Chng IV

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Chng I: in tch - in trng.

1. Vt nhim in_ vt mang in, in tch_ l vt c kh nng ht c cc vt nh.

C 3 hin tng nhim in l nhim in do c xt, nhim in do do tip xc v nhim in do hng ng.

2. Mt vt tch in c kch thc rt nh so vi khong cch ti im ta xt c gi l in tch im.

3. Cc in tch cng du th y nhau, tri (ngc) du th ht nhau.

4. nh lut Cu_Lng (Coulomb): Lc ht hay y gia hai in tch im t trong chn khng c phng trng vi ng thng ni hai in tch im , c ln t l thun vi tch ln ca hai in tch v t l nghch vi bnh phng khong cch gia chng

Cng thc:

Vi k = ()

q1, q2 : hai in tch im (C )

r : Khong cch gia hai in tch (m)

5.Lc tng tc ca cc in tch trong in mi (mi trng ng tnh)

in mi l mi trng cch in.

Cc th nghim chng t rng, lc tng tc gia cc in tch im t trong mt in mi ng cht, chim y khng gian xung quanh in tch, gim i ln khi chng c t trong chn khng:

: hng s in mi ca mi trng. (chn khng th = 1)

6. Thuyt electron (e) da vo s c tr v di chuyn ca cc e gii thch cc hin tng in v cc tnh cht in ca cc vt. Trong vic vn dng thuyt e gii thch cc hin tng nhim in (do c xt, tip xc, hng ng), ta tha nhn ch c e c th di chuyn t vt ny sang vt kia hoc t im ny n im kia trn vt.

7.cht dn in l cht c nhiu in tch t do,cht cch in(in mi) 8. nh lut bo ton in tch: Trong mt h vt c lp v in, tng i s ca cc in tch l khng i.- Quy tc tng hp lc: Quy tc hnh bnh hnh

Nu vt chu tc dng ca 2 lc th

+

+

+

+

Nhn xt: IU KIN CN BNG CA MT IN TCH.

PP Chung

Khi kho st iu kin cn bng ca mt in tch ta thng gp hai trng hp:

(. Trng hp ch c lc in:

- Xc nh phng, chiu, ln ca tt c cc lc in , , tc dng ln in tch xt.

- Dng iu kin cn bng:

- V hnh v tm kt qu.

(. Trng hp c thm lc c hc (trng lc, lc cng dy, )

- Xc nh y phng, chiu, ln ca tt c cc lc tc dng ln vt mang in m ta xt.

- Tm hp lc ca cc lc c hc v hp lc ca cc lc in.

- Dng iu kin cn bng: ( (hay ln R = F).

2. in trng.

- in trng tnh l do cc ht mang in ng yn sinh ra.

- Tnh cht c bn ca in trng l n tc dng lc in ln in tch t trong n.

- Theo quy c v chiu ca vect cng in trng: Vct cng in trng ti mt im lun cng phng, cng chiu vi vect lc in tc dng ln mt in tch dng t ti im trong in trng.PP Chung

(. Cng in trng ca mt in tch im Q:

p dng cng thc . q1(----------------- q1(-------------------

(Cng in trng E1 do q1 gy ra ti v tr cch q1 mt khong r1 : ,

Lu cng in trng E l mt i lng vect. Trong chn khng, khng kh ( = 1)

n v chun: k = 9.109 (N.m2/c2 ), Q (C), r (m), E (V/m)

3. Cng ca lc in v hiu in th.

1. Khi mt in tch dng q dch chuyn trong in trng u c cng E (t M n N) th cng m lc in tc dng ln q c biu thc: A = q.E.d

Vi: d l khong cch t im u ( im cui (theo phng ca ).

V th d c th dng (d> 0) v cng c th m (d< 0)

C th nh hnh v: khi in tch q di chuyn t M( N th d = MH.

V cng chiu vi nn trong trng hp trn d>0.

Nu A > 0 th lc in sinh cng dng, A< 0 th lc in sinh cng m.

2. Cng A ch ph thuc vo v tr im u v im cui ca ng i trong in trng m khng ph thuc vo hnh dng ng i. Tnh cht ny cng ng cho in trng bt k (khng u). Tuy nhin, cng thc tnh cng s khc.

in trng l mt trng th.

3. Th nng ca in tch q ti mt im M trong in trng t l vi ln ca in tch q:

WM = AM( = q.VM.

