chuyÊn ĐỀ song anh sang.doc
TRANSCRIPT
CHUYN : LNG T NH SNG
CHUYN : LNG T NH SNG
A. TM TT L THUYT
I. Hin tng quang in(ngoi) - Thuyt lng t nh sng.
a. Hin tng quang in
Hin tng nh sng lm bt cc electron ra khi mt kim loi gi l hin tng quang in ngoi (gi tt l hin tng quang in).
b. Cc nh lut quang in
+ nh lut quang in th nht (nh lut v gii hn quang in):
i vi mi kim loi nh sng kch thch phi c bc sng ( ngn hn hay bng gii hn quang in (0 ca kim loi , mi gy ra c hin tng quang in: ( ( (0.
+ nh lut quang in th hai (nh lut v cng dng quang in bo ha):
l
e
c
h
f
h
.
.
=
=
i vi mi nh sng thch hp (c ( ( (0), cng dng quang
in bo ha t l thun vi cng chm nh sng kch thch.
+ nh lut quang in th ba
(nh lut v ng nng cc i ca quang electron):
ng nng ban u cc i ca quang electron khng ph thuc
vo cng ca chm sng kch thch, m ch ph thuc vo bc
sng nh sng kch thch v bn cht kim loi.
c. Thuyt lng t nh sng
+ Chm nh sng l chm cc phtn (cc lng t nh sng). Mi phtn c nng lng xc nh (nng lng ca 1 ph tn ( = hf (J). Nu trong chn khng th
f l tn s ca sng nh sng n sc tng ng. h=6,625.10-34 J.s : hng s Plank;
c =3.108 m/s : vn tc nh sng trong chn khng.
+ Cng chm sng t l vi s phtn pht ra trong 1 giy.
+ Phn t, nguyn t, electron pht x hay hp th nh sng, ngha l chng pht x hay hp th phtn.
+ Cc phtn bay dc theo tia sng vi tc c = 3.108 m/s trong chn khng.
+ Nng lng ca mi phtn rt nh. Mt chm sng d yu cng cha rt nhiu phtn do rt nhiu nguyn t, phn t pht ra. V vy ta nhn thy chm sng lin tc.
+Phtn ch tn ti trong trng thi chuyn ng. Khng c phtn ng yn.
d. Gii thch cc nh lut quang in
+ Cng thc Anhxtanh v hin tng quang in: hf =
l
hc
= A +
2
1
mv
2
max
0
.
-vi (0 l gii hn quang in ca kim loi: (0 =
A
hc
-Cng thot ca e ra khi kim loi :
0
.
l
c
h
A
=
-Tn s sng nh sng gii hn quang in :
0
0
l
c
f
=
vi : V0 l vn tc ban u cc i ca quang e (n v ca V0 l m/s)
0
l
l gii hn quang in ca kim loi lm catot (n v ca (0 l m; (m; nm;pm)
m (hay me ) = 9,1.10-31 kg l khi lng ca e; e = 1,6.10-19 C l in tch nguyn t ; 1eV=1,6.10-19J.
+Bng gi tr gii hn quang in
Cht kim loi
(o((m)
Cht kim loi
(o((m)
Cht bn dn
(o((m)
Bc
0,26
Natri
0,50
Ge
1,88
ng
0,30
Kali
0,55
Si
1,11
Km
0,35
Xesi
0,66
PbS
4,14
Nhm
0,36
Canxi
0,75
CdS
0,90
e. Lng tnh sng - ht ca nh sng
+nh sng va c tnh cht sng, va c tnh cht ht. Ta ni nh sng c lng tnh sng - ht.
+Trong mi hin tng quang hc, nh sng thng th hin r mt trong hai tnh cht trn. Khi tnh cht sng th hin r th tnh cht ht li m nht, v ngc li.
+Sng in t c bc sng cng ngn, phtn c nng lng cng ln th tnh cht ht th hin cng r, nh hin tng quang in, kh nng m xuyn, kh nng pht quang,cn tnh cht sng cng m nht.
+Tri li sng in t c bc sng cng di, phtn ng vi n c nng lng cng nh, th tnh cht sng li th hin r hn nh hin tng giao thoa, nhiu x, tn sc, , cn tnh cht ht th m nht.
II. Hin tng quang in trong.
a. Cht quang dn: Cht quang dn l nhng cht bn dn, dn in km khi khng b chiu sng v dn in tt khi b chiu nh sng thch hp.
b. Hin tng quang in trong:Hin tng nh sng gii phng cc electron lin kt chng tr thnh cc electron dn ng thi to ra cc l trng cng tham gia vo qu trnh dn in, gi l hin tng quang in trong.
c. Quang in tr: c ch to da trn hiu ng quang in trong. l mt tm bn dn c gi tr in tr thay i khi cng chm nh sng chiu vo n thch hp.
d. Pin quang in: Pin quang in l ngun in trong quang nng c bin i trc tip thnh in nng. Hot ng ca pin da trn hin tng quang in trong ca mt s cht bn dn ( ng xit, slen, silic,...). Sut in ng ca pin thng c gi tr t 0,5 V n 0,8 V
Pin quang in (pin mt tri) tr thnh ngun cung cp in cho cc vng su vng xa, trn cc v tinh nhn to, con tu v tr, trong cc my o nh sng, my tnh b ti.
III. So snh hin tng quang in ngoi v quang in trong:
So snh
Hin tng quang in ngoi
Hin tng quang dn
Vt liu
Kim loi
Cht bn dn
Bc sng as kch thch
Nh, nng lng ln (nh tia t ngoi)
Va, nng lng trung bnh (as nhn thy..)
Do u im ch cn as kch thch c nng lng nh (bc sng di nh as nhn thy) nn hin tng quang in trong c ng dng trong quang in tr (in tr thay i khi chiu as kch thch, dng trong cc mch iu khin t ng) v pin quang in (bin trc tip quang nng thnh in nng)
IV. Hin tng quangPht quang.
a. S pht quang
+ C mt s cht khi hp th nng lng di mt dng no , th c kh nng pht ra cc bc x in t trong min nh sng nhn thy. Cc hin tng gi l s pht quang.
+ Mi cht pht quang c mt quang ph c trng cho n.
b.Hunh quang v ln quang- So snh hin tng hunh quang v ln quang:
So snh
Hin tng hunh quang
Hin tng ln quang
Vt liu pht quang
Cht kh hoc cht lng
Cht rn
Thi gian pht quang
Rt ngn, tt rt nhanh sau khi tt as kch thch
Ko di mt khong thi gian sau khi tt as kch thch (vi phn ngn giy n vi gi, ty cht)
c im - ng dng
As hunh quang lun c bc sng di hn as kch thch (nng lng b hn - tn s nh hn) . Dng trong n ng
Bin bo giao thng, ...
c. nh lut Xtc v s pht quang( c im ca nh sng hunh quang )
nh sng pht quang c bc sng (hq di hn bc sng ca nh sng kch thch (kt:
hf hq < hfkt => (hq > (kt.
d.ng dng ca hin tng pht quang:S dng trong cc n ng thp sng, trong cc mn hnh ca dao ng k in t, tivi, my tnh. S dng sn pht quang qut trn cc bin bo giao thng.
V. Mu nguyn t Bo.
a. Mu nguyn t ca Bo +Tin v trng thi dng
-Nguyn t ch tn ti trong mt s trng thi c nng lng xc nh En, gi l cc trng thi dng. Khi trng thi dng, nguyn t khng bc x.
-Trong cc trng thi dng ca nguyn t, electron chuyn ng quanh ht nhn trn nhng qu o c bn knh hon ton xc nh gi l qu o dng.
-Cng thc tnh qu o dng ca electron trong nguyn t hyr: rn = n2r0, vi n l s nguyn v
r0 = 5,3.10-11 m, gi l bn knh Bo (lc e qu o K)
Trng thi dng n
1
2
3
4
5
6
Tn qu o dng
K
L
M
N
O
P
Bn knh: rn = n2r0
r0
4r0
9r0
16r0
25r0
36r0
Nng lng e Hidro:
2
13,6
()
n
EeV
n
=-
2
13,6
1
-
2
13,6
2
-
2
13,6
3
-
2
13,6
4
-
2
13,6
5
-
2
13,6
6
-
Nng lng electron trong nguyn t hir:
2
13,6
()
n
EeV
n
=-
Vi n ( N*.
-Bnh thng, nguyn t trng thi dng c nng lng thp nht gi l trng thi c bn. Khi hp th nng lng th nguyn t chuyn ln trng thi dng c nng lng cao hn, gi l trng thi kch thch. Thi gian nguyn t trng thi kch thch rt ngn (c 10-8 s). Sau nguyn t chuyn v trng thi dng c nng lng thp hn v cui cng v trng thi c bn.
+ Tin v s bc x v hp th nng lng ca nguyn t
-Khi nguyn t chuyn t trng thi dng c nng lng En sang trng thi dng c nng lng Em nh hn th nguyn t pht ra mt phtn c nng lng: ( = hfnm = En Em.
-Ngc li, nu nguyn t trng thi dng c nng lng Em m hp th c mt phtn c nng lng hf ng bng hiu En Em th n chuyn sang trng thi dng c nng lng En ln hn.
1
hc
l
-S chuyn t trng thi dng Em sang trng thi dng En ng vi s nhy ca electron t qu o dng c bn knh rm sang qu o dng c bn knh rn v ngc li.
b. Quang ph pht x v hp th ca nguyn t hidr
-Nguyn t hir c cc trng thi dng khc nhau EK, EL, EM, ... .
Khi electron chuyn ng trn cc qu o dng K, L, M, ...
-Khi electron chuyn t mc nng lng cao (Ecao) xung mc nng
lng thp hn (Ethp) th n pht ra mt phtn c nng lng xc nh: hf = Ecao Ethp.
-Mi phtn c tn s f ng vi mt sng nh sng n sc c bc sng ( =
f
c
, tc l mt vch quang ph c mt mu (hay mt v tr) nht nh. iu l gii quang ph pht x ca hir l quang ph vch.
-Ngc li nu mt nguyn t hir ang mt mc nng lng Ethp no m nm trong mt chm nh sng trng, trong c tt c cc phtn c nng lng t ln n nh khc nhau, th lp tc nguyn t s hp th mt phtn c nng lng ph hp ( = Ecao Ethp chuyn ln mc nng lng Ecao. Nh vy, mt sng nh sng n sc b hp th, lm cho trn quang ph lin tc xut hin mt vch ti. Do quang ph hp th ca nguyn t hir cng l quang ph vch.
VI. S lc v laze.
Laze l mt ngun sng pht ra mt chm sng cng ln da trn vic ng dng hin tng pht x cm ng.
a.. c im ca laze
+ Laze c tnh n sc rt cao.
+ Tia laze l chm sng kt hp (cc phtn trong chm c cng tn s v cng pha).
+ Tia laze l chm sng song song (c tnh nh hng cao).
+ Tia laze c cng ln. V d: laze rubi (hng ngc) c cng ti 106 W/cm2.
b. Mt s ng dng ca laze
+ Tia laze c dng nh dao m trong phu thut mt, cha mt s bnh ngoi da (nh tc dng nhit), .
+ Tia laze dng truyn thng thng tin bng cp quang, v tuyn nh v, iu khin con tu v tr, ...
+ Tia laze dng trong cc u c a CD, bt ch bng, bn , th nghim quang hc trng ph thng, ...
+ Tia laze c dng trong o c , ngm ng thng ...
+ Ngoi ra tia laze cn c dng khoan, ct, ti, ...chnh xc cc vt liu trong cng nghip.
B. CC DNG BI TP
I. HIN TNG QUANG IN:
1. Cc cng thc:
+Nng lng ca phtn nh sng: ( = hf . Trong chn khng: ( =
l
hc
.
+Cng thc Anhxtanh: hf =
l
hc
= A +
2
1
mv
2
max
0
=
0
l
hc
+ Wdmax;
+Gii hn quang in : (0 =
A
hc
; Cng thot ca e ra khi kim loi :
0
.
l
c
h
A
=
v0Max l vn tc ban u ca electron quang in khi thot khi catt
f, ( l tn s, bc sng ca nh sng kch thch
+ dng quang in trit tiu th UAK ( Uh (Uh < 0):
2
0ax
2
M
h
mv
eU
=
Uh gi l hiu in th hm
Lu : Trong mt s bi ton ngi ta ly Uh > 0 th l ln.
