Thiết kế bài giảng vật lí 12 nâng cao (tập 2) phần 2

CHL/ONG VH. Ll/pNG TLf ANH SANG
BAI43

HlfiN TI/CfNG QUANG D I £ N N G O A I
cAc DINH LUAT Q U A N G DifiN
I-MUCTl£u
1. Vi kie'n thflc
- Hieu va nhd dupe eac khai niem: hian tupng quang dipn, aiectron quang
dian, ddng quang didn, gidi ban quang dipn, ddng quang dian bao hoa, hiau
dian thd ham.
- Hidu dupe npi dung va nhan xet ka't qua thi nghiam khao sat dinh lupng
hian tupng quang dien.
- Hidu va phat tridn dupe edc dinh luat quang dian.
2, Vi ki nSng
- Ren luyan ki nang giai thieh cae hipn tupng vat li.
- Ren luyan ki nang phan tich ka't qua thi nghiem.

II - CHUXN BI
Gido vien
- Ve hinh 43.1,43.2,43.3 va 43.4 SGK tran gia'y khd AQ.
Hoc sinh
- 6n lai cac kidn thflc vd cdng eua lye dian trudng, dinh 11 dpng nang, khai niam
cudng dp ddng dien bao hoa.

130


m - THifiT K£

H O A T D 6 N G DAY

HOC

Hoat ddng cua hoc sinh

Trp giup cua giao vi§n

Hoat ddng 1
Kidm tra, chuan bj dieu kien
xua't phat. Dat van de
HS suy nghl ca nhan tim cau tra ldi

GV nau cau hdi kiem tra kidn thflc cu
- Lam thi nghiem vdi didt chan khong
theo so dd sau :

- Khi catdt bi ddt ndng, cae
electron ty do trong kim loai nhan
dupe nang lupng edn thiet dd bflt ra
khdi mat catdt. Do dd, trong dng
chan khdng cae electron ty do
chuydn dpng hdn loan. Khi khoa
K2 ddng, andt dupe ndi vdi cue
ducfng, catdt dupe ndi vdi eye am
cua ngudn dian thi eac electron se
chuyen dpng tfl catdt sang andt tao
ra ddng dipn. Khi do sd chi cua
miliampe ke khae khdng.
Ddt ndng catdt bang ngudn dian ^i, sau
dd md K], ddng K2 thi miliampe kd
chi the nao ? Tai sao ?

- Khao sat sy phu thupc cua cudng dp
ddng dian trong chan khdng vao hipu
dien the U dat gifla andt va catdt ngudi
ta thu dupe dudng dac tuydn vdn-ampe
I

O

u.

u
131


- Cudng dp ddng dian khi dd dat
gia tri bao hoa.

Nhan xet gi vd cudng dp ddng dian khi
TT
V, TT 9
V>U^'7

Hoat ddng 2
Tim hieu hien tupng quang dien
ngoai
HS chu y lang nghe va tra ldi eau
hdi cua GV

GV md ta thi nghiam phat hian hian
tupng quang dian do nha vat li ngudi

Dfle, Hee da lam, yau cdu HS ldng nghe
va tra ldi cac cau hdi dd tim hidu hian
tupng quang dien ngoai

t
- Do tia tfl ngoai chieu vao tdm
kem nan lam cho aiectron bi bat ra
khdi ta'm kem. Khi dung tam thuy
tinh khdng mau chan chum tia tfl
ngoai thi khdng hai la dien nghiem
khdng bj khep lai vi ta'm thuy tinh
da hdp thu hdu het eac tia tfl ngoai.

HS tiep thu, ghi nhd

- Chieu anh s ^ g uu qud7!| vao mpt tdm
kem P ban ddu tich dien am thi hai la
eua dian nghiem khep lai.
- Chdn chum tia hd quang bang tdm
thuy tinh khdng mau thi hai la eua dian
nghiem khdng bi khep lai.
Giai thich tai sao ?
GV thong bao
- Hian tupng anh sang lam bat eac
aiectron ra khdi bd mat kim loai gpi la
hian tupng quang dien ngoai, thudng gpi
tat la hien tupng quang dien.
- Cac eletron bj bat ra khdi bd mat kim
loai bj chieu sang gpi la quang aiectron,
hay cdn gpi la aiectron quang dien.

132


Hoat ddng 3
Tim hieu thi nghiam khao sat
dinh lupng hien tupng quang
dien
HS chu y ldng nghe va quan sat
hinh ve te bao quang dian tran gidy
khoAo.