AM( l cng ca in trng trong s dch chuyn ca in tch q t im M n v cc. (mc tnh th nng.)

4. in th ti im M trong in trng l i lng c trng cho kh nng ca in trng trong vic to ra th nng ca in tch q t ti M.

5. Hiu in th UMN gia hai im M v N l i lng c trng cho kh nng sinh cng ca in trng trong s di chuyn ca in tch q t M n N.

6. n v o in th, hiu in th l Vn (V)Dng 1: TNH CNG CA LC IN. HIU IN TH.

PP Chung

- Cng ca lc in tc dng ln mt in tch khng ph thuc vo hnh dng ng i ca in tch m ch ph thuc vo v tr ca im u v im cui ca ng i trong in trng. Do , vi mt ng cong kn th im u v im cui trng nhau, nn cng ca lc in trong trng hp ny bng khng.

Cng ca lc in: A = qEd = q.U

Cng ca lc ngoi A = A.

nh l ng nng:

Biu thc hiu in th:

H thc lin h gia cng in trng hiu in th trong in trng u:

4. T in.

- Cng thc nh ngha in dung ca t in:

- in dung ca t in phng:

- in dung ca n t in ghp song song:

C = C1 + C2 + ......+ Cn- in dung ca n t in ghp ni tip:

- Nng lng ca t in:

- Mt nng lng in trng:

1. T in l mt h gm hai vt dn t gn nhau v cch in vi nhau. T in dng tch in v phng in trong mch in. T in thng dng l t in phng.

K hiu ca t in:

2. Ni hai bn ca t in vi hai cc ca ngun in th t in s b tch in. ln in tch hai bn t bao gi cng bng nhau nhng tri du. Ngi ta gi in tch ca t in l in tch ca bn dng.

3. i lng c trng ca t in l in dung ca t. in dung C ca t in l i lng c trng cho kh nng tch in ca t in mt hiu in th nht nh. N c o bng thng s ca in tch Q ca t vi hiu in th U gia hai bn ca n.

n v o in dung ca t in l fara (F)

1 mF = 10-3 F.1 (F = 10-6 F.

1 nF = 10-9 F.

1 pF = 10-12 F.

- in dung ca t in phng:

Trong : ;

Lu : Trong cng thc , ta thng lm tng C l i lng ph thuc vo Q, ph thuc vo U. Nhng thc t C KHNG ph thuc vo Q v U.

4*. Ghp t in (xem k):

Ghp ni tip:

Ghp song song:

C1 C2 Cn

Cb = C1 + C2 + ... + Cn.

Qb = Q1 + Q2 + + Qn.

Qb = Q1 = Q2 = = Qn.

Ub = U1 + U2 +...+ Un.

Ub = U1 = U2 = = Un.

5. in trng trong t in mang mt nng lng l:

=cu^2/2

- in trng trong t in l in trng u.

- Cng thc lin h gia cng in trng E bn trong t in, hiu in th U v khong cch d gia hai bn l:

- Nu cng in trng trong lp in mi vt qu mt gi tr gii hn Emax th lp in mi tr thnh dn in v t in s b hng. Nh vy, hiu in th gia hai bn t in khng c vt qu gii hn c php: Umax = Emax.d

Dng : GHP T IN CHA TCH IN.

PP Chung:

- Vn dng cc cng thc tm in dung (C), in tch (Q), hiu in th (U) ca t in trong cc cch mc song song, ni tip.

- Nu trong bi ton c nhiu t c mc hn hp, ta cn tm ra c cch mc t in ca mch ri mi tnh ton.

- Khi t in b nh thng, n tr thnh vt dn.

- Sau khi ngt t in khi ngun v vn gi t in c lp th in tch Q ca t vn khng thay i.

( i vi bi ton ghp t in cn lu hai trng hp:

+ Nu ban u cc t cha tch in, khi ghp ni tip th cc t in c cng in tch v khi ghp song song cc t in c cng mt hiu in th.

+ Nu ban u t in (mt hoc mt s t in trong b) c tch in cn p dng nh lut bo ton in tch (Tng i s cc in tch ca hai bn ni vi nhau bng dy dn c bo ton, ngha l tng in tch ca hai bn trc khi ni vi nhau bng tng in tch ca chng sau khi ni).

CHUYN NG CA HT MANG IN TRONG IN TRNG( Khi ht mang in c th t do khng vn tc u trong mt in trng u th di tc dng ca lc in , ht mang in chuyn ng theo mt ng thng song song vi ng sc in.