+ Xt vt c lp v in, c in th cc i VMax v khong cch cc i dMax m electron chuyn ng trong in trng cn c cng E c tnh theo cng thc:
2
ax0axax
1
2
MMM
eVmveEd
==
+ Vi U l hiu in th gia anot v catot, vA l vn tc cc i ca electron khi p vo ant, vK = v0Max l vn tc ban u cc i ca electron khi ri catt th:
22
11
22
AK
eUmvmv
=-
+S ht photn p vo:
ptpt
N==
hc
+Cng sut ca ngun sng:
e
l
n
P
=
l
n
l s photon pht ra trong mi giy.
e
l lng t nh sng.
+Cng dng quang in bo ha:
e
n
I
e
bh
=
(Gi s n= ne , vi n l s electron n c Ant)
e
n
l s quang electron bc ra khi catot mi giy = n s electron ti anot mi giy
e
l in tch nguyn t.
+Hiu in th hm:
2
0
1
//
2
he
eUmv
=
+Hiu sut lng t:
l
n
n
H
e
=
Hay :
bh
Ihc
H=
p
e
e
n
l s electron bc ra khi catot kim loi mi giy.
l
n
l s photon p vo catot trong mi giy.
2. Cc HNG S Vt L v I N V Vt L :
+Hng s Plank: h = 6,625.10-34 J.s
+Vn tc nh sng trong chn khng: c = 3.108 m/s
+in tch nguyn t : |e| = 1,6.10-19 C; hay e = 1,6.10-19 C
+Khi lng ca e : m (hay me ) = 9,1.10-31 kg
+i n v: 1eV=1,6.10-19J. 1MeV=1,6.10-13J.
+Cc hng s c ci sn trong my tinh cm tay Fx570MS; Fx570ES; 570ES Plus bng cc lnh:
[CONST] Number [0 (40] ( xem cc m lnh trn np ca my tnh cm tay ) .
Lu : Khi tnh ton dng my tnh cm tay, ty theo yu cu bi c th nhp trc tip cc hng s t bi cho, hoc nu mun kt qu chnh xc hn th nn nhp cc hng s thng qua cc m lnh CONST [0( 40] c ci t sn trong my tinh! (Xem thm bng HNG S VT L di y)
Bng Cc hng s vt l :
Hng s vt l
M s
Cch nhp my :
570MS bm: CONST 0( 40 =
570ES bm: SHIFT 7 0( 40 =
Gi tr hin th
Khi lng prton (mp)
01
Const [01] =
1,67262158.10-27 (kg)
Khi lng ntron (mn)
02
Const [02] =
1,67492716.10-27 (kg)
Khi lng lectron (me)
03
Const [03] =
9,10938188.10-31 (kg)
Bn knh Bo (a0)
05
Const [05] =
5,291772083.10-11 (m)
Hng s Plng (h)
06
Const [06] =
6,62606876.10-34 (Js)
Khi lng 1u (u)
17
Const [17] =
1,66053873.10-27 (kg)
in tch lectron (e)
23
Const [23] =
1,602176462.10-19 (C)
S Avgar (NA)
24
Const [24] =
6,02214199.1023 (mol-1)
Hng s Bnzman (k)
25
Const [25] =
1,3806503.10-23 (SI)
Th tch mol kh iu kin tiu chun (Vm)
26
Const [26] =
0,022413996 (m3)
Hng s kh l tng (R)
27
Const [27] =
8,314472 (J/mol.K)
Tc nh sng trong chn khng (C0) hay c
28
Const [28] =
299792458 (m/s)
Gia tc trng trng ti mt t (g)
35
Const [35] =
9,80665 (m/s2)
Hng s Rydberg RH (R()
16
Const [16] =
1,097373157.10 7 (m-1)
Hng s hp dn (G)
39
Const [39] =
6,673.10-11 (Nm2/kg2)
-V d1: My 570ES:
Cc hng s
Thao tc bm my Fx 570ES
Kt qu hin th mn hnh
Ghi ch
Hng s Plng (h)
SHIFT 7 CONST 06 =
6.62606876 .10-34 J.s
Tc nh sng trong chn khng (C0) hay c
SHIFT 7 CONST 28 =
299792458 m/s
in tch lectron (e)
SHIFT 7 CONST 23 =
1.602176462 10-19 C
Khi lng lectron (me)
SHIFT 7 CONST 03 =
9.10938188 .10-31 Kg
Hng s Rydberg RH (R()
SHIFT 7 CONST 16 =
1,097373157.10 7 (m-1)
b. i n v ( khng cn thit lm):Vi cc m lnh ta c th tra bng in np ca my tnh.
- My 570ES bm Shift 8 Conv [m s] =
-V d 2: T 36 km/h sang ? m/s , bm: 36 Shift 8 [Conv] 19 = Mn hnh hin th : 10m/s
My 570MS bm Shift Const Conv [m s] =
3. Cc dng bi tp: Cho 1 eV = 1,6.10-19 J ; h = 6,625.10-34 Js ; c = 3.108 m/s; me = 9,1.10-31 kg.
Dng 1: Tnh gii hn quang in, cng thot v vn tc cc i ban u ca e quang in khi bt ra khi Katot.
a.PPG: -Gii hn quang in: (0 =
A
hc
; Cng thot
0
.
l
c
h
A
=
; A: J hoc eV; 1eV =1,6.10-19 J
-Phng trnh Anhxtanh:hf =
l
hc
= A +
2
1
mv
2
max
0
-ng nng cc i:
max
0
11
()
d
Whc
ll
=-
2
0
0
1
2
hchc
mv
ll
=+
=>
0
0
211
()
e
hc
v
m
ll
=-
-Cc hng s :
34819
6,625.10;3.10/;1,6.10
hcmseC
--
===
;
31
9,1.10
e
mkg
-
=
b.Cc V d :
V d 1: Gii hn quang in ca km l (o = 0,35(m. Tnh cng thot ca lectron khi km?
HD gii: T cng thc:
0
hchc
A
0
A
l
l
==>=
348
6,625.10.3.10
6
0,35.10
-
=
-
=5,67857.10-19 J =3,549eV
Bm my tnh: phn s
SHIFT 7 06 h X SHIFT 7 28 Co ( 0,35 X10x -6 = 5.6755584x10-19J
i sang eV: Chia tip cho e: Bm ( SHIFT 7 23 = Hin th: 3,5424 eV
Nhn xt: Hai kt qu trn khc nhau l do thao tc cch nhp cc hng s !!!
V d 2: (TN-2008): Gii hn quang in ca ng (Cu) l 0 = 0,30 m. Bit hng s h = 6,625.10-34 J.s v vn tc truyn nh sng trong chn khng c = 3.108 m/s. Cng thot ca lectrn khi b mt ca ng l
A.6,625.10-19 J. B. 6,265.10-19 J. C. 8,526.10-19 J. D. 8,625.10-19 J.
V d 3: Gi hn quang in ca Ge l (o = 1,88(m. Tnh nng lng kch hat (nng lng cn thit gii phng mt lectron lin kt thnh lectron dn) ca Ge?
V d 4: Mt kim loi c cng thot l 2,5eV. Tnh gii hn quang in ca kim loi :
A. 0,4969
m
m B. 0,649
m
m C. 0,325
m
m D. 0,229
m
m
V d 5: Gii hn quang in ca KL dng lm Kotot l 0,66(m. Tnh:
1. Cng thot ca KL dng lm K theo n v J v eV.
2. Tnh ng nng cc i ban u v vn tc cc i ca e quang in khi bt ra khi K, bit nh sng chiu vo c bc sng l 0,5(m .
V d 6: Catt ca mt t bo quang in c cng thot bng 3,5eV.
a. Tm tn s gii hn v gii hn quang in ca kim loi y.
b. Khi chiu vo catt mt bc x c bc sng 250 nm c xy ra hin tng quang in khng?
-Tm hiu in th gia A v K dng quang in bng 0.
-Tm ng nng ban u cc i ca cc lectron quang in.
-Tm vn tc ca cc lectron quang in khi bt ra khi K.
5.Trc nghim:Cu 1.Cng thot electron ca mt kim loi l A = 4eV . Gii hn quang in ca kim loi ny l :A. 0,28 m B. 0,31 (m C. 0,35 (m D. 0,25 (m
Cu 2.Gii hn quang in ca canxi l (0 = 0,45(m th cng thot electron ra khi b mt canxi l :A. 5,51.10-19J B. 3,12.10-19J C. 4,41.10-19J D. 4,5.10-19JCu 3.Mt t bo quang in c catt bng Na , cng thot electron ca Na bng 2,1 eV . Gii hn quang in ca NaA. 0,49 (m B. 0,55 (m C. 0,59 (m D. 0,65 (mCu 4. Gii hn quang in ca niken l 248nm, th cng thot ca lectron khi niken l bao nhiu ?A. 5 eV B. 50 eV C. 5,5 eV D. 0,5 eVCu 5. Catt ca t bo quang in lm bng vnfram. Bit cng thot lectron i vi vnfram l 7,2.10-19 J. Gii hnquang in ca vnfram l bao nhiu ?A. 0,276 m. B. 0,375 m. C. 0,425 m. D. 0,475 m.Cu 6.Nng lng phton ca tia Rnghen c bc sng 0,05 l :A. 39,72.10-15J B. 49,7.10-15J C. 42.10-15J D. 45,67.10-15JCu 7 : Trong chn khng, bc x n sc vng c bc sng l 0,589 (m. Ly h = 6,625.10-34J.s; c=3.108 m/s v e =1,6.10-19 C. Nng lng ca phtn ng vi bc x ny c gi tr lA. 2,11 eV. C. 4,22 eV. C. 0,42 eV. D. 0,21 eV.
DNG 2: Tm ng nng (vn tc)cc i ca electron khi xy ra hin tng quang in:
HD Gii : C a. Phng Php Gai : So snh bc sng vi gii hn 0+Nu0hoc f f0 (C xy ra HTQ+ Nu > 0 hoc f < f0 (Khng xy ra HTQCh :1.Nu cho v A (phi tm 0 ri so snh bc sng vi gii hn 02.Nu cho tn s f v A(phi tm f0 ( hoc tm ) v tm 0 ri so snh s f v f0.ng thc:
2
0ax
2
M
mv
hc
hfA
e
l
===+
vi
2
ax
2
m
mv
E
=
t suy ra E. Lu : 1eV=1,6.10-19J
V d 1: Catt ca t bo quang in lm bng vnfram, bit cng thot ca electron vi vnfram l 7,2.10-19J. Chiu vo catt nh sng c bc sng
0,18
m
lm
=
. ng nng cc i ca lectrn khi bc ra khi catt l bao nhiu?
M rng: bi ton tng t tm Vmax ta cng tm Emax ...
V d 2: Chiu ln lt hai bc x c bc sng
1
l
= 600nm v
2
l
= 0,3
m
m
vo mt tm kim loi th nhn c cc quang e c vn tc cc i ln lt l v1 = 2.105 m/s v v2 = 4.105 m/s.Chiu bng bc x c bc sng
3
l
= 0,2
m
m th vn tc cc i ca quang in t l
A. 5.105 m/s B . 2
7
.105 m/s C.
6
.105 m/s D.6.105 m/s
Bi 1: Catt ca mt t bo quang in c cng thot bng 3,5eV.a. Tm tn s gii hn v gii hn quang in ca kim loi y.b. Bi 2: Cng thot lectron ca mt kim loi l 7,64.1019 J. Chiu ln lt vo b mt tm kim loi ny cc bc x cbc sng l 1 = 0,18 m, 2 = 0,21 m v 3 = 0,35 m. Ly h = 6,625.10-34 J.s, c = 3.108 m/s. Bc x no gy chin tng quang in i vi kim loi ?A. C ba bc x (1, (3). B. Khng c bc x no trong ba bc x trn.C. Hai bc x (1 v 2).