GV gidi thiau te bao quang dien trong
thi nghiem khao sat djnh lupng
- Td bao quang dien la mpt binh bang
thach anh da hut hdt khdng khi, ban
trong cd hai dien eye: andt la mpt vdng
day kim loai; catdt cd dang mpt chdm
cdu bang kim loai ma ta edn khao sat.
GV md ta thi nghiam vdi td bao quang
dien, yau cdu HS tra ldi cac cau hdi dd
tim hieu thi nghiem khao sat dinh lupng
hian tupng quang dipn.
D

nF

^•0

O

1

B

P Ml

- Khi chidu chum sang cd budc
sdng ngdn vao catdt thi hien tupng
quang dien ngoai xay ra, trong td
bao quang dipn xudt hien cac
aiectron quang dian. Dudi tac dung
ciaa lye dian trudng, cae aiectron

Q

- Ddng khoa C va di chuyen con chay B
dd U^i^ >0. Chia'u chum sang cd budc
sdng ngan vao catdt thi hipn tupng gi
xay ra ? Nhan xet gi ve sd ehi cua dien
kdG?

133


quang dien chuyen dpng tfl catdt
sang andt tao thanh ddng dien chay
trong mach. Kim dien kd G Ipch
khdi vi tri 0.
- Didu kian dd xay ra hien tupng

quang dipn la anh sang chieu tdi
ban kim loai cd budc sdng phai
nhd hon hoac bang mpt gia tri
XQ nao dd.

- Dung cac kinh loc sac F khae nhau
thi thdy ddng quang didn chi xudt hian
khi anh sang chidu vao catdt cd budc
sdng nhd hon hoac bang tri sd XQ.
Vay, didu kian de xay ra hiph tupng
quang dipn la gi ?
- Vdi mpt chum sang don sdc ed budc
sdng

va cd cudng dp sang nhdt

X
dinh thi sy phu thupc eua cudng dp
ddng quang dien I vao hieu dian thd
&^^ ^^^^ ^^ ^^^^^ '^^^ ^^ ^^ ^^
dd thi sau:
UAK

M.
^bh2
^blil

^

-Vu
- Dudng dac tuydn von-ampe
khdng phai la dudng thdng nan
cudng dp ddng dien trong td bao
quang dien khdng tuan theo dinh

luat 6m.
- Khi U^K > Uj, cudng dp ddng
dian gifl gia tri khdng ddi I = Ibh- Khi U^j^ < -Uh thi ddng quang
dian bi triat tiau hoan toan (I = 0).
134

•

O

u,

>

uAK

Cudng dp ddng dien cd tuan theo dinh
luat 6 m khong ? Khi hiau dien thd
UAK ^ ^1 thi cudng dp ddng dien bidn
ddi nhu thd nao ? Cudng dp ddng dian
cd gia tri bang khdng khi nao ?


- Gifl nguyan tri sd cua budc sdng X,

tang cudng dp sang chieu vao catdt va
ve dupe dudng dac tuydn thfl 2. Nhan
xet gi vd sy phu thupc cua ddng If,,, vao
cudng dp chum sang ?

- Cudng dp ddng I^h ti la thuan
vdi cudng do anh sang.

GV bd sung kidn thflc

'

HS t i ^ thu, ghi nhd

- Khi U^K -"^h thi ddng quang dipn
hi triat tiau hoan toan vi: aiectrwi bj bat
ra tfl catdt, vdi tde dp ban ddu VQ^^^^ va
dpng nang ban ddu, da chiu tac dung
eua lye dipn trucmg hudng vd catdt; lye
nay da ngan khdng cho aiectron tdi andt
dd gay ra ddng quang dian. Vi vay,
Uh dupe gpi la hipu dipn thd ham. Tri sd
cua Uf, phu thupc budc sdng X. Nhu
vdy, gifla dpng nang ban ddu cue dai
cua aiectron va dp ldn cua hieu dian thd
ham cd hp thflc :
xiT
... ^^Omax - pTT
"^dmax 2
~

'^

- Ddng dian I^h gpi Id cudng dp ddng
quang dian bao hoa.
Hoat ddng 4
Tim hieu cac dinh luat quang
dian

GV gidi thiau ba dinh luat quang dien
~ Dinh luat vd gidi han quang dian:
Hien tupng quang dian chi xay ra khi
anh sang kieh thich chidu vao kim loai
cd budc sdng nhd hon hoac bang budc
sdng XQ, XQ duac gpi la gidi ban quang
dian cua kim loai dd : XQ< X.