Nu in tch dng (q >0) th ht mang in (q) s chuyn ng cng chiu in trng.

Nu in tch m (q E2 th

Eb = E1 - E2rb = r1 + r2v dng in i ra t cc dng ca E1.

- Mc song song: (n ngun ging nhau)

Eb = E v rb =

1. nh lut m i vi ton mch: Cng dng in chy trong mch in kn t l thun vi sut in ng ca ngun in v t l nghch vi in tr ton phn ca mch .

+ - ((, r ( ( = I.RN +I.r I

Vi I.RN = UN : gim th mch ngoi.

I.r: gim th mch trong.

( UN = ( - r.I

+ Nu in tr trong r = 0, hay mch h (I = 0) th UN = (.

+ Nu R = 0 th , lc ny ngun gi l b on mch.

nh lut m i vi ton mch hon ton ph hp vi nh lut bo ton v chuyn ha nng lng.

Theo nh lut bo ton v chuyn ha nng lng ta c: Cng ca ngun in sinh ra trong mch kn bng tng cng ca dng in sn ra mch ngoi v mch trong.

A = ( I.t = (RN + r).I2.t

Hin tng on mch xy ra khi ni 2 cc ca mt ngun in ch bng dy dn c in tr rt nh. Khi on mch, dng in chy qua mch c cng ln v c th gy ra nhiu tc hi.

2. nh lut m i vi oan mch:

I=

( on mch cha may thu: (, r

Th UAB = ( + I(R+ r)

Hay UBA = - ( - I (R +r).

( on mch cha nhiu ngun in, nhiu in tr: (1, r1 (2, r2

Th UAB = (1 - (2 + I (R1+ R2+ r1 +r2).

Hay: UBA = (2 - (1 I (R1+ R2+ r1 +r2).

3. Hiu sut ca ngun in: (%)

4. Mc ngun in:

( Mc n ngun in ni tip nhau.

(b = (1 + (2 + .. + (n

rb = r1 + r2 + .. + rn

( Mc m ngun in ging nhau ((0 , r0) song song nhau.

(b = (0 , rb =

( Mc N ngun in ging nhau ((0 , r0) thnh m dy, mi dy c n ngun in.

(b = n.(0 , rb = .

( Mc xung i. Gi s cho (1 > (2. (1, r1 (2, r2 (b = (1 - (2 , rb = r1 + r24. in nng v cng sut in. nh lut Jun Lenx

- Cng v cng sut ca dng in on mch (in nng v cng sut in on mch)

A = UIt; P = UI

- nh lut Jun Lenx:

Q = RI2t

- Cng v cng sut ca ngun in:

A = EIt; P = EI

- Cng sut ca dng c tiu th in:

Vi dng c to nhit: P = UI = RI2 =

Vi my thu in: P = EI + rI2(P /= EI l phn cng sut m my thu in chuyn ho thnh dng nng lng c ch, khng phi l nhit)

- n v cng (in nng) v nhit lng l jun (J), n v ca cng sut l ot (W).

Dng 1: VN DNG NH LUT JUN-LENX. CNG SUT IN.

PP chung:

Ap dng cng thc:

( Cng v cng sut ca dng in on mch: A = U.I.t , P =

( nh lut Jun-LenX: Q = R.I2.t hay Q=

( Cng sut ca dng c tiu th in: P = U.I = R.I2 =

- ch ny, cc cu hi v bi tp ch yu v: Tnh in nng tiu th v cng sut in ca mt on mch. Tnh cng sut ta nhit v nhit lng ta ra trn mt vt dn. Tnh cng v cng sut ca ngun in.

- Cn lu nhng vn sau:

+ Trong cc cng thc tnh cng, tnh nhit lng: c cng, nhit lng tnh ra c n v l Jun (J) cn ch i n v thi gian ra giy (s).

+ Mch in c bng n: R =

( Coi nh in tr khng ph thuc vo hiu in th t vo n, khng thay i theo nhit .)

Nu n sng bnh thng th Ithc = Im (Lc ny cng c Uthc = Um; Pthc = P m )

Nu Ithc < Im th n m hn bnh thng.

Nu Ithc > Im th n sng hn bnh thng.

Chng III. Dng in trong cc mi trng

1. Dng in trong kim loi

- Cc tnh cht in ca kim loi c th gii thch c da trn s c mt ca cc electron t do trong kim loi. Dng in trong kim loi l dng dch chuyn c hng ca cc lectron t do.

