang phvch hp th. (Do ASMT khi truyn ti Tri t b kh quyn Mt tri (sc cu v nht hoa), cng vi tng Ozone Tri t hp th bt mt phn ch thu c mt phn QP vch hp th).

i vi QPLT th tc nhn gy ra l do cht rn, lng, kh p sut ln bnung nng.Cn i QP vch pht x ldo cht lng hay kh p sut thp b kch thch.i vi QPLT th ch chu s ph thuc vo to ca vt ch khng ph thuc vo bn cht cu to ca vt.

CHC CC EM N TP HIU QU V T KT QU CAO NHT TRONG KTHI TUYN SINH I HC 2014

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