D. Ch c bc x 1. Khi chiu vo catt mt bc x c bc sng 250 nm c xy ra hin tng quang in khng?
c. Trc nghim:Cu 1(TN-2009): Chiu mt chm bc x c bc sng vo b mt mt tm nhm c gii hn quang in 0,36m.Hin tng quang in khng xy ra nu bngA. 0,24 m. B. 0,42 m C. 0,30 m. D. 0,28 m.Cu 2: Chiu mt chm bc x n sc vo mt tm km c gii hn quang in 0,35m. Hin tng quang in skhng xy ra khi chm bc x c bc sng :A. 0,1 m B. 0,2 m C. 0,3 m D. 0,4 mCu 3: Ln lt chiu hai bc x c bc sng ((((t tm km c gii hn quang in((c x no gy ra hin tng quang in?A. Ch c bc x (2. B. Ch c bc x ( hai bc x. D. Khng c bc x no trong hai bc x trn.Cu 4: Mt cht quang dn c gii hn quang dn 0,62(m. Chiu vo bn dn ln lt cc chm bc x n sc ctn s f1= 4,5.1014Hz; f2= 5,0.1013Hz; f3 = 6,5.1013Hz; f4 = 6,0.1014Hz th hin tng quang dn s xy ra viA. Chm bc x 1; B. Chm bc x 2 C. Chm bc x 3; D. Chm bc x 4Cu 5: Chiu mt chm bc x c tn s song f1 = 9,5 .1014 Hz; f2 = 8,5 .1014 Hz; f3 = 9 .1014 Hz; f4 = 7,0 1014 Hz vo b mt mt tm nhm c gii hn quang in 0,36m. Hin tng quang in khng xy ra viA. Chm bc x 1. B. Chm bc x 2. C. Chm bc x 3. D. Chm bc x 4.Cu 6: Mt cht quang dn c gii hn quang dn l 0,62(m . Chiu vo cht bn dn ln lt cc chm bc xn sc c tn s f1 = 4,5 .1014 Hz; f2 = 5 .1014 Hz; f3 = 5,5 .1014 Hz; f4 = 6,0 1014 Hz; th hin tng quang dn sxy ra viA. Chm bc x 1. B. Chm bc x 2. C. Chm bc x 3. D. Chm bc x 4.Cu 7: Mt kim loi c cng thot lectron l 6,02.1019 J. Chiu ln lt vo kim loi ny cc bc x c bc sng= 0,18 m, = 0,21 m, = 0,32 m v = 0,35 m. Nhng bc x c th gy ra hin tng quang in kimloi ny c bc sng l 2 v 3. B. ch c 1 v 2. C. ch c 3 v 4. D. 2, 3 v 4.Cu 8: Mt cht KIM LOI c gii hn quang in l 0,5(m . Chiu vo cht kim loi ln lt cc chm bc xn sc c nng lng 1 = 1,5 .10 -19 J; 2 = 2,5 .10-19 J; 3 = 3,5 .10-19 Hz; 4 = 4,5. 10-19 J th hin tng quang ins xy ra viA. Chm bc x 1. B. Chm bc x 2. C. Chm bc x 3. D
DNG 3: Tm hiu in th hm khng electron v anot (hay dng quang in trit tiu)
HD Gii :
- Hin tng cc electron khng v c anot do in trng sinh cng cn cn tr chng.
- Mun vy th: Cng cn in trng c gi tr b nht bng ng nng ban u cc i ca cc electron quang in. Ta c:
2
0ax
2
M
h
mv
eU
=
suy ra: Uh=
|
|
2
2
0
e
mv
-Lu : Khi chn kt qu th Uh
0
11
()
h
hc
U
e
ll
=-
V d 1: Ta chiu nh sng c bc sng0,42 (m vo K ca mt tbq. Cng thot ca KL lm K l 2eV. trit tiu dng quang in th phi duy tr mt hiu in th hmUAK bng bao nhiu?
V d 2: Chiu chm bc x in t c tn s f = 5,76.1014 Hz vo mt ming kim loi th cc quang electron c vn tc ban u cc i l v = 0,4.106 m/s. Tnh cng thot electron v bc sng gii hn quang in ca kim loi .
V d 3: Cng thot electron khi kim loi natri l 2,48 eV. Mt t bo quang in c catt lm bng natri, khi c chiu sng bng chm bc x c ( = 0,36 (m th cho mt dng quang in c cng bo ha l 3(A. Tnh vn tc ban u cc i ca electron quang in v s electron bt ra khi catt trong 1 giy.
V d 4: Chiu bc x c bc sng ( = 0,438 (m vo catt ca mt t bo quang in. Bit kim loi lm catt ca t bo quang in c gii hn quang in l (0 = 0,62 (m. Tm in p hm lm trit tiu dng quang in.
V d 5: Chiu mt bc x in t c bc sng ( vo catt ca mt t bo quang in. Bit cng thot electron ca kim loi lm catt l 3eV v cc electron bn ra vi vn tc ban u cc i l 7.105 m/s. Xc nh bc sng ca bc x in t v cho bit bc x in t thuc vng no trong thang sng in t.
V d 6: Chiu bc x c bc sng 0,405(m vo mt tm kim loi th cc quang electron c vn tc ban u cc i l v1. Thay bc x khc c tn s 16.1014 Hz th vn tc ban u cc i ca cc quang electron l v2 = 2v1. Tm cng thot electron ca kim loi.
V d 7: Chiu bc x c bc sng ( = 0,4 (m vo catt ca mt t bo quang in. Bit cng thot electron ca kim loi lm catt l A = 2 eV, in p gia ant v catt l UAK = 5 V. Tnh ng nng cc i ca cc quang electron khi ti ant.
.
V d 8: Catot ca t bo quang in lm bng ng, cng thot khi ng l 4,47eV.
Cho bit: h = 6,625.10-34 (J.s) ; c = 3.108 (m/s) ; e = 1,6.10-19 (C).
a. Tnh gii hn quang in ca ng.
b. Chiu ng thi 2 bc x in t c bc sng 1 = 0,210 (m) v 2 = 0,320 (m) vo catot ca t bo quang in trn, phi t hiu th hm bng bao nhiu trit tiu hon ton dng quang in.
V d 9: Ln lt chiu vo catt ca mt t bo quang in hai bc x n sc c bc sng
m
m
l
6
,
0
1
=
v
m
m
l
5
,
0
2
=
th hiu in th hm dng quang in trit tiu khc nhau ba ln. Gii hn quang in ca kim loi lm catt l:
A.
).
(
745
,
0
m
m
B.
).
(
723
,
0
m
m
C.
).
(
667
,
0
m
m
D.
).
(
689
,
0
m
m
V d 10: Chiu bc x c bc sng1=276nm vo catot ca mt t bo quang in lm bng nhm th hiu in th hm trit tiu dng quang in l 1,05V. Thay bc x trn bng bc x 2=248nm v catot gi lm bng ng th hiu in th hm trit tiu dng quang in gi l 0,86V. Vy khi chiu ng thi c hai bc x 1 v 2 vo catot gi l hp kim ng v nhm th hiu in th hm trit tiu dng quang in l
A. 1,05V B. 1,55V C. 0,86V D. 1,91V
V d 11: Chiu bc x c bc sng = 0,25m vo catod ca mt t bo quang in cn mt hiu in th hm U = 3V trit tiu dng quang in. Chiu ng thi v = 0,15m th hiu in th hm khi l bao nhiu ?
3.Trc nghim:
Cu 1. Chn p n ng.Catt ca mt t bo quang in lm bng vnfram .Bit cng thot ca electrn i vivnfram l 7,2. 10-19J v bc sng nh sng kch thch l ((m. trit tiu hon ton dng quang in, phit vo hai u ant v catt mt hiu in th hm bng bao nhiu ?A.Uh = 6,62 V ; B.Uh = 2,5 V C.Uh = 4,5 V D.Uh = 2,4 VCu 2. Mt t bo quang in c catt bng Na, cng thot ca electron ca Na bng 2,1eV. Chiu vo t bo quangin bc x n sc c bc sng 0,42( s ca hiu in th hm lA. 0,86V B. 2,95V C. 1,17V D. kt qu kh
Dng 5: Cho UAK> 0 hy tnh vn tc ca e khi p vo Anot.
PPG: Gi v l vn tc ca e khi p vo Anot. p dng nh l ng nng:
22
0
11
22
AK
mvmveU
-=
=>
22
0
11
22
AK
mvmveU
=+
=>
2
1
2
AK
mvAeU
e
=+-+
2
0
111
()
2
AK
mvhceU
ll
=-+
=> v ....
V d 1:
V d 2: Katt ca t bo quang in c cng thot 1,5eV, c chiu bi bc x n sc (. Ln lt t vo t bo, in pUAK = 3V v UAK = 15V, th thy vn tc cc i ca elctrn khi p vo ant tng gp i. Gi tr ca ( l:A. 0,259 (m. B. 0,795(m. C. 0,497(m. D. 0,211(m.
Bi 1: Katt ca t bo quang in c cng thot 2,07 eV, c chiu bi bc x n sc (m vo t bo boquang in vi in p UAK = 1 kV .Tnh vn tc cc i ca elctrn khi p vo ant.
Bi 2: Katt ca t bo quang in c cng thot 1,5eV, c chiu bi bc x n sc (Ln lt t vo t bo,in pUAK = 3V v U AK = 15V, th thy vn tc cc i ca elctrn khi p vo ant tng gp i. Gi tr ca (A. 0,259 (m. B. 0,795(m. C. 0,497(m. D. 0,211(m.
Bi 3: Chiu bc x c bc sng vo catot ca t bo quang in.dng quang in b trit tiu khi UAk - 4,1V.khi UAK =5V th vn tc cc i ca electron khi p vo anot l:A. 1,789.106m/s B. 1,789.105m/s C. 1,789.105 km/s B. 1,789.104 km/s
Bi 4: Hiu in th hiu dng gia anot v catot ca mt ng culitgio l 10kV. B qua ng nng ca cc electronkhi bt khi catot. Tnh tc cc i ca cc electron p vo anot.
3.Trc nghim:Cu 1.Cho gii hn quang in ca catot l (= 660 nm v t vo gia Anot v Catot mt UAK = 1,5 V. Dng bcx c (330 nm. ng nng cc i ca cc quang electron khi p vo anot l:A. 3,01.10-19J. B. 4.10-20J. C. 5.10-20J. D. 5,41.10-19J.Cu 2.Chiu nh sng n sc c bc sng ( mt ca tt ca mt t bo quang in, hiu in thhm ca n c gi tr l Uh. Cho gii hn quang in ca catot l (= 660 nm v t vo gia Anot v Catot mt htUAK = 1,5 V. Tnh ng nng cc i ca cc quang electron khi p vo anot nu dng bc x ( = 282,5 nm :A. 5,41.10-19J. B. 6,42.10-19J. C. 3,05.10-19J. D. 7,47.10-19J.Cu 3. Khi chiu chm bc x =0,2m rt hp vo tm ca catt phng ca mt t bo quang in cng thot electronl 1,17.10-19J. Ant ca t bo quang in cng c dng bn phng song song vi catt. t vo gia ant v catt mthiu in th UAK = -2V th vn tc cc i ca electron khi n ant bngA. 1,11.106m/s B. 1,22.1011m/s C. 1,62.106m/s D. 2,62.1012m/s
Dng 6: Cho cng sut ca ngun bc x. Tnh s Phton p vo Katot sau thi gian t
PPG: Nng lng ca chm photon ri vo Katot sau khong thi gian t: W = P.t
-S photon p vo Katot khong thi gian t:
..
.
WPt
N
hc
l
l
e
==
-Cng sut ca ngun : P = n.. (n l s photon tng ng vi bc x pht ra trong 1 giy).
-Cng dng in bo ho : Ibh = ne.e .(ne l s electron quang in t catot n anot trong 1 giy).
-Hiu sut quang in : H =
l
n
n
e
V d 1: Mt ngn n pht ra nh sng n sc c (=0,6(m s pht ra bao nhiu photon trong 10s nu cng sut n l P = 10W.
V d 2: Ngun Laser mnh pht ra nhng xung bc x c nng lng
3000
WJ
=
. Bc x pht ra c bc sng
nm
480
=
l
. Tnh s photon trong mi bc x ?
Bi 1: Chiu vo catt mt nh sng c bc sng 0,546m, th dng quang in bo ho c gi tr l 2mA. Cng sutbc x l 1,515W . Hiu sut lng t l bao nhiu ?.
Bi 2: Chiu vo catt mt nh sng c bc sng 0,546m, th dng quang in bo ho c gi tr l 2mA. Cng sutbc x l 1,515W . Hiu sut lng t l bao nhiu ?.
DNG 7: Tm s electron bay ra khi anot, s photon p vo anot trong mt thi gian t bt k. Tm hiu sut quang in.
PPG: Hiu sut lng t ca t bo quang in l i lng c tnh bng t s gia s e quang in bt ra khi Katot vi s photon p vo Katot.
H =
l
n
n
e
=>
.
.
..
bh
bh
It
Ihc
e
H
Pt
eP
hc
l
l
==
.