135


HS chu y ldng nghe va ghi nhd

- Dinh luat ve cudng dp ddng quang
dien bao hoa : Ddi vdi mdi anh sang
thich hpp (cd ^o - ^ ) ' cudng dp ddng
quang dien bao hoa ti le thuan vdi
cudng dp cua chum sang kieh thieh.
- Dinh luat vd dpng nang eye dai cua
quang aiectron : Dpng n ^ g ban ddu eye
dai eua quang aiectron khong phu thupc
vao cudng dp eua chum sang kieh thich,

md ehi phu thupc budc sdng anh sang
kich thieh va ban ehdt cua kim loai.

HS thao luan ehung toan ldp
- Dinh luat quang dien thfl nha't
dupe rut ra tfl ket qua thi nghiem
ddu tian : Didu kian dd xay ra hien
tupng quang dian la anh sang
chia'u tdi ban kim loai ed budc
sdng phai nhd hon hoac bang mpt
gia trj XQ nao dd.

GV yau cdu HS tra ldi eau hdi sau de
tim hieu eac djnh luat quang dien
- Cac djnh luat quang dipn tran dupe rut
ra tfl ket qua thi nghipm nao ?

- Dya vao dudng dac trung vdnampe ta tha'y ddng quang dien bao
hoa ti la thuan vdi cudng dp chum
sang kich thieh. Ke't qua thi
nghiam nay eho phep ta suy ra
dinh luat quang dien thfl hai.
- Theo ka't qua thi nghiem tran ta
tha'y: Trj sd cua U,, phu thupc
budc sdng X.
_
Mat khae W,dmax _"IXOmax =
eU„

va vdi mdi kim loai thi cd mpt gidi

ban quang dien nhat djnh nan ta
suy ra dinh luat quang dian thfl 3.
136


Hoat ddng 5
Cung cd bai hpc va dinh hudng
nhiem vu hpc tap tiep theo

GV nau cau hdi cung c6 bai hpc
- Hay chflng td ring, ba djnh luat quang
dien bao ham dupe tat ca kdt qua thi
nghiem tran.
- HS ve nha lam cae bai,tap 1, 2, 3, 4, 5
SGK.
- On lai cac kien thflc da hpe bai 43
SGK va cac khai niam hat, sdng.

137


BAI44

THUYDT LUONG TtT A N H SANG
LUQNG T I N H SONG - HAT CUA A N H SANG
I-MUCTlfiU
1. ve' kigh thflc
- Neu dupe npi dung co ban cua gia thuyet lupng tfl cua Piang va thuydt
lupng tfl anh sang eua Anh-xtanh.
- Vidt dupe cdng thflc Anh-xtanh vd hian tupng quang dien ngoM.

- Nau dupe anh sang cd ludng tinh sdng-hat.
- van dung dupe thuydt lupng tfl anh sang dd giai thich ba dinh luat quang dian.
2. Ve ki nSng
- Ren luyen ki nang giai thich cac hian tupng vat li.
- Ren luyen ki nang van dung cdng thiic Anh-xtanh vd hian tupng quang dian de
giai thieh eac dinh luat quang dien va lam mdt sd bai tap.
~ Ren luyen ki nang suy luan Idgic trong viec dp dung thuydt lupng tfl anh sang dd
giai thieh eac djnh luat quang dien.
- Ren luyan ki nang lam bai tap trdc nghiem khach quan nhidu lua chpn vd phdn
thuyet lupng tfl anh sang.

II-CHUXNBI
Gido vien
- Chudn bj phia'u hpc tap cho HS.
Hpc sinh
- On lai cae kidn thflc da hpc bai 43 SGK va cac khai niam hat, sdng.

138


m - THifiT K £ ' HOAT D 6 N G DAY HOC
Hoat ddng cua hoc sinh

Trp giup cua giao vi^n

Hoat ddng 1
Kidm tra, chuan bi dieu kien
xuat phat. Dat van dd.
HS suy nghl ca nhan tim eau tra ldi
- Theo thuyet dipn tfl vd anh sang,

cudng dp chum sang kich thich
cang ldn, thi dian trudng bidn thian
trong anh sang cang manh, lam
cho aiectron trorlg kim loai dao
dpng cang manh, tde dp va dpng
nang cua aiectron cang ldn. Hian
tupng quang dipn se xay ra khi
dpng nang cua aiectron dat dupe
gia trj du ldn de aiectron bflt ra
khdi bd mat kim loai. Vay theo
thuydt lupng tfl anh sang, mudn
hian tupng quang dian xay ra thi
cudng dp 6hum sdng kich thich
phai ldn hon mpt gidi ban nao dd;
draig nang cua aiectron quang dien
phu thupc vao cudng dp chum
sang kich thich. Ket luan nay mau
thudn vdi cac dinh luat quang dien.