- Trong chuyn ng, cc lectron t do lun lun va chm vi cc ion dao ng quanh v tr cn bng cc nt mng v truyn mt phn ng nng cho chng. S va chm ny l nguyn nhn gy ra in tr ca dy dn kim loi v tc dng nhit. in tr sut ca kim loi tng theo nhit . in tr sut ( ca kim loi tng theo nhit gn ng theo hm bc nht :

( = (0(1 + ((t - t0))

H s nhit in tr khng nhng ph thuc vo nhit , m vo c sch v ch gia cng ca vt liu .

- Hin tng khi nhit h xung di nhit Tc no , in tr ca kim loi (hay hp kim) gim t ngt n gi tr bng khng, l hin tng siu dn.Hin tng nhit in. Cp nhit in l hai dy dn kim loi khc bn cht, hai u hn vo nhau. Khi nhit hai mi hn T1, T2 khc nhau trong mch c sut in ng nhit in

E = (T ( T1 T2 ) (T l h s nhit in ng.

2. Dng in trong cht in phn

- Dng in trong cht in phn l dng chuyn dch c hng ca cc ion dng v catt v ion m v ant. Cc ion trong cht in phn xut hin l do s phn li ca cc phn t cht tan trong mi trng dung mi.

Khi n cc in cc th cc ion s trao i lectron vi cc in cc ri c gii phng ra , hoc tham gia cc phn ng ph. Mt trong cc phn ng ph l phn ng cc dng tan, phn ng ny xy ra trong cc bnh in phn c ant l kim loi m mui cu n c mt trong dung dch in phn.

nh lut Fa-ra-y v in phn.

k =

Khi lng M ca cht c gii phng ra cc in cc t l vi ng lng gam ca cht v vi in lng q i qua dung dch in phn.

Biu thc ca nh lut Fa-ra-y

vi F 96500 (C/mol)

3. Dng in trong cht kh

- Dng in trong cht kh l dng chuyn dch c hng ca cc ion dng v catt, cc ion m v lectron v ant.

Khi cng in trng trong cht kh cn yu, mun c cc ion v lectron dn in trong cht kh cn phi c tc nhn ion ho (ngn la, tia la in....). Cn khi cng in trng trong cht kh mnh th c xy ra s ion ho do va chm lm cho s in tch t do (ion v lectron) trong cht kh tng vt ln (s phng in t lc).

S ph thuc ca cng dng in trong cht kh vo hiu in th gia ant v catt c dng phc tp, khng tun theo nh lut m (tr hiu in th rt thp).

- Tia la in v h quang in l hai dng phng in trong khng kh iu kin thng.

C ch ca tia la in l s ion ho do va chm khi cng in trng trong khng kh ln hn 3.105 (V/m)

- Khi p sut trong cht kh ch cn vo khong t 1 n 0,01mmHg, trong ng phng in c s phng in thnh min: ngay phn mt catt c min ti catt, phn cn li ca ng cho n ant l ct sng ant.

Khi p sut trong ng gim di 10-3mmHg th min ti catt s chim ton b ng, lc ta c tia catt. Tia catt l dng lectron pht ra t catt bay trong chn khng t do.

4. Dng in trong chn khng

- Dng in trong chn khng l dng chuyn dch c hng ca cc lectron bt ra t catt b nung nng do tc dng ca in trng.

c im ca dng in trong chn khng l n ch chy theo mt chiu nht nh t ant sang catt.

5. Dng in trong bn dn

- Dng in trong bn dn tinh khit l dng dch chuyn c hng ca cc lectron t do v l trng.

Tu theo loi tp cht pha vo bn dn tinh khit, m bn dn thuc mt trong hai loi l bn dn loi n v bn dn loi p. Dng in trong bn dn loi n ch yu l dng lectron, cn trong bn dn loi p ch yu l dng cc l trng.

Lp tip xc gia hai loi bn dn p v n (lp tip xc p n) c tnh dn in ch yu theo mt chiu nht nh t p sang n.Chng IV. T trng

1. T trng. Cm ng t

- Xung quanh nam chm v xung quanh dng in tn ti t trng. T trng c tnh cht c bn l tc dng lc t ln nam chm hay ln dng in t trong n.

- Vect cm ng t l i lng c trng cho t trng v mt tc dng lc t. n v cm ng t l Tesla (T).