HD Gii :
-Tm s electron bay ra khi catot l s electron to ra dng quang in do vy ta vn dng cng thc: I=q/t=ne|e|/t t suy ra ne
-Tm s photon p vo anot: Ta tm nng lng ca chm photon v ly nng lng ca chm photon chia cho nng lng ca mt photon th ta c s photon cn tm. Vi bi ton ny thng cho cng sut bc x P nn ta c: np=Ap/
e
=P.t/hf.
- Mun tm hin sut quang in ta dng cng thc: H=ne/np
V d 1: : Chiu mt chm bc x vo t bo quang in c catot lm bng Na th cng dng quang in bo ha l 3
A
m
. S electron b bt ra ra khi catot trong hai pht l bao nhiu?
HD Gii: p dng cng thc I=q/t=ne|e|/t ta suy ra c ne=I.t/|e|. Lu i n v ca I ra ampe
V d 2: Chiu vo catt mt nh sng c bc sng 0,546m, th dng quang in bo ho c gi tr l 2mA. Cng sut bc x l 1,515W . Hiu sut lng t l bao nhiu ?.
V d 3: Khi chiu 1 bc x in t c bc sng 0,5 micromet vo b mt ca t bo quang in to ra dng in bo ha l 0,32A. Cng sut bc x p vo Katot l P=1,5W. tnh hiu sut ca t bo quang in.
V d 4: Cng thot ca lectron i vi Natri l 2,48 (eV). Catot ca t bo quang in lm bng Natri c chiu sng bi bc x c bc sng = 0,36 (m) th c dng quang in bo ho Ibh = 50 (mA).Cho bit:h = 6,625.10-34 (J.s); c = 3.10 (m/s) ; me = 9,1.10-31 (kg); - e = - 1,6.10-19 (C).
a) Tnh gii hn quang in ca Natri.
b) Tnh vn tc ban u cc i ca lectron quang in.
c) Hiu sut quang in bng 60%, tnh cng sut ca ngun bc x chiu vo catt.
V d 5: Cht lng fluorexein hp th nh sng kch thch c bc sng = 0,48m v pht ra nh c bc sng = 0,64m. Bit hiu sut ca s pht quang ny l 90% (hiu sut ca s pht quang l t s gia nng lng ca nh sng pht quang v nng lng ca nh sng kch thch trong mt n v thi gian), s phtn ca nh sng kch thch chiu n trong 1s l 2012.1010 ht. S phtn ca chm sng pht quang pht ra trong 1s l
A. 2,6827.1012B. 2,4144.1013C. 1,3581.1013D. 2,9807.1011
3.Trc nghim:Cu 1. Mt n laze c cng sut pht sng 1W pht nh sng n sc c bc sng 0,7(m/s. S phtn ca n pht ra trong 1 giy l:A. 3,52.1019. B. 3,52.1020. C. 3,52.1018. D. 3,52.1016.Cu 3. Mt ngun pht ra nh sng c bc sng 662,5 nm vi cng sut pht sng l 1,5.10-4 W. Ly h = 6,625.10-34J.s; c = 3.108 m/s. S phtn c ngun pht ra trong 1 s lA. 5.1014. B. 6.1014. C. 4.1014. D. 3.1014.Cu 4. Cng thot ca kim loi Na l 2,48eV. Chiu mt chm bc x c bc sng 0,36 m vo t bo quang in ccatt lm bng Na th cng dng quang in bo ha l 3 A th. Nu hiu sut lng t (t s electron bt ra tcatt v s photon n p vo catt trong mt n v thi gian) l 50% th cng sut ca chm bc x chiu vo cattlA. 35,5.10-5W B. 20,7.10-5W C. 35,5.10-6W D. 20,7.10-6WCu 5.Chiu nh sng n sc c bc sng ( mt ca tt ca mt t bo quang in, c Ibh = 2 mA.Cng sut pht x l P = 1,515 W. Tnh hiu sut lng t.A. 30,03.10-2%. B. 42,25.10-2%. C. 51,56.10-2%. D. 62,25.10-2%.Cu 6. Chiu chm nh sng c cng sut 3 W, bc sng 0,35 (m vo catt ca t bo quang in c cng thotelectron 2,48 eV th o c cng dng quang in bo ho l 0,02 A. Tnh hiu sut lng t.A. 0,2366%. B. 2,366%. C. 3,258%. D. 2,538%.Cu 7. Mt t bo quang in c catt c lm bng asen c cng thot electron 5,15 eV. Chiu vo catt chm bcx in t c bc sng 0,2 (i t bo quang in vi ngun in mt chiu. Mi giy catt nhn c nnglng ca chm sng l 0,3 mJ, th cng dng quang in bo ho l 4,5.10-6 A. Hiu sut lng t lA. 9,4%. B. 0,094%. C. 0,94%. D. 0,186%.Cu 8.Cng dng quang in bo ho l 40 ( th s electron b bt ra khi b mt quang in n c Anottrong 1 giy l:A. 25.1013. B. 25.1014. C. 50.1012. D. 5.1012.Cu 9.Chiu nh sng n sc c bc sng 0,30m vo mt cht th thy cht pht ra nh sng c bc sng0,50m. Cho rng cng sut ca chm sng pht quang ch bng 1,5% cng sut ca chm sng kch thch. Hy tnhxem trung bnh mi phtn nh sng pht quang ng vi bao nhiu phtn nh sng kch thch.A. 60. B. 40. C. 120. D. 80.Cu 10:Mt cht c kh nng pht ra bc x c bc sng 0,5m khi b chiu sng bi bc x 0,3m. Bit rng cngsut ca chm sng pht quang ch bng 0,01 cng sut ca chm sng kch thch v cng sut chm sng kch thch l1W. Hy tnh s photon m cht pht ra trong 10s.A. 2,516.1017 B. 2,516.1015 C. 1,51.1019 D. 1,546.1015.Cu 11: Dung dch Fluorxin hp th nh sng c bc sng 0,49m v pht ra nh sng c bc sng 0,52m, ngita gi hiu sut ca s pht quang l t s gia nng lng nh sng pht quang v nng lng nh sng hp th. Bithiu sut ca s pht quang ca dung dch Fluorxin l 75%. S phn trm ca phtn b hp th dn n s phtquang ca dung dch l:A. 82,7% B. 79,6% C. 75,0%
Dng 8: Cho cng dng quang in bo ho. Tnh s e quang in bt ra khi Katot sau khong thi gian t.
PPG: in lng chuyn t K ( A : q= Ibh.t = ne.e.t =>
..
..
bhbh
e
ItI
q
n
etete
===
Gi ne l s e quang in bt ra Kaot ( ne ( n( );
Gi n l s e quang n c Ant ( n ( ne , Khi I = Ibh. Th n = ne )
Lu : Nu khng cho r % e quang in bt ra v c Anot th lc ta c th cho n= ne = n(
V d 1: Cho cng dng quang in bo bo l 0,32mA. Tnh s e tch ra khi Katot ca t bo quang in trong thi gian 20s bit ch 80% s e tch ra v c Anot.
V d 2: Mt t bo quang in c catt lm bng Asen c cng thot electron bng 5,15 eV. Chiu chm sng n sc c bc sng 0,20 (m vo catt ca t bo quang in th thy cng dng quang in bo ha l 4,5 (A. Bit cng sut chm bc x l 3 mW . Xc nh vn tc cc i ca electron khi n va b bt ra khi catt v hiu sut lng t.
V d 3: Ngun sng th nht c cng sut P1 pht ra nh sng n sc c bc sng
1
450
nm
l
=
. Ngun sng th hai c cng sut P2 pht ra nh sng n sc c bc sng
2
0,60
m
lm
=
. Trong cng mt khong thi gian, t s gia s photon m ngun th nht pht ra so vi s photon m ngun th hai pht ra l 3:1. T s P1 v P2 l:
A. 4.B. 9/4C. 4/3.D. 3.
V d 4: Catt ca mt t bo quang in lm bng Cs l kim koi c cng thot A = 2eV,c chiu bc x c bc sng ( = 0,3975(m . Bit cng dong quang in bo ha Io = 2(A v hiu sut quang in H= 0,5 Tnh s phntn ti catt trong 1s l bao nhiu
Dng 9: ng dng ca hin tng quang in tnh cc hng s h, e, A.
p dng cc cng thc:
- Nng lng ca phtn : = hf = h
l
c
.
- Phng trnh Anh-xtanh : =
2
2
max
0
mv
A
+
.
- Hiu in th hm :
2
max
0
2
1
mv
eU
U
e
h
AK
=
=
.
V d 1: Khi chiu mt chm sng vo mt kim loi th c hin tng quang in xy ra. Nu dng hiu in th hm bng 3 (V) th cc lectron quang in b gi li khng bay sang anot c. Cho bit gii hn quang in ca kim loi l : 0 = 0,5 (m) ; h = 6,625.10-34 (J.s) ; c = 3.108 (m/s) ; -e = -1,6.10-19 (C). Tnh tn s ca chm nh sng ti kim loi.
V d 2: Chiu bc x c bc sng 0,35 (m) vo mt kim loi, cc lectron kim quang in bn ra u b gi li bi mt hiu in th hm. Khi thay chm bc x c bc sng gim 0,05 (m) th hiu in th hm tng 0,59 (V). Tnh in tch ca lectron quang in. Cho bit : h = 6,625.10-34 (J.s) ; c = 3.108 (m/s).
V d 3: Ln lt chiu hai bc x c bc sng 1 = 0,405 (m), 2 = 0,436 (m) vo b mt ca mt kim loi v o hiu in th hm tng ng Uh1 = 1,15 (V); Uh2 = 0,93 (V). Cho bit: h = 6,625.10-34 (J.s) ; c = 3.108 (m/s) ; e = 1,6.10-19 (C). Tnh cng thot ca kim loi ..
V d 4: Kim loi lm catot ca t bo quang in c gii hn quang in 0,32 (m). Chiu nh sng c bc sng 0,25 (m) vo catot ca t bo quang in trn.
Cho bit : h = 6,625.10-34 (J.s) ; c = 3.108 (m/s) ; me = 9,1.10-31 (kg) ; -e = -1,6.10-19 (C).
a) Tnh vn tc ban u cc i ca electron quang in.
b) Bit rng cc electron thot ra u b ht v anot, cng dng quang in bo ho bng 0,7 mA. Tnh s electron thot ra khi catot trong mi giy.
V d 5: Chiu bc x c bc sng
l
vo catot ca t bo quang in.dng quang in b trit tiu khi UAk
- 4,1V. khi UAK =5V th vn tc cc i ca electron khi p vo anot l:
A. 1,789.106m/s B. 1,789.105m/s C. 1,789.105 km/s B. 1,789.104 km/s
Dng 10: Chiu nh sng kch thch c bc sng thch hp vo b mt tm KL (hay qu cu) c c lp v in. Tnh hiu in th cc i m tm KL(hay qu cu) t c.
PPG: Khi chiu nh sng kch thch vo b mt KL th e quang in b bt ra, tm KL mt in t (-) nn tch in (+) v c in th l V. in trng do in th V gy ra sinh ra 1 cng cn AC = e.V ngn cn s bt ra ca cc e tip theo. Nhng ban u AC < Wdmax , nn e quang in vn b bt ra. in tch (+) ca tm KL tng dn, in th V tng dn. Khi V =Vmax th cng lc cn c ln ng bng Wdmax ca e quang in nn e khng cn bt ra.
Ta c:
2
ax0max
1
2
Me
eVmv
=
=>
ax
0
M
hchc
eVA
e
ll
=-=-
Vy
ax
0
11
()
M
hc
V
e
ll
=-
V d 1: Mt qu cu bng ng (Cu) c lp v in c chiu bi 1 bc x in t c = 0,14 (m), . Cho gii hn quang in ca Cu l 1 = 0,3 (m). Tnh in th cc i ca qu cu.
HD Gii:
348
ax
1966
0
116,625.10.3.1011
()()4,73
1,6.100,14.100,3.10
M
hc
VV
e
ll
-
---
=-=-=
V d 2: Cng thot electron khi ng l 4,57 eV. Chiu bc x c bc sng ( = 0,14 (m vo mt qu cu bng ng t xa cc vt khc. Tnh gii hn quang in ca ng v in th cc i m qu cu ng tch c.
HD Gii: (0 =
19
8
34
10
.
6
,
1
.
57
,
4
10
.
3
.
10
.