GV nau cau hdi kidm tra kien thflc cu
- Sfl dung thuydt dian tfl dd giai thi'eh
cac dinh ludt quang dian.

Ddt vdn de : Ta da biet, dung thuyet
dian tfl vd anh sang khong giai thich
dupe cae dinh luat quang dipn. Mudn
giai thieh dupe cae dinh ludt quang dian
ta edn phai sfl dung mpt tinh chdt khdc
eua anh sang ma khdng phai la tinh chdt
sdng. vay tinh chat dd la gi? Bai hpe

ngay hdm nay giup ehung ta tra ldi eau
hdi dd.
139


Hoat ddng 2
Tim hieu thuyet lupng tfl anh sang

HS chu y ldng nghe

GV gidi thiau vd gia thuydt lupng tfl
nang lupng cua Plang
- Nam 1900, nha vat li ngudi Dfle Plang
da dd xudng gia thuydt ve lupng tfl nang
lupng nham giai thich sy phat va ha'p
thu bfle xa cua cae vat, dac biat la cae
vat ndng sang.
- Theo Plang thi lupng nang lupng ma
mdi lan mpt nguyen tfl hay phan tfl hdp
thu hay phat xa cd gia tri hoan toan xac
dinh, gpi la lupng tfl nang lupng. Lupng
tfl nang lupng, ki hieu la e, cd gia tri
bang: 8 = hf.
Trong dd f la tdn sd eua anh sang bi
hdp thu hay dupe phat ra ; h la mpt
hang sd, gpi la bang sd Plang, h =

HS tiep thu, ghi nhd

6,625. lO-^'^J.s.

GV gidi thieu npi dung thuyet lupng tfl
anh sang
- Nam 1905, dd giai thieh dinh luat
quang dian, nha bac hpc Anh - xtanh,
da phat tridn gia thuyet cua Plang lan
mpt budc va dd xudt thuyet lupng tfl anh
sang (cdn gpi la thuyet phdtdn). Ndi
dung cua thuyet lupng tfl anh sang:
1. Chum anh sang la mdt chum eac
phdtdn (cae lupng tfl anh sang). Mdi
phdtdn ed nang lupng xa djnh e = hf (f
la tdn sd cua sdng anh sang don sac
tuong flng). Cudng dp cua chum sang ti
la vdi sd phdtdn phat ra trong 1 gidy.
2. Phan tfl, nguyan tfl, aiectron... phat
xa hay hdp thu anh sang, cung cd
nghia la ehung phat xa hay hdp thu
phdtdn.

140


3. Cae phdtdn bay dpc theo tia sang vdi
tde dp c = 3.10 m/s trong chan khdng.
HS lam viec ea nhan tim cau tra ldi
- Ap dung cdng thflc :
e = hf = h X
6,625.10-^^3.10^
0,75.10 - 6

2,65.10-'^:^

- Na'u chum sang la don sdc dd thi
cd mpt loai phdtdn flng vdi anh sang
dd cd budc sdng X = 0,76|am.

GV yau cdu HS tra ldi cac cau hdi sau
de hidu vd thuydt lupng tfl anh sang
- Hay tinh nang lupng cua phcton flng
vdi anh sang dd cd bude sdng
X = 0,15\im.

- Trong chum sang mau dd cd may loai
phdtdn ?

- Neu chum sang mau dd cd eae
budc sdng >. = 0,640^ 0,750pm thi
cdvosd phdtdn.
Hoat ddng 3
Ap dung thuyet lupng tiir anh
sang de giai thich cac dinh luat
quang dien
HS thao luan ehung toan ldp
- Nang lupng 8 cung cdp cho
aiectron dupe sfl dung dd : eung
cdp cho aiectron mpt cdng de nd
thoat ra khdi bd mat kim loai,
truyen cho nd mpt dpng nang ban
ddu va truyen mpt phdn nang
lupng cho mang tinh the.