Vc t cm ng t :

nh lut Am-pe, c im ca lc t , quy tc bn tay tri :

2. T trng ca dng in chy trong dy dn c hnh dng c bit

+Dng in thng di : ( quy tc nm tay phi)

+Dng in trn :

+ ng dy hnh tr :

-Nguyn l chng cht ca t trng ( t trng ca nhiu dng in):

3. c im Lc Lorenx , quy tc bn tay tri: trong = (,).+ Bn knh qu o :

+ Chu k ca chuyn ng trn u ca ht :

I/ Lc t tc dng ln mt on dy c mt dng in t trong t trng u

Lc t do t trng u tc dng ln on dy thng chiu di l (m) c dng in I (A) chy qua l lc c :

im t : trung im ca on dy .

Phg : vung gc vi mt phng (l ,) Chiu : c xc nh bi quy tc bn tay tri Xo bn tay tri hng cc ng cm ng t sao cho chiu ca dng in i t c tay n ngn tay . Ngn tay ci choi ra ch chiu ca lc t ln c xc nh theo cng thc Ampe :

F = B.I.l.sin vi II / Lc t tc dng ln gia 2 dy dn thng di song song c dng in chy qua .

Nu 2 dng in chy cng chiu 2 dy ht nhau.

Nu 2 dng in chy ngc chiu 2 dy y nhau.

Lc tc dng c ln : Trong : l cng dng in chy qua 2 dy dn .

l l chiu di 2 dy .

d khong cch 2 dy .

III/ Lc t tc dng ln khung dy c dng in .

Nu mt phng khung dy vung gc vi ng cm ng t khi cc lc tc dng ln khung khng lm quay khung ( ch lm cho khung gin ra hoc co li ) .

Nu mt phng khung dy song song vi ng cm ng t khi xut hin ngu lc lm khung quay vi momen : M = B.I.S. sin vi : S : din tch khung - : l php tuyn mt phng khung dy.Chng V. Cm ng in t

1. Khi nim t thng :,

- Hin tng cm ng in t, inh lut Len x v chiu dng in cm ng

2. nh lut Fa-ra day v cm ng in t :

+nu khung dy c N vng :

+* ln : 3. Hin tng t cm:

+ t cm :

t cm ca ng dy c li st : : t thm ca li st.

+Sut in ng t cm :

+ Nng lng t trng :

EMBED Equation.3 Chng VI. Khc x nh sng

1. Hin tng khc x nh sng, nh lut khc x nh sng ,

Chit sut t i:

2. Phn x ton phn, iu kin c phn x ton phn

+ nh sng truyn t mi trng chit quang hn sang mi trng chit quang km ( n1 > n2) .

+ Gc ti : .

Nu nh sng i t mi trng c chit sut n rakhng kh th: sin igh = .Chng VII. Mt v cc dng c quang hc

IV. Mt.Cc dng c quang

1. Cu to lng knh. Cc cng thc lng knh

, r+r = A, D = i + i A

+iu kin i, A 100 : i nr , i nr , A = r + r , D (n 1) A +iu kin gc lch cc tiu Dmin: i = i= im , r = r = , Dmin = 2im A , sin

Lu : Khi Dmin i= i : tia ti v tia l i xng nhau qua mt phn gic ca gc chit quang A.

2. Thu knh mng : TKHT-TKPK

+ nh ngha, phn loi, ng i ca tia sng qua thu knh, mi lin h gia nh v vt , Cch dng hnh( V tia sng), Tnh cht nh

+ Cng thc thu knh :

; ;

: d > 0 : vt tht ; d< 0 : vt o.

: d> 0 : nh tht ; d< 0 : nh o.

: f > 0 : TKHT ; f < 0 : TKPK

k > 0: nh v vt cng chiu

k < 0: nh v vt ngc chiu

+ t thu knh : D > 0:TKHT ; D < 0 : TKPK

Vi n: chit sut t i ca cht lm thu knh vi mi trng ngoi.

Quy c: R > 0: mt li ; R< 0: mt lm ; R= : mt phng.

+ Tiu c:

+ ng i ca tia sng:

- Tia ti song song trc chnh cho tia l c phng qua tiu im nh chnh F.

- Tia ti qua quang tm O th truyn thng.