625
,
6
-
-
=
A
hc
= 0,27.10-6 m; Wd0 =
l
hc
- A = 6,88.10-19 J; Vmax =
e
W
d
0
= 4,3 V.
V d 3: Cng thot electron khi km l 4,25 eV. Chiu vo mt tm km t c lp v in mt chm bc x in t n sc th thy tm km tch c in tch cc i l 3 V. Tnh bc sng v tn s ca chm bc x.
HD Gii : Wd0max = eVmax = 3 eV; ( =
d0ax
W
m
hc
A
+
= 0,274.10- 6 m; f =
c
l
= 1,1.1014 Hz.
hc
l
V d 4: Hiu in th hm ca mt t bo quang in l 1,5 V. t vo hai u anot (A) v catot (K) ca t bo quang in trn mt in p xoay chiu: uAK = 3 cos (
3
100
p
p
+
t
) (V). Khong thi gian dng in chy trong t bo ny trong 2 pht u tin l:
A. 60s. B. 70s. C 80s. D 90s
Gii: Dng in chy qua t bo khi uAK
-1,5 V. Cn c vng trn lng gic
suy ra trong mi chu k T = 0,02 s thi gian chy qua t bo l
3
2
T
= 0,04/3 (s).
Trong 2 pht, (s chu k 120:0,02 = 6000) thi gian chy qua l: t = 2.120/3 = 80 s.
Chn C
V d 5: Chiu ln lt 3 bc x n sc c bc sng theo t l
5
,
1
:
2
:
1
:
:
3
2
1
=
l
l
l
vo catt ca mt t bao quang in th nhn c cc electron quang in c vn tc ban u cc i tng ng v c t l
k
v
v
v
:
1
:
2
:
:
3
2
1
=
, vi
k
bng:
A.
3
B.
3
/
1
C.
2
D.
2
/
1
(
)
2
2
2
2
2
2
2
2
4.(1)
2
(1)(2)3
3
22
:(2)32
221
(3)(2)1
62
(3)
1,5.2
hcmv
A
hcmv
hcmv
HDAk
k
hcmv
k
hcmv
Ak
l
l
l
l
l
=+
-=
=+==
-
-=-
=+
V d 6: Mt ngun sng c cng sut P=2W, pht ra nh sng c bc sng =0,597m ta ra u theo mi hng. Nu coi ng knh con ngi ca mt l 4mm v mt cn c th cm nhn c nh sng khi ti thiu c 80 phtn lt vo mt trong 1s. B qua s hp th phtn ca mi trng. Khong cch xa ngun sng nht m mt cn trng thy ngun l A. 27 km B. 470 km C. 6 km D. 274 km
Gii:Cng sng I ti im cch ngun R c tnh theo cng thc: I =
2
4
R
P
p
.
Nng lng nh sng m mt c th nhn c:
W = IS = I
4
2
d
p
=
2
4
R
P
p
EMBED Equation.3
4
2
d
p
=
2
2
16
R
Pd
(d ng knh mt) m W = 80
l
hc
---->
80
l
hc
=
2
2
16
R
Pd
=> R =
hc
Pd
80
.
16
2
l
= 0,274.106 (m) = 274 (km). Chn D
4.Bi tp tng hp c hng dn:
Bi 1: Khi chiu bc x c bc sng 0,4 (m vo catt ca mt t bo quang in, mun trit tiu dng quang in th hiu in th gia A v K bng -1,25V.
a. Tm vn tc ban u cc i ca cc e quang in.
b. Tm cng thot ca cc e ca kim loi lm catt (tnh ra eV).
HD Gii :a.
31
19
0
2
max
0
10
.
1
,
9
25
,
1
.
10
.
6
,
1
.
2
2
|
|
2
-
-
=
=
=
m
eU
v
eU
mv
h
h
= 0,663.106 m/s.
b. Cng thot:
(
)
348
2
2316
0max
6
16,625.10.3.101
.9,1.10.0,663.10
20,4.102
hc
Amv
l
-
-
-
=-=-
EMBED Equation.3
eV
J
855
,
1
10
.
97
,
2
19
=
=
-
.
Bi 2: Cng thot ca vnfram l 4,5 eV
a. Tnh gii hn quang in ca vnfram.
b. Chiu vo vnfram bc x c bc sng ( th ng nng ban u cc i ca e quang in l 3,6.10-19J. Tnh (.
c. Chiu vo tm vnfram mt bc x c bc sng (. Mun trit tiu dng quang in th phi cn mt hiu in th hm 1,5V. Tnh (?
HD Gii :
a.
276
,
0
10
.
6
,
1
.
5
,
4
10
.
3
.
10
.
625
,
6
A
hc
19
8
34
0
=
=
=
l
-
-
(m.
b.
348
1919
6,625.10.3.10
0,184
4,5.1,6.103,6.10
hchc
AW
AW
l
l
-
--
=+===
++
(m.
c.
(
)
(
)
348
1919
6,625.10.3.10
'0,207
'
4,5.1,6.101,5.1,6.10
h
h
hchc
AeU
AeU
l
l
-
--
=+===
+
+--
(m.
Bi 3: Cng ti thiu bc mt lectron ra khi b mt mt tm kim loi ca mt t bo quang in l 1,88eV. Khi chiu mt bc x c bc sng 0,489 (m th dng quang in bo ha o c l 0,26mA.
a. Tnh s lectron tch ra khi catt trong 1 pht.
b. Tnh hiu in th hm trit tiu hon ton dng quang in.
HD Gii :
a. Ibh = n
e
= 26.10-5A. (n l s lectron tch ra khi catt trong 1s). n =
14
19
5
10
.
25
,
16
10
.
6
,
1
10
.
26
=
-
-
;
S lectron tch ra khi K trong 1 pht: N=60n = 975.1014.
b.
eV
eV
A
hc
mv
eU
h
66
,
0
88
,
1
54
,
2
88
,
1
10
.
6
,
1
.
10
.
489
,
0
10
.
3
.
10
.
625
,
6
2
19
6
8
34
2
0
=
-
=
-
=
-
=
=
-
-
-
l
.Hiu in th hm Uh = 0,66V.
Bi 4: Catt ca t bo quang in bng xdi (Cs) c gii hn quang in (0=0,66(m. Chiu vo catt bc x t ngoi c bc sng ( =0,33 (m. Hiu in th hm UAK cn t gia ant v catt trit tiu dng quang in l bao nhiu?
HD Gii :
- trit tiu dng quang in, cng ca lc in trng phi trit tiu c ng nng ban u cc i ca quang lectron (khng c mt lectron no c th n c ant)
(
)
(
)
2
348
0max
619
000
6,625.10.3.10
1,88
2
0,66.10.1,6.10
AKAK
mv
hchchchc
eUUV
e
llll
-
--
==-===-=-
-
-Nh vy trit tiu hon ton dng quang in th: UAK ( 1,88V.
Bi 5: Khi chiu ln lt hai bc x c bc sng 0,25 (m v 0,3 (m vo mt tm kim loi th vn tc ban u cc i ca cc lectron quang in ln lt l 7,31.105 m/s v 4,93.105 m/s.
a. Tnh khi lng ca cc lectron.
b. Tnh gii hn quang in ca tm kim loi.
HD Gii :a.
2
mv
A
hc
2
max
01
1
+
=
l
;
2
mv
A
hc
2
max
02
2
+
=
l
EMBED Equation.3
)
2
v
2
v
(
m
1
1
hc
2
max
02
2
max
01
2
1
-
=
l
-
l
-
-
=
-
-
=
-
-
-
6
6
10
10
8
34
2
1
2
max
02
2
max
01
10
.
3
,
0
1
10
.
25
,
0
1
10
.
3049
,
24
10
.
4361
,
53
10
.
3
.
10
.
625
,
6
.
2
1
1
2
l
l
v
v
hc
m
m= 1,3645.10-36.0,667.106= 9,1.10-31 kg.
b. Gii hn quang in:
(
)
J
mv
hc
A
mv
A
hc
19
2
5
31
6
8
34
2
max
01
1
2
max
01
1
10
.
52
,
5
2
10
.
31
,
7
.
10
.
1
,
9
10
.
25
,
0
10
.
3
.
10
.
625
,
6
2
2
-
-
-
-
=
-
=
-
=
+
=
l
l
m
m
A
hc
m
l
36
,
0
10
.
6
,
3
10
.
52
,
5
10
.
3
.
10
.
625
,
6
7
19
8
34
0
=
=
=
=
-
-
-
Bi 6: a. Khi mt cht b kch thch v pht ra nh sng n sc mu tm c bc sng 0,4 (m th nng lng ca mi phtn pht ra c gi tr l bao nhiu? Bit h =6,625.10-34Js; c =3.108 m/s.
b. i vi nguyn t hir, khi lectron chuyn t qu o M v qu o K th nguyn t pht ra phtn c bc sng 0,1026 m. Ly h = 6,625.10-34J.s, e = 1,6.10-19 C v c = 3.108m/s. Nng lng ca phtn ny bng bao nhiu? Nu photon ny truyn vo nc c chit sut
3
4
=
n
th nng lng ca n thay i th no?
HD Gii :
a. Nng lng ca photon tng ng:
19
6
8
34
min
10
.
97
,
4
10
.
4
,
0
10
.
3
.
10
.
625
,
6
hc
-
-
-
=
=
l
=
e
J.
b. Nng lng ca photon tng ng:
348
19619
6,625.10.3.10
12,1
.1,6.100,1026.10.1,6.10
hc
e
l
-
---
===
eV
Tn s ca nh sng s khng thay i khi truyn qua cc mi trng khc nhau nn nng lng ca n cng khng thay i khi truyn t khng kh vo nc.
Bi 7: Cng thot lectron ca mt kim loi l 7,64.10-19J. Chiu ln lt vo b mt tm kim loi ny cc bc x c bc sng l (1 = 0,18 m, (2 = 0,21 m v (3 = 0,35 m . Ly h = 6,625.10-34J.s, c = 3.108 m/s.
a. Bc x no gy c hin tng quang in i vi kim loi ?
b. Tnh ng nng ban u cc i ca cc electron quang in.
c. Tnh ln ca in p trit tiu dng quang in trn.
HD Gii :
a. Gii hn quang in:
348
0
19
6,625.10.3.10
0,26
7,64.10
hc
m
A
lm
-
-
===
Ta c : (1, (2 < (0; vy c hai bc x u gy ra hin tng quang in cho kim loi .
b. (1, (2 gy ra hin tng quang in, chng ta hy tnh ton cho bc x c nng lng ca photon ln hn (bc x
1
l
)
Theo cng thc Einstein:
max
0
1
W
A
hc
+
=
l
EMBED Equation.3
EMBED Equation.3
J
A
hc
W
19
19
6
8
34
1
max
0
10
.
4
,
3
10
.
64
,
7
10
.
18
,
0
10
.
3
.
10
.
625
,
6
-
-
-
-
=
-
=
-
=
l
Mt khc:
s
m
s
m
m
W
v
mv
W
/
10
.
65
,
8
/
864650
10
.
1
,
9
10
.
4
,
3
.
2
.
2
2
1
5
31
19
max
0
max
0
2
max
0
max
0
=
=
=
=
-
-
c. ln in p trit tiu dng quang in:
V
e
W
U
U
e
W
h
h
125
,
2
10
.
6
,
1
10
.
4
,
3
19
19
max
0
max
0
=
=
=
=
-
-
Bi 8: Thc hin tnh ton tr li cc cu hi sau:
a. Electron phi c vn tc bng bao nhiu ng nng ca n bng nng lng ca mt photon nh sng c bc sng
0
5200
A
=
l
?
b. Nng lng ca photon phi bng bao nhiu khi lng ca n bng khi lng ngh ca electron? Cho khi lng ngh ca electron l
kg
m
e
31
10
.
1
,
9
-
=
.
HD Gii :
a. Theo bi ra:
l
hc
W
e
=
EMBED Equation.3
l
hc
v
m
e
=
2
2
1
EMBED Equation.3
s
m
m
hc
v
e
/
10
.
17
,
9
10
.
5200
.
10
.
1
,
9
10
.
3
.
10
.
625
,
6
.
2
2
5
10
31
8
34
=
=
=
-
-
-
l
b. Nng lng ca photon:
2
c
m
E
ph
=
Khi lng ca electron bng khi lng ngh ca electron
(
)
e
ph
m
m
=
nn:
(
)
MeV
J
c
m
E
e
51
,
0
10
.
19
,
8
10
.
3
.
10
.