- Khi aiectron ndm ngay tran be
mat tinh the.
Ap dung djnh luat bao toan nang
lupng, ta cd :

GV nau eau hdi de HS tim hidu cdng
thflc Anh - xtanh vd hien tupng quang

dian
- Trong hien tupng quang dien, gia sfl
electron trong kim loai hdp thu hoan
toan photon cua anh sang kich thich.
Nang lupng nay dupe dung de lam gi ?
- Khi nao thi aiectron thoat ra khdi bd
mat kim loai va ed dpng nang cue dai?
- Gpi A la cong cdn cung cap cho
aiectron d bd mat kim loai, ap dung djnh
luat bao toan nang lupng ta ed bidu thflc
nhu the nao ?

hf = A + mv Omax

141


GV thong bao
- Cdng thflc bf = A + ^ ^ ^ ^ ^ la edng
thflc Anh-xtanh vd hien tupng quang dian.

HS thao luan ehung toan ldp

GV nau eau hdi dd HS giai thieh cdc
dinh luat quang dien
- Sfl dung thuydt lupng tfl anh sang va
edng thflc Anh-xtanh vd hipn tupng
quang dien de giai thich ba djnh luat
quang dian ?

- Theo cdng thflc
2

hf = A + ^^^Q"'^. mudn eho hian
2
tupng quang dian xay ra, nghia la
mudn eho aiectron bat ra khdi bd
mat kim loai dung lam catdt, thi
phdtdn cua anh sang chieu vao catdt
phai cd nang lupng :

GV nau cau hdi gpi y
- Mudn eho aiectron bat ra khdi bd mat
tdm kim loai dung lam eatot thi nang
lupng cua phdtdn dnh sang chidu vao cd
gia tri nhd nhdt bang bao nhiau ?

X
A
^
he
vay XQ= — chinh la gidi ban

quang dien cua kim loai lam catdt.
- Cudng dp eua ddng quang dian
bao hoa ti le thuan vdi sd quang
aiectron bdt ra khdi catdt trong mot
don vi thdi gian. Vdi cac chum
sang cd kha nang gay ra hipn
tupng quang dien, thi sd quang
aiectron bi bat ra khdi mat catdt
trong mpt don vj thdi gian lai ti la
thuan vdi sd photon den dap
vao mat catdt trong thdi gian dd.
142

- Cudng dp ddng quang dipn bao hod
phu thupc nhu thd nao vao sd aiectron
quang dian trong mpt don vi thdi gian ?
- Sd aiectron bi bat ra khdi bd mat catdt
phu thupc nhu the nao vao cudng dp
chum sang kich thich ?


Sd phdtdn nay ti la vdi cudng dp
eua chum sang tdi. Tfl dd suy ra,
cudng dp eua ddng quang dipn bao
hod ti le thuan vdi cudng dp eua
chum sang chia'u vao catat.
- Ta cd :
hf

- Dya vao cdng thflc Anh-xtanh vd hian

tupng quang dien, hay eho biet dpng
nang eye dai ban ddu phu thupc vao
nhflng yeu td nao ?

A + "'''Omax
2

_j mv^^g^ _ he

^

2
X
Suy ra dpng nang eye dai ban
ddu phu thupc vao budc sdng ciaa
anh sang kieh thich vd ban chdt
kim loai dung lam catdt.
Hoat ddng 4
Tim hieu luong tinh sdng hat cua
dnh sang

GV nau cau hdi dd HS hieu ro ludng
tinh sdng hat eua anh sang

HS thao luan ehung toan ldp

- Chung ta da hpc nhflng tinh chat nao
cua anh sang ?

- Ngudi ta sfl dung tinh ehdt sdng

ciia dnh sang de giai thich hian
tupng giao thoa.
- Ngudi ta sfl dung tinh chdt hat
cua dnh sang dd giai thich hian
tupng quang dian.
- Anh sang ed budc sdng cang ldn,
phdtdn flng vdi nd cd nang lupng
cang ldn. Anh sang thd hipn rd tinh
chdt hat nhu d hian tupng quang
dian. kha nang ddm xuyan ldn, lam
phat quang... NgUpe lai anh sang
cd budc sdng cang dai thi tinh chdt
sdng thd hien cang rd.

- Ngudi ta sfl dung tinh chdt sdng cua
anh sang de giai thieh hidn tupng gi da
hpc?
- Ngudi ta sfl dung tinh chdt hat cua anh
sang dd giai thieh hian tupng gi da hpe ?
- Tinh chat sdng cua dnh sang thd hian rd
khi anh sang cd budc sdng nhu thd nao ?
- Tinh chdt hat eua anh sang the hian ro
khi anh sang cd budc sdng nhu the* nao ?