- Tia ti c phng qua tiu im vt chnh F cho tia l song song trc chnh

- Tia ti song song v trc ph cho tia l c phng qua tiu im nh ph

+ S tng quan gia nh v vt: (vt nh chuyn ng cng chiu)

VTNH

Thu knh phn k+Vi mi vt tht d > 0

+Vt o:

d > 2f

d = 2f

f < d < 2f

nh o, cng chiu vi vt v nh hn vt 0 < d <

d > 0: nh tht, ngc chiu nh hn vt

d = 2 f: nh tht, ngc chiu bng vt

d> 2 f : nh tht, ngc chiu, ln hn vt

vt nh chuyn ng cng chiu

Thu knh hi t

+Vt tht

d= 0

0 < d< f

d = f

f < d < 2f

d = 2 f

d > 2 f

+ Vt o d = 0 : nh o cng chiu, bng vt

d< 0: nh o, cng chiu, ln hn vt

d = : nh o v cc d> 2 f: nh tht, ngc chiu, ln hn vt

d = 2 f : nh tht, ngc chiu, bng vt

f < d < 2 f: nh tht, ngc chiu, nh hn vt

nh tht, cng chiu vi vt v nh hn vt

* Khong cch vt nh:

*** T cng thc :

d2 Dd + Df = 0 = D ( D 4f )

D = d + d

+D> 4f : c 2 v tr TK nh trn mn. +D = 4f: c 1 v tr TK nh trn mn d = d=.

+ D < 4f : khng c v tr no ca TK nh trn mn.

= D2 4fD > 0

EMBED Equation.DSMT4;

c 2 v tr thu knh : d2 d1 = l

EMBED Equation.DSMT4= l

D

D2 4fD = l2 f =

+ H quang ( quang h) : S to nh ; cng thc :;

H hai thu knh c t D1 , D2 ghp st nhau , t tng ng : D = D1 + D2 .

GII BI TON V H THU KNH

I. Lp s to nh1. H hai thu knh ng trc ghp cch nhau S to nh:

L1 L2 AB (((( A1B1 (((( A2B2 d1 d1 d2 d2

Vi: d2 = O1O2 d1; k = k1k2 =

2. H hai thu knh ng trc ghp st nhau S to nh:

L1 L2 AB (((( A1B1 (((( A2B2 d1 d1 d2 d2

Vi: d2 = d1; k = k1k2 = = -

H thu knh tng ng vi mt thu knh c t D = D1 + D2.

t ca h hai thu knh mng

3. Mt : Cu to, s iu tit, im cc cn, im cc vin, gc trng vt,Cc tt ca mt v cch khc phc

- c im ca mt cn

+Khi khng iu tit , tiu im F nm trc mng li.

fmax < OV ; OCc < ; OCv <

EMBED Equation.DSMT4Dcn > Dthng

+ Cch khc phc: Mt phi eo 1 thu knh phn k sao cho qua knh nh ca cc vt hin ln im Cv ca mt. nn khi eo knh st mt th : fK = - OCv.

- c im ca mt vin : + Khi khng iu tit c tiu in nm sau mng li

fmax > OV ; OCC > ; OCv : o sau mt . Dvin < D thng.

+ Cch khc phc : eo mt thu knh hi t nhn vt gn nh mt thng, nh ca vt to bi knh l nh o nm CC ca mt vin.

4. Knh lp : nh ngha,cng dng,cch ngm chng im cc cn v ngm chng v cc, s bi gic

+ Tng qut :

+ Ngm chng cc cn:

EMBED Equation.3 + Ngm chng v cc :

5. Knh hin vi : Cu to, cng dng, cch ngm chng

+ Tng qut :

+Ngm chng v cc : ( )

6. Knh thin vn :

cu to,cng dng, cch ngm chng- Knh thin vn gm vt knh l thu knh hi t c tiu c ln v th knh l thu knh hi t c tiu c nh.

- Ngm chng l quan st v iu chnh khong cch qia vt knh v th knh sao cho nh ca vt nm trong khong thy r ca mt.

v S bi gic khi ngm chng v cc: G = k1.G2

(vi k1 l s phng i ca nh A1B1 qua vt knh, G2 l s bi gic ca th knh

(vi l di quang hc ca knh hin vi)

f1 : tiu c vt knh ; f2 : tiu c th knh ; l: khong cch gia vt knh v th knh

Ph bn

MT S KIN THC TOAN C BAN CN CHO VT LY

I. Tam thc bc hai.

a.x2 + b.x + c =0

iu kin co nghim:

Du bng xay ra phng trinh co nghim kep

II.Ham s bc hai.

y = a.x2 + b.x + c

a>0 Ham y(x) co b lom quay ln. Ta co cc tiu.

a