1
,
9
14
2
8
31
2
=
=
=
=
-
-
Bi 9: Cng thot ca lectron i vi ng l 4,47 eV.
a.Tnh gii hn quang in ca ng?
b. Khi chiu bc x c bc sng = 0,14 (m) vo mt qu cu bng ng cch li vi vt khc th tch in n hiu in th cc i l bao nhiu ?
c. Khi chiu bc x c bc sng ' vo qu cu bng ng cch ly ci cc vt khc th qu cu t hiu in th cc i 3 (V). Tnh ' v vn tc ban u ca cc lectron quang in.
Cho bit : h = 6,626.10-34 (J.s) ; c = 3.108 (m/s) ; me = 9,1.19-31 (kg).
2
hc
l
HD Gii :
a.
nm
m
A
hc
278
10
.
278
9
0
=
=
=
-
l
b. Gi in th cc i ca qu cu bng ng l :Vmax .
Khi chiu bc x c bc sng n qu cu bng ng cch ly vi cc vt khc,
cc lectron quang c bt ra khi qu cu, in tch dng ca qu cu tngdn
nn in th V ca qu cu tng dn in th V ( Vmax .
khi cc lectron quang bt ra khi qu cu u b in trng ko tr li. ( Hnh 9).
Theo cng thc Einstein:
2
max
0
2
1
mv
A
hc
+
=
l
M in th cc i ca vt tnh theo cng thc:
max
2
max
0
2
1
V
e
mv
=
EMBED Equation.3
max
hc
AeV
l
=+
EMBED Equation.3
EMBED Equation.3
348
19
6
max
19
6,625.10.3.10
4,47.1,6.10
0,14.10
4,402
1,6.10
hc
A
VV
e
l
-
-
-
-
-
-
===
Li c:
max
2
max
0
2
1
V
e
mv
=
EMBED Equation.3
s
m
m
V
e
v
/
10
.
244
,
1
10
.
1
,
9
4
,
4
.
10
.
6
,
1
.
2
.
2
6
31
19
max
max
0
=
=
=
-
-
c. Tnh ' v v'0. Tng t:
'2
max0
1
'
'2
hc
AeVmv
l
-==
Suy ra:
)
(
166
,
0
'
'
max
m
eV
A
hc
m
l
=
+
=
. V: v'0 =
)
/
(
10
.
027
,
1
'
2
6
max
s
m
m
eV
e
=
.
Bi 10: Chiu bc x c bc sng ( = 0.6(m vo catot ca 1 t bo quang in c cng thot A= 1.8eV. Dng mn chn tch ra mt chm hp cc electron quang in v cho chng bay vo mt in trng t A n B sao cho UAB = -10V. Vn tc nh nht v ln nht ca electron khi ti B ln lt l:
A.18,75.105 m/s v 18,87.105 m/sB.18,87.105m/s v 18,75.105m/s
C.16,75.105m/s v 18.87.105m/sD.18,75.105m/s v 19,00.105m/s
Gii: (0 =
A
hc
=
348
6
19
6.625.10.3.10
0,69.100,69
1,8.1,6.10
mm
m
-
-
-
==
;
-Khi Vn tc ban u cc i ca e theo chiu tng tc vi UAB th ta c vn tc ln nht ca electron khi ti B l v: Gi v ( Hay vmax ) l vn tc cc i ca e khi n B. p dng nh l ng nng:
22
0
11
//
22
AB
mvmveU
-=
=>
22
0
11
//
22
AB
mvmveU
=+
=>
2
1
//
2
AB
mvAeU
e
=+-+
2
0
111
()//
2
AB
mvhceU
ll
=-+
=>
max
0
2//
211
()
AB
eU
hc
v
mm
ll
=-+
Th s :
34819
5
max
31631
2.6.625.10.3.10112.1,6.10
().1019,00.10/
9.1.10.100,60,699.1.10
vms
--
---
=-+=
-Khi vn tc ban u ca e bng 0 th ta c vn tc nh nht ca electron khi ti B l vmin :
2
min
1
2
AB
mveU
=
=>
min
2
AB
veU
m
=
Th s :
19
5
min
31
2.1,6.10
.1018,75228.10/
9.1.10
vms
-
-
==
p n D
Bi 11: Chiu bc x c tn s f1 vo qu cu kim loi t c lp th xy ra hin tng quang in vi in th cc i ca qu cu l V1 v ng nng ban u cc i ca e quang in ng bng mt na cng thot ca kim loi. Chiu tip bc x c tn s f2 = f1 + f vo qu cu th in th cc i ca qu cu l 5V1. Hi chiu ring bc x c tn s f vo qu cu trn (ang trung ha v in) th in th cc i ca qu cu l:
A. 2 V1 B. 2,5V1 C. 4V1. D. 3V1..
* Chiu f1 th:
A
A
A
mv
A
hf
5
,
1
2
1
2
1
2
max
0
1
=
+
=
+
=
in th cc i:
1
1
V
e
A
hf
+
=
hay
A
eV
2
1
1
=
* Chiu f2=f1+f th:
A
A
A
V
e
A
V
e
A
hf
hf
hf
5
,
3
5
,
0
.
5
5
1
2
1
2
=
+
=
+
=
+
=
+
=
* Chiu f th:
max
V
e
A
hf
+
=
Vy:
1
1
max
max
max
1
max
2
2
5
,
1
5
,
3
5
,
3
V
V
e
A
V
e
V
e
A
A
A
V
e
A
hf
A
V
e
A
hf
=
=
=
+
=
-
+
=
-
+
=
p n A
Bi 12: Chiu bc x c tn s f1 vo qu cu kim laoij t c lp th xy ra hin tng quang in vi in th cc i ca qu cu l V1 v ng nng ban u cc i ca electron quang in ng bng mt phn ba cng thot ca kim loi. chiu tip bc x c tn s f2=f1+f vo qu cu kim loi th in th cc i ca qu l 7V1. hi chiu ring bc x c tn s f vo qu cu kim loi trn (ang trung ha in) th in th cc i ca qu cu l: p s: 3V1
Gii: in th ca qu cu t c khi e(Vmax 0) =
h
eU
mv
=
2
2
max
0
ta c hf1 = A +
2
2
1
mv
= A + eV1 (1) Vi A =
1
2
1
3
2
3
eV
mv
=
(2)
h(f1+ f) = A +
2
2
21
mv
= A + eV2 = A + 7eV1 (3) hf = A +
2
2
mv
= A + eV (4)
Ly (3) (1) : hf = 6eV1 => 6eV1 = A + eV=> eV = 6eV1 A = 3eV1 . Do V = 3V1
Bi 13: Mt b pin quang in gm nhiu pin mc ni tip. Din tch tng cng ca cc pin l 0,4 m2. Dng nh sng chiu vo b pin c cng 1000 W/m2. Khi cng dng in m b pin cung cp cho mch ngoi l 2,85A th in p o c hai cc ca b pin l 20 V. Hiu sut ca b pin l A. 43,6% B. 14,25% C. 12,5% D. 28,5%
Gii: Cng sut nh sng chiu vo din tch b mt b pin: P = 1000. 0,4 = 400 W.
Cng sut tiu th mch ngoi: P = UI = 57 W
Hiu sut ca b pin H =
P
P
'
=
400
57
= 0,1425 = 14,25% Chn p n B
Bi 14: Chiu ln b mt mt tm kim loi c cng thot electrn l A = 2,1 eV chm nh sng n sc c bc sng =0,485m . Ngi ta tch ra mt chm hp cc electrn quang in c vn tc ban u cc i hng vo mt khng gian c c in trng u E v t trng u B . Ba vc t v , E , B vung gc vi nhau tng i mt. Cho B = 5.10-4 T . cc electrn vn tip tc chuyn ng thng v u th cng in trng E c gi tr no sau y ?A. 201,4 V/m. B. 80544,2 V/m. C. 40.28 V/m. D. 402,8 V/m.
Gii:
Vn tc ban u cc i ca electron;
v =
)
(
2
A
hc
m
-
l
=
)
10
.
6
,
1
.
1
,
2
10
.
485
,
0
10
.
3
.
10
.
625
,
6
(
10
.
1
,
9
2
19
6
8
34
31
-
-
-
-
-
= 0,403.106 m/s
electron vn tip tc chuyn ng thng u th lc Lorenxo cn bng vi lc in tc dng ln electron: Bve = eE =-> E = Bv = 5.10-4. 0,403.106 = 201,4 V/m. Chn A
5.Trc nghim:
Cu 1. nh sng v nh sng vng c bc sng ln lt l
D
l
=0,768
m
m
v
l
=0,589
m
m
.Nng lng photon tng ng ca hai nh sng trn l
A.
D
e
=2,588.10-19j
V
e
=3,374.10-19 j * B.
D
e
=1,986.10-19 j
V
e
=2,318.10-19j
C.
D
e
=2,001`.10-19j
V
e
=2,918.10-19 j D. mt p s khc
Cu 2 : Cho h=6,625.10-34Js, c=3.108m/s. Tnh nng lng ca phtn c bc sng 500nm?
A. 4.10-16J B. 3,9.10-17J C. 2,5eV* D. 24,8eV
Cu 3: Mt ngn n pht ra nh sng n sc c bc sng 0,3975
m
m
vi cng sut pht x l 10 w. S phooton ngn n pht ra trong mt giy l
A. 3.1019 ht B. 2.1019 ht* C. 5. 1019 ht D. 4.1019 ht
Cu 4: Mt kim loi c gii hn quang in l 0,3(m .Bit h = 6,625.10-34Js ; c = 3.108m/s .Cng thot ca lectron ra khi kim loi l .
A. 6,625.10-19J * B. 6,625.10-25J C. 6,625.10-49J D. 5,9625.10-32J
Cu 5 : Gii hn quang in ca Cs l 6600A0. Cho hng s Planck h = 6,625.10-34Js , vn tc ca nh sng trong chn khng c = 3.108 m/s. Cng thot ca Cs l bao nhiu ?
A. 1,88 eV *B. 1,52 eVC. 2,14 eVD. 3,74 eV
Cu 6 : Cng thot electrn ra khi mt kim loi l A = 1,88 eV. Gii hn quang in ca kim loi l :
A. 0,66.10-19
m
m B. 0,33
m
m C. 0,22
m
m D. 0,66
m
m *
Cu 7 : Bit cng cn thit bt electrn ra khi t bo quang in l A = 4,14eV. Gii hn quang in ca t bo l:
A. (0 = 0,3(m * B. (0 = 0,4(m C. (0 = 0,5(m D. (0 = 0,6(m
Cu 8 : Cng thoat electrn cua mt kim loai la 2,36eV. Cho h = 6,625.10 -34Js ; c = 3.108m/s ;1eV = 1,6.10 -19J . Gii hn quang in ca kim loi trn l :
A. 0,53 (m*B. 8,42 .10 26m C. 2,93 (mD. 1,24 (m
Cu 9 : Trong hin tng quang in, bit cng thot ca cc electrn quang in ca kim loi l A = 2eV. Cho h = 6,625.10-34Js , c = 3.108m/s. Bc sng gii hn ca kim loi c gi tr no sau y ?
A. 0,621(m *B. 0,525(mC. 0,675(mD. 0,585(m
Cu 10: Gii hn quang in ca natri l 0,5
m
m
. Cng thot ca km ln hn ca natri 1,4 ln. Gii hn quang in ca km :
A. 0,7
m
m
B. 0,36
m
m
* C. 0,9
m
m
D. 0,36 .10 -6
m
m
Cu 11 : Catod ca mt t bo quang in c cng thot A = 3,5eV. Cho h =
34
6,625.10
-
Js ; m =
31
9,1.10
-
kg ; e =
19
1,6.10
-
C .Tnh gii hn quang in ca kim loi dng lm catod .
A.
355
m
m
B.
35,5
m
m
C.
3,55
m
m
D.
0,355
m
m
*
Cu 12 : Mt bc x in t c bc sng ( = 0,2.10-6m. Tnh lng t (nng lng phtn) ca bc x .