143


GV the che hoa kidn thflc
- Nhu vay, anh sang vfla cd tinh chat
sdng, vfla ed tinh ehdt hat. Ngudi ta

ndi rang, anh sang ed ludng tinh
sdng-hat.
- Trong mdi hien tupng quang hpc, anh
sang thudng thd hien ro mpt trong hai
tinh cha't tran. Khi tinh eha't sdng thd
hien ro, thi tuih ehdt hat lai md nhat, va
ngupe lai.
Hoat ddng 5
Cung cd bai hpc va dinh hudng
nhiem vu hpc tap tie'p theo

GV yau cdu HS lam bai tap trong phia'u
'hpe tap dd eung cd bai hpc
- HS vd nha lam cae bai tap 4, 5 SGK.

PHI^U HOC TAP
Cau 1. Chpn cum tfl thich hpp didn vao d trdng
Theo gia thuyet lupng tfl cua Plang thi nang lupng eua
ludn bang mpt sd nguyan lan lupng tfl nang lupng.
A. mpi aiectron.
B. mpi nguyan tfl.
C. phan tfl eua mpi ehdt.
D. mpt chum sang don sdc.
Can 2. Theo thuyet phdtdn eua Anh-xtanh, thi nang lupng
A. ciaa mpi phdtdn ddu bang nhau.
B. eua mpt photon bang mpt lupng tfl nang lupng.
C. giam ddn, khi phdtdn cang rdi xa ngudn.
D. cua photon khdng phu thupc budc sdng.
Cau 3. Cong thflc Anh-xtanh vd hian tupng quang dian la
A. hf = A +

mvl

C. hf ^"'^Q'^^-A.
2
144

B. hf = A + "IVomax
^ he he mv
D. ^A, + ^A/ = ——

phai


BAI45

BAI TAP Wt mfiN TUONG QUANG DifiN
l-MUCTl£u

/'-:'•'

1. Vi kie'n thflc
- Ndm ehdc va bidt van dung edng thflc Anh-xtanh va eac cong thflc khae ed
lian quan den hian tupng quang dian dd giai thich cac bai tap vd hian tUpng
quang dien.
2. Ve kl nSng
- Ren luyen ki nang tinh toan bang sd (chuydn ddi don vi, lam trdn sd cd
nghia...).

II-CHUXNBI

Gido vien
- Oiudn bi phieu hpe tap cho HS.
Hpc sinh
- 6n tap lai kia'n thflc bai 43 va 44.
Ill - THifiT K£' H O A T

D6NG

DAY HOC

Hoat ddng cua hpc sinh

Trp giup cua giao vi^n

Hoat ddng 1
Kiem tra, chu^n bj dieu kien
xua't phat
HS suy nghi ea nhan tim cau tra ldi

TKBG VLyi2a(NC)

GV nau cau hdi kidm tra kien thflc cu
- Via't cdng thflc Anh-xtanh vd hian
tupng quang dian?
- Phat bieu ba djnh luat quang dien.
- Phat bidu thuyet lupng tfl anh sang
ciaa Anh-xtanh.
145

Hoat ddng 2
Lam bai tap 1 de biet each van
dung cong thflc Anh-xtanh va
cac cong thflc cd lien quan vd
hien tupng quang dien
HS lam bai tap theo nhdm, sau dd
dai dien nhdm lan bao cao kdt qua

GV yau cdu HS lam bai tap 1 trong
phia'u hpc tap theo nhdm, sau dd dai
dien nhdm lan bao cao kdt qua.

a) Ta ed Xn = —
GV ndu cac cau hdi gpi y
" A
Biet h = 6,625.10"^"* j.s ; c = 3.10^ m/s - Gidi han quang dian cua kim loai
dung lam catdt dupe tinh theo edng thflc
A = 2,15eV= 3,44.10"'^J.
nao?
Tfl dd, tinh dupe : XQ « 0,578 pm.
b) Ap dung cdng thflc Anh-xtanh :
— = A+ "IVomax
X

^Omax

, t a CO r

- Sfl dung bidu thflc nao dd ed thd xac
djnh dupe van tde ban ddu eye dai ciia

aiectron quang dien ?

m X

Thay sd, ta dupe :
V0max'**3,7.10^m/s.

he
c)Tacd:eUh=^^^^^^^= — - A ,

Ne'u y nghia cua hiau dipn thd ham.

tfldd :Uh = e X
Thay sd (e = 1,6.10"'^C), ta
dupe: Uh= 0,39 V.
d) Nang lupng mdi phdton la:
8 = -=4,06.10-'^J
X

146

- Mudn tinh dupe hiau sudt lupng tfl ta
cdn phai xac dinh dupe nhiing dai lupng
nao?