A. ( = 99,375.10-20J * B. ( = 99,375.10-19J C. ( = 9,9375.10-20J D. ( = 9,9375.10-19J
Cu 13 : Nng lng ca phtn l 2,8.10-19J. Cho hng s Planck h = 6,625.10-34J.s ; vn tc ca nh sng trong chn khng l c = 3.108m/s. Bc sng ca nh sng ny l :
A. 0,45
m
mB. 0,58
m
mC. 0,66
m
mD. 0,71
m
m *
Cu 14 : Mt kim loi lm catt ca t bo quang in c cng thot l A = 3,5eV. Chiu vo catt bc x c bc sng no sau y th gy ra hin tng quang in. Cho h = 6,625.10-34Js ; c = 3.108m/s
A.
l
= 3,35
m
m
B.
l
= 0,355.10- 7m * C.
l
= 35,5
m
m
D.
l
= 0,355
m
m
Cu 15 : Kim loi lm catt ca t bo quang in c cng thot A= 3,45eV. Khi chiu vo 4 bc x in t c (1= 0,25 m, (2= 0,4 m, (3= 0,56 m, (4= 0,2 m th bc x no xy ra hin tng quang in
A. (3, (2B. (1, (4 *C. (1, (2, (4D. c 4 bc x trn
Cu 16 : Bc sng di nht bt c electrn ra khi 2 kim loi a v b ln lt l 3nm v 4,5nm. Cng thot tng ng l A1 v A2 s l :
A. A2 = 2 A1.B. A1 = 1,5 A2 *C. A2 = 1,5 A1.D. A1 = 2A2
Cu 17. Gii hn quang in ca kim loi l 0. Chiu vo catt ca t bo quang in ln lt hai bc x c bc sng 1=
2
0
l
v 2=
3
0
l
. Gi U1 v U2 l in p hm tng ng trit tiu dng quang in th
A. U1 = 1,5U2. B. U2 = 1,5U1. C. U1 = 0,5U2 .* D. U1 = 2U2.
Cu 18. Cng thot electron ca mt kim loi l A0, gii hn quang in l (0. Khi chiu vo b mt kim loi chm bc x c bc sng
l
=
0
3
l
th ng nng ban u cc i ca electron quang in bng:
A. 2A
0
.* B. A
0
.C. 3A
0
.D. A
0
/3
Cu 19. Bit bc sng ca nh sng kch thch bng mt na gii hn quang in
2
0
l
l
=
v cng thot in t khi catt l
0
A
th ng nng ban u cc i ca quang in t phi bng :
A.
0
A
* B.
0
2
1
A
C.
0
4
1
A
D.
0
3
1
A
Cu 20. Chiu ln lt 2 bc x c bc sng
m
m
m
l
m
l
5
,
0
;
25
,
0
2
1
=
=
vo catt ca mt t bo quang in th vn tc ban u cc i ca electron quang in l
1
v
v
1
2
2
1
v
v
=
. Bc sng gii hn quang in l:
A.
m
m
75
,
0
* B.
m
m
6
,
0
C.
m
m
375
,
0
D.
m
m
72
,
0
Cu 21: nh sng c tn s f1 chiu ti t bo quang in th hiu in th hm c ln l U1. Nu chiu ti t bo quang in nh sng c tn s f2 th hiu din th hm c ln l
A.
(
)
21
1
hf-f
U-
e
. B.
(
)
12
1
+
hff
U
e
+
. C.
(
)
12
1
+
hff
U-
e
. D.
(
)
21
1
hf-f
U
e
+
.*
Cu 22: Cng thc no sau khng dng tnh gii hn quang in (0 ca kim loi dng lm catt t bo quang in? ( Uh l ln hiu in th hm, f v ( l tn s v bc sng nh sng kch thch)
A. (0 =
hc
A
. B. (0 =
2
0max
1
mv
1
-
2hc
C. (0 =
h
1
eU
-
hc
f
c
D. (0 =
h
1
eU
1
-
f2hc
Cu 23: Khi chiu mt bc x in t
0,546
m
lm
=
ln b mt mt kim loi dng lm catot ca mt t bo quang in, thu c dng bo ha c cng I = 2.10-3A. Cng sut bc x in t l 1,515W. Hiu sut lng t bng:
A.
2
0,5.10
-
B.
2
0,3.10
-
C.
3
0,3.10
-
D.
3
0,5.10
-
Cu 24: Chiu lin tc mt chm tia t ngoi c bc sng
l
= 147nm vo mt qu cu bng ng c lp v in. Sau mt thi gian nht nh in th cc i ca qu cu bng 4V. Gii hn quang in ca ng nhn gi tr no? (h= 6,6.10-34J.s ; c=3.108m/s;)
A. 310nmB. 350nmC. 240nmD. 280nm
Cu 25: Chiu bc x c bc sng =0,533m ln tm kim loi c cng thot A=3.10-19J. lectron quang in bc ra cho bay vo t trng u theo hng vung gc vi cc ng cm ng t B ca t trng. Bit c electron chuyn ng theo qu o trn bn knh ln nht R=22,75mm. ln cm ng t B ca t trng l
A. 10-4 T. B. 4.10-5 T. C. 10-5 T. D. 2.10-4 T.
Cu 26: Khi chiu mt bc x in t
0,546
m
lm
=
ln b mt mt kim loi dng lm catot ca mt t bo quang in, thu c dng bo ha c cng I = 2.10-3A. Cng sut bc x in t l 1,515W. Hiu sut lng t bng:
A.
2
0,5.10
-
B.
2
0,3.10
-
C.
3
0,3.10
-
D.
3
0,5.10
-
Cu 27: o khong cch t Tri t ln Mt Trng ngi ta dng mt tia laze pht ra nhng xung nh sng c bc sng 0,52
m
m
, chiu v pha Mt Trng.Thi gian ko di mi xung l 10-7 (s) v cng sut ca chm laze l 100000 MW. S phtn cha trong mi xung l
A. 2,62.1022 ht . B. 2,62.1015 ht . C. 2,62.1029 ht . D. 5,2.1020 ht .
6.Bi tp trc nghim rn luyn
Bi 1: Chiu bc x c bc sng
l
=0,18
m
m vo ca tt ca mt t bo quang in.KL dng lm ca tt c gii hn quang in l
0
l
=0,3
m
m.Tr li cc cu hi sau:
Cu 1:Cng thot ca e ra khi t bo quang in l bao nhiu?
A:4,14eV; B:66,25eV; C:6,625eV; D:41,4eV.
Cu 2:.Xc nh hiu in th Uh dng quang in trit tiu.
A:5,52V; B:6,15V; C:2,76V; D:2,25V.
Cu 3:ng nng ban u cc i ca e l bao nhiu?
A:25,5eV; B:2,76eV; C:2,25eV; D:4,5eV.
Bi 2:Kim loi dng lm ca tt ca mt t bo quang in c cng thot A=2,2eV.Chiu vo ca tt mt bc x in t c bc sng
l
.bit Uh=0,4V.Vn tc ban u cc i ca e l bao nhiu?
A:3,75.105m/s; B:3,5.105m/s; C:3,75.104m/s; D:3,5.104m/s.
Bi 3:Chiu bc x c bc sng
l
=0,552
m
m vo ca tt ca mt t bo quang in th dng quang in bo ha l Ibh=2mA, cng sut ngun sng chiu vo ca tt l p=1,2w.Tnh hiu sut lng t ca hin tng quang in.
A:0,650%; B:0,3750% ; C: 0,550%; D: 0,4250%.
Bi 4:Chiu bc x c bc sng
l
=0,4
m
m vo ca tt ca mt t bo quang in.Cng thot ca electron ca kim loi lm ca tt l A=2eV.Tr li cc cu hi sau:
Cu 1: trit tiu dng quang in phi t gia a nt v ca tt mt hiu in th UAK c gi tr no sau y.
A:UAK
-1,1V; B:UAK
1,1V ; C: UAK =-1,1V; D:UAK =1,1V.
Cu 2:t gia Ant v catt mt hiu in th UAK=5V.ng nng cc i ca quang e khi ti ant c gi tr no sau y:
A:8,1eV; B:6,1eV; C:4,1eV; D:6,6eV.
Bi 5: Mt n Na chiu sng c cng sut pht x p=100w.Bc sng ca nh sng do n pht ra l 0,589
m
ms ph tn do n ng pht ra trong 30 giy l bao nhiu?
A:9.1021; B:9.1018; C:12.1022; D:6.1024.
Bi 6:Cho
348
h6,625.10Js, c=3.10m/s
-
=
. ng lng ca phtn c tn s
14
v6.10Hz
=
l :
A:2,5.10-28 kg.m/s B:1,5.10-28 kg.m/s; C:13,25.10-28 kg.m/s; D: 0,25.10-28 kg.m/s
Bi 7: Khi t mt hiu in th ngc 0,8V ln hai cc ca t bo quang in th khng c mt electron no n c ant ca t bo quang in . Vn tc ban u cc i ca cc quang electron bn ra khi catt l :
A:5,3.106 m/s B:0,3.106 m/s; C:0,65.106 m/s; D:0,53.106 m/s
Bi 8: Khi chiu mt bc x in t n sc bc sng =0,41m vo catt ca mt t bo quang in th c hin tng quang in xy ra. trit tiu dng quang in ngi ta t mt hiu in th ngc l 0,76V. Cho
348-19
h6,625.10Js, c=3.10m/s, 1eV=1,6.10J
-
=
. Cng thot ca electron i vi kim loi dng lm catt s l :
A:36,32.10-20 J; B:3,3125.10-20J; C:0,3125.10-20J; D:33,25.10-20J;
Bi 9: Gii hn quang in ca kim loi dng lm catt ca t bo quang in l 0,5m. Cho
348-19
h6,625.10Js, c=3.10m/s, 1e=1,6.10C
-
=
. Khi chiu nh sng n sc bc sng =0,36m vo catt ca t bo quang in th hiu in th hm khng c mt electron no n c ant s l :
A :Uh= 9,7V; B: Uh= 0,97V ; C:Uh=1,97V; D:Uh=0,57V
Bi 10: Khi chiu mt chm sng n sc vo mt kim loi c hin tng quang in xy ra. Nu dng mt hiu in th hm bng 3,0 V th cc quang electron khng ti ant c. Cho bit tn s gii hn ca kim loi l
14-1-34-19
6.10 s, =6,625.10Js, e=1,6.10C
. Tn s ca chm nh sng ti s l :
A:1,5.1014 HZ; B:1,25.1014 HZ; C:13,25.1014 HZ; D:25.1014 HZ;
Bi 11. Chiu mt chm bc x c bc sng ( = 1800A0 vo mt tm kim loi. Cc electron bn ra c ng nng cc i bng 6eV. Cho bit h = 6,625.10-34J.s; c = 3.108m/s; e = 1,6.10-19C.Tr li cc cu hi sau:
Cu 1 :Tnh cng thot tng ng vi kim loi dng.
A. 24.10-20J. B. 20.10-20J. C. 18.10-20J. D. 14.10-20J.
Cu 2: Khi chiu vo tm kim loi bc x c bc sng ( = 5000A0 th c hin tng quang in xy ra khng? Nu c hy tnh ng nng cc i ca electron bn ra.
A. 25,6.10-20J. B. 51,2.10-20J. C. 76,8.10-20J. D. 85,6.10-20J
Bi 12: Catt ca mt t bo quang in c cng thot electron bng 4eV, ngi ta chiu n t bo quang in nh sng n sc c bc sng ( = 2600A0. Cho bit h = 6,625.10-34J.s; c = 3.108m/s; me = 9,1.10-31kg ; e = 1,6.10-19C.
Tr li cc cu hi sau:
Cu 1:Tm gii hn quang in ca kim loi dng l catt.
A. 3322A0.B. 4028A0. C. 4969A0. D. 5214A0. E. 6223A0.
Cu 2:Tm vn tc ban u cc i ca cc electron .
A. 6,62.105m/s. B. 5,23.105m/s. C. 4,32.105m/s. D. 4,05.105m/s.
Cu 3: Cho bit tt c cc electron thot ra u b ht v ant v cng dng quang in bo ho Ibh = 0,6mA, tnh s electron tch ra khi catt trong mi giy.
A. 3000.1012ht/s. B. 3112.1012ht/s.
C. 3206.1012ht/s. D. 3750.1012ht/s. E. 3804.1012ht/s.
Bi 13: Catt ca mt t bo quang in c gii hn quang in 6000A0. Chiu n t bo quang in mt nh sng n sc c ( = 4000A0 . Cho h = 6,625.10-34J.s; c = 3.108m/s; me = 9,1.10-31kg ; e = 1,6.10-19C. Tr li cc cu hi sau:
Cu 1:Tnh cng thot A ca cc electron .
A. 1,68eV. B. 1,78eV.C. 1,89eV. D. 2,07eV.
Cu 2 :Tm vn tc ban u cc i ca cc electron.
A. 5,6.105m/s. B. 6,03.105m/s. C. 6,54.105m/s. D. 6,85.105m/s.
Cu 3 :Tm hiu in th hm cc electron khng v n ant.
A. 0,912V. B. 0,981V. C. 1,025V. D. 1,035V.
Bi 14: Ln lt chiu 2 bc x c tn s f1 =0,75.1015Hz v f2 = 0,5.1015 Hz vo b mt ca nti v o hiu in th hm tng ng U1 = 1,05V v U2 = 0,03V. Tnh cng thot ca na tri.Cho bit : h = 6,625.10-34J.s
Bi 15: Chiu chm bc x c bc sng = 0,2 (m) vo mt tm kim loi, cc lectron quang in bn ra c ng nng cc i bng 5(eV). Khi chiu vo tm kim loi 2 bc x c bc sng 1 = 1,6 (m) v 2 = 0,1 (m) th c hin tng quang in xy ra khng ? Nu c, hy tnh ng nng cc i ca cc lectron quang in bn ra. Cho h = 6,625.10-34 (J.s) ; c = 3.108 (m/s).
S 15: Hin tng quang in c bc sng 2 to ra. ng nng: W2 = 11,21 (eV).
Bi 16: Chiu mt chm sng c tn s f = 7.108 (Hz) ln lt vo hai bn kim loi nhm v kali. Gii hn quang in ca nhm l 01 = 0,36 (m), ca kali l 02 = 0,55 (m). Cho : h = 6,625.10-34 (J.s); c = 3.108 (m/s); me = 9,1.10-31 (kg).
a. Tnh bc sng ca chm nh sng .
b. Hin tng g s xy ra khi chiu chm nh sng vo bn nhm v bn kali. Tnh vn tc ban u cc i ca lectron quang in khi bt ra khi bn kim loi.
S 16: a. = 0,4286 m.
b. Nu > 01 : hin tng quang in khng xy ra vi bn nhm.
Nu < 02 : hin tng quang in xy ra vi bn kali. V02 = 4,741.105 (m/s) .
Bi 17: Ln lt chiu hai bc x c tn s f1 = 75.1013 (Hz) v f2 = 39.1013 (Hz) vo b mt mt tm kim loi v o hiu in th hm tng ng l U1 = 2 (V) v U2 = 0,5 (V). Tnh hng s P-lng.
Cho bit : c = 3.108 (m/s) ; e = 1,6.10-19 (C) S 17: h = 6,666.10-34 (J.s).
Bi 18: Ln lt chiu hai bc x c tn s f1 = 0,75.1015 (Hz) v f2 = 0,5.1015 (Hz) vo b mt ca Natri v o hiu in th hm tng ng U1 = 1,05 (V) v U2 = 0,03 (V). Tnh cng thot ra ca Natri.
Cho bit: h = 6,625.10-34 (J.s). S 18: A = 2,05 (eV).
Bi 19: Ln lt chiu hai bc x c tn s f1 = 9,375.1014 (Hz) v f2 = 5,769.1014 (Hz) vo mt tm kim loi lm catt ca t bo quang in, ngi ta o c t s cc vn tc ban u ca cc lectron quang in bng 2. Tnh cng thot ra ca kim loi . Cho bit: h = 6,625.10-34 (J.s). S 19: A = 3,03.10-19 (J).
Bi 20: Chiu ln lt hai bc x c bc sng
1
0,35
m
lm
=
v
2
0,54
m
lm
=
vo mt tm kim loi, ta thy t s vn tc ban u cc i bng 2. Cng thot ca electron ca kim loi l:
A.2,1eV. B.1,3eV. C.1,6eV. D.1,9eV.
Bi 21: .Ln lt chiu vo catt ca mt t bo quang in cc bc x in t gm bc x c bc sng 1 = 0,26 m v bc x c bc sng 2 = 1,21 th vn tc ban u cc i ca cc lectrn quang in bt ra t catt ln lt l v1 v v2 vi v2=
3
4
v1 . Gii hn quang in 0 ca kim loi lm catt ny l
A.0,42 m. B.0,45 m. C.1,00 m. D.0,90 m.
Bi 22: B mt c ch ca catt ca t bo quang in nhn c cng sut chiu sng ca nh sng c bc sng ( =0,40.10-6m l P = 3 mW. Cng dng in bo ho Ibh = 6,43.10-6 A. Xc nh hiu sut quang in.
A. .0,665% B. 66,5% C. 0,0665 % D. 6,65%
Bi 23: Catt ca t bo quang in c cng thot lectron l 3,5eV. Chiu vo catt chm nh sng c bc sng
l
th dng quang in trit tiu khi UAK
- 2,5V. Bc sng ca nh sng kch thch l:
A.
l
= 0,365
m
mB.
l
= 0,207
m
m C.
l
= 0,675
m
mD.
l
= 0,576
m
m
Bi 24: Mt n Lade c cng sut pht sng 1W pht nh sng n sc c bc sng 0,7(m. Cho h = 6,625.10-34 Js, c = 3.108m/s. S phtn ca n pht ra trong 1 giy l:
A. 3,52.1016.B. 3,52.1019 . C. 3,52.1018 .D. 3,52.1020 .
II. QUANG PH VCH CA NGUYN T HYR
1. Tm tt l thuyt v cng thc: Tin Bo :
nmnm
nm
hc
hfEE
e
l
===-
+ Bn knh qu o dng th n ca electron trong nguyn t hir: rn = n2r0
Vi r0 =5,3.10-11m l bn knh Bo ( qu o K)
+ Khi nguyn t ang mc nng lng cao chuyn xung mc nng lng thp th pht ra photon, ngc li chuyn t mc nng lng thp chuyn ln mc nng lng cao nguyn t s hp thu photon
hf
E
E
thp
cao
=
-
Lu : Bc sng di nht (NM khi e chuyn t N ( M.
Bc sng ngn nht ((M khi e chuyn t ( ( M.
+Bc sng pht ra khi nguyn t chuyn mc nng lng:
nm
EE
e
=-
nmnm
nm
hc
hfEE
l
==-
1
nm
nm
EE
hc
l
-
=
=>
0
22
11
()
nm
nm
hchc
EE
E
nm
l
==
-
-
+Tn s ca phtn bc x .
nm
nm
nm
EE
c
f
h
l
-
==
Vi En > Em.
+Mi lin h gia cc bc sng v tn s ca cc vch quang ph ca nguyn t hir:
21
32
31
1
1
1
l
l
l
+
=
v
21
32
31
f
f
f
+
=
(nh cng vct)
+Cng thc thc nghim:
22
111
H
R
mn
l
=-
+Hng s Rydberg:
77
0
13,6.
1,0969140.101,097.10
..
H
E
e
Rmm
hchc
====
( trong my tnh Fx th RH l R( )
( Cc dy Quang ph ca nguyn t hidr
- Dy Laiman: khi e ( n>1) v qu o K(m=1) th pht ra cc vch thuc dy Laiman: m = 1; n = 2,3,4
-
=
2
2
0
1
1
1
1
1
n
hc
E
n
l
vi
2
n
Cc vch thuc vng t ngoi
- Dy Banme: Khi e chuyn t qu o ngoi (n>2) v qu o L(m=2) th pht ra cc vch thuc dy Banme . m = 2; n = 3,4,5:
-
=
2
2
0
2
1
2
1
1
n
hc
E
n
l
vi
3
n
Gm 4 vch :
)
656
,
0
(
m
H
m
a
, lam
)
486
,
0
(
m
H
m
b
,
chm
)
434
,
0
(
m
H
m
g
, tm
)
410
,
0
(
m
H
m
d
v mt phn vng t ngoi
-Dy Pasen : khi cc e chuyn t qu o bn ngoi (n>3) v qu o M(m=3) : m = 3; n = 4,5,6:
-
=
2
2
0
3
1
3
1
1
n
hc
E
n
l
vi
4
n
Cc vch thuc vng hng ngoi
( Nng lng ca lectron trong nguyn t Hir c biu thc:
+Nng lng electron trong nguyn t hir:
0
22
13,6
()
n
E
EeV
nn
==-
Vi n ( N*: lng t s.
E0 = - 13,6eV: nng lng trng thi c bn ( Ch E0 < 0 )
2
hc
l
-n = 1 ng vi qu o K ( nng lng thp nht )
-n = 2 ng vi qu o L...
(
1;2,3,4,...
mn
==
dy Laiman (t ngoi);
(
2;3,4,5...
mn
==
dy Banme (mt phn nhn thy)
(
3;4,5,6,...
mn
==
dy Pasen (hng ngoi).
( Cc bc x ca dy Banmer( nhn thy):
+ Vch
H
a
:
32
ML
a
lll
==
:
32
32
hc
EE
l
=-
+ Vch lam
H
b
:
42
NL
b
lll
==
:
42
42
hc
EE
l
=-
+ Vch chm
H
g
:
52
OL
g
lll
==
:
52
52
hc
EE
l
=-
+ Vch tm
H
q
:
62
PL
q
lll
==
:
62
62
hc
EE
l
=-
( Cc vch c bc sng di nht ca cc dy:
+ Dy Laiman:
21
l
:
21
21
hc
EE
l
=-
;
+ Dy Banmer:
32
l
:
32
32
hc
EE
l
=-
;
+ Dy Paschen:
43
l
:
43
43
hc
EE
l
=-
( Ch : Khi nguyn t trng thi kch thch th n c th (kh d) pht ra s bc x in t cho bi:
(
)
!
2
!
2
!
2
-
=
=
n
n
C
N
n
; trong
2
n
C
l t hp chp 2 ca n.
2. Bi tp v cc dy quang ph hidr:
V d 1 v cc bc sng dy Lymain (t ngoi):
Khi electron trong nguyn t hiro mt trong cc mc nng lng cao L, M, N, O nhy v mc nng lng K , th nguyn t hiro pht ra vch bc x ca dy Lyman thuc vng t ngoi, c th nh sau:
+ Vch u tin c bc sng ln nht ng vi mc nng lng m =1 -> n= 2
21
21
.
hc
EE
l
=-
=
22
13,6()13,6()3.13,6
()()
214
eVeV
eV
---=
=>
21
..4
3.13,6.
hc
e
l
=
=1,215.10-7m = 0,1215(m
Hoc dng cng thc:
22
111
H
R
mn
l
=-
=> Th s
7
21
22
1
1,215.100,1215
11
()
12
H
mm
R
lm
-
===
-
+Vch th 2 ng mc nng lng m= 1-> n = 3,
7
31
22
1
1,025175.100,1025
11
()
13
H
mm
R
lm
-
===
-
+Vch th 3 ng mc nng lng m= 1--> n = 4,
8
41
22
1
9,72018.100,0972
11
()
14
H
mm
R
lm
-
===
-
+ Vch th 4 ng mc nng lng m= 1-> n = 5,
8
51
22
1
9,492365.100,0949
11
()
15
H
mm
R
lm
-
===
-
+ Vch th 5 ng mc nng lng m= 1-> n = 6,
8
61
22
1
9,37303.100,09373
11
()
16
H
mm
R
lm
-
===
-
- - - - - - - - - - - - - - - - - - -
+Vch cui cng c bc sng nh nht ng vi mc nng lng m =1-> n = (:
8
1
22
11
9,112670,0911
11
()
1
H
H
mm
R
R
lm
-
====
-
V d 2 v cc bc sng dy Banme ( c 4 vch nhn thy: , lam , chm , tm)
Khi electron trong nguyn t hiro mt trong cc mc nng lng cao M, N, O,P nhy v mc nng lng L ( ng vi trng hp nguyn t t mc cao hn tr v mc 2), th nguyn t hiro pht ra vch bc x thuc dy Balmer ,bn vch u vng nhn thy (, lam , chm , tm) v mt phn thuc vng t ngoi ca thang sng in t, c th nh sau:
a.Dng cng thc :
0
22
13,6
()
n
E
EeV
nn
==-
vi n = 2,3,4......
Cc bc x thuc dy banme ng vi trng hp nguyn t t mc cao hn tr v mc 2
+Vch th 1 c bc sng ln nht ( mu ) ng vi mc nng lng n =3 --> m = 2, theo Anh xtanh:
32
32
hc
EE
l
=-
=>
32
l
=
0,656
m
a
lm
=
( mu )
+Vch th 2 c mu lam ng mc nng lng n= 4 - > m = 2, c bc sng c xc nh:
42
42
hc
EE
l
=-
=>
42
l
=
0,486
m
b
lm
=
(mu lam )
+Vch th 3 c mu chm ng mc nng lng