Sd hat phdtdn tdi catdt mdi giay:

— 1

N=—«3,08.10'^hat
e
Guong dp ddng quang dian bao
hoa l^h = ne, vdi n la sd aiectron

- Cdng sudt eua chum sang cd lian he
nhu the nao ddi vdi sd phdtdn N eua
chum sang chieu tdi be mat kim loai
trong I gidy?

bflt ra khdi mat kim loai va
chuydn vd andt trong mpt don vj
thdi gian. Tfl dd :
•

n=^

=3,12.10*^ hat
e
Hieu sudt lupng tfl :

- Na'u tinh dupe sd quang aiectron bflt
ra trong mdt giay va sd phdtdn tdi be mat
kim loai trong mpt giay thi cd thd xac
djnh dupe hiau sudt lupng tfl khdng ?

- Cucmg dp ddng quang didn bao boa
lian ha nhu the nao dd'i vdi sd quang
aiectron trong 1 giay ?

H = -^«ilO"^=l%
N
Hoat ddng 3
Van dung dieu kien xay ra hien
tupng quang dian de lam bai tap 2
HS lam bai tap theo nhdm, sau dd
dai dien nhdm lan bao cao ket qua
Ap dung cdng thflc Anh-xtanh ta
ed :
. he 1 2
A=Y--mvo^^
Thay sdtadupe: A=1,94.10"'^L
Gidi han quang dian cfla tam kim
loai :

GV yau cdu HS lam bai tap 2 trong
phia'u hpc tap theo nhdm, sau dd dai
dien nhdm lan bao cao ket qua.

GV nau eac eau hdi gpi y
- Didu kien de xay ra hien tupng quang
dian la gi ?
- Mudn biet hai chum sang chidu tdi i
ta'm kim loai cd gay ra hien tupng quang
dian hay khong ta cdn phai xae dinh
dupe dai lupng nao ?
- Mudn xae djnh dupe gidi ban quang i

A,Q = i ^ = 1,02.10"^ m = 1,02Hm
A

Mudn ed hidn tupng quang dien
xay ra, budc sdng X eua anh
sang kich thich phai thoa man
didu kian X < XQ. DO do :

dien XQ ta phai xae djnh dupe dai lucmg i
nao ? Sfl dung cdng thflc nao de xac
djnh dupe dai lupng dd ?

147


- Vdi X] thi A.] > XQ ndn hien
tupng quang dian khdng xay ra;
- Vdi X2 thi X2tupng quang dien xay ra. khi dd,
dpng nang ban ddu eye dai eua
aiectron bdn ra la :
EXom-=]^_A«l,79.10-'«J.
2
X2
Tfldd :voniax ^1.98.10^ m/s.
Hoat ddng 4
Tim hieu khai niem he quy chidu
va chuyen dpng tinh tien
HS lam bai tap theo nhdm, sau dd
dai dien nhdm lan bao cao kdt qua

GV yau cdu HS lam bai tap 3 trong
phidu hpc tap theo nhdm, sau dd dai

dien nhdm lan bao cao ket qua.

a) Gidi ban quang dien eua ddng :

GV nau cac cau hdi gpi f

he — 6,625.10"^'*.3.10^
?^
4,47.1,6.10-19

X{\ — —

^-6

=«0,278.10"°mft=278nm.
b) Ap dung cdng thflc Anh-xtanh
ta cd:
— = A + mvOmax
X
mVomax

7,044.10"'^J

Omax

1,244.10^ m/s.

148

- Tai sao qua cdu tich dien ?

- Dien the cua qua cdu phu thupc nhu
the nao vao sd electron bj bat ra khdi b^
mat qua cdu ?
- Theo thdi gian, didn tich eua qua cdu
tang thi dian thd eua qua cdu bien ddi
the nao ? Lieu cd thd tang mai khdng ?
- Khi nao dien the cua qua cdu khdng
tang nfla ?
- Gia trj dien the eye dai cua qua cdu
chinh la dai lupng nao trong te bao
quang dian ?


Ban ddu, qua cdu chua tich dian.
Khi chia'u bfle xa cd budc sdng
X vao qua cdu thi aiectron bj bflt
ra khdi mat qua cau va qua cdu
tich dien duong, qua cdu cd mdt
dian the. Sd aiectron bj bflt ra
khdi mat qua cdu ngay cang
nhidu, dien thd cua qua eau tang
ddn va khi dien thd cua qua cdu
dat tdi gia trj V^^ thi cac
aiectron vfla mdi blot ra tham lai,
lai bj hut trd lai qua cdu, va dian
the cua qua cdu khdng tang nfla.
vay gia trj eye dai V^ cua dipn
the qua cdu chinh la hieu dien
the ham trong td bao quang dien.
Do dd, ta ed :

eV„=eUK
=
m

mvoniax

Tfl do, suy ra :
e

2

7,044.10

-19

« 4,40 V

1,6.10'
c) Theo tran ta cd :
gy =EXomax_, 6day V^ = 3 V .
m
2
Tfldd:
2eV
^Omax

1,03.10^ m/s.

- Dya vao cau b ta ed the tinh van tde
eye dai ban ddu cua quang aiectron nhu

thd nao ?
- Mudn xac dinh budc sdng cua anh
sang kich thieh ta phai ap dung cdng
thflc nao ?

Ap dung cdng thflc Anh-xtanh :
ll^ = A + ^ ^ ^ ^ = A + eVm'
X
2
149


suy ra :
^^^ he
_ 6,625.10-^^3.10^
A + eV^ (4,47 + 3)1,6.10-'^
mwl66nm.
PHl£u H p c TAP
cau 1. Chia'u mpt chum anh sang ed budc sdng X = 0,489ta,m lan mpt tdm
kim loai kali dung lam catdt cfla mpt te bao quang dien. Bidt cong
thoat aiectron cua kali la 2,l5eV.
a) Tinh gidi ban cua kali.
b) Tinh van tde ban ddu eye dai cua aiectron bdn ra tfl catdt.
c) Tinh hieu dien the ham.
d) Bia't cudng dp ddng quang dien bao hda I^h =5mA va cdng sudt cua
chum anh sang chidu vao catdt la S!^=1,25W, hay tinh hiau sudt
lupng tfl (ti sd gifla sd aiectron bflt ra khdi mat kim loai va sd
phdtdn tdi mat kim loai).
cau 2. Khi chia'u vao mpt tdm kim loai mdt chum sang don sdc cd budc song
0,2}am,dpng nang ban ddu eye dai cua aiectron quang dien la

S.IQ-'^J. Hdi khi chia'u vao tdm tim loai dd ldn lupt hai chum sdng
don sac cd budc sdng Xi=l,40|am va X2 =0,10|am, thi cd xay ra hien
tupng quang dien khong ? Ndu cd, hay xac djnh van tde ban ddu cue
dai cua cac aiectron quang dien.
cau 3. Cdng thoat cua aiectron khdi ddng la 4,47eV
a) Tinh gidi han quang dien eua ddng.
b) Khi chia'u bfle xa cd budc sdng ^=^ 0,14pm vao mot qua cdu bdng
ddng dat xa cac vdt khae thi qua cdu dupe tich dian den dien thd
eye dai la bao nhieu ? Van tde ban ddu eye dai cua aiectron quang
didn la bao nhiau ?
c) Chia'u mpt bfle xa didn tfl vao mdt qua cdu bang ddng dat xa cac vat
khae thi qua cdu dat dupe dipn the eye dai 3V Hay tinh budc sdng
cua bfle xa va van tde ban ddu eye dai cua aiectron quang dipn.
150


BAI46

QUANG DifiN TRONG
QUANG DifiN T R 6 VA PIN QUANG DifiN
H I £ N TT/ONG

I-MUCTlfiU
1. va' kie'n thflc
- Dinh nghia dupe hipn tupng quang dian trong.
- van dung de giai thich dupe hien tupng quang ddn.
- Trinh bay dupe djnh nghia, cdu tao cua quang trd va pin quang dipn va hoat
ddng cua pin quang dien.
- Dy doan dupe vdi cac cudng dp chum sang khae nhau se cho gia tri cudng
dp ddng dian khae nhau.

- Dd xudt phucmg an thi nghiam dd kidm tra dupe dy doan : Thay doi cudng
dp chum sang dpc gia trj cua cudng-dp ddng dian tuong ihig.
2. va' ki n5ng
-

Ren luyan ki nang dua ra dy doan ddi vdi mpt hian tupng vat li.
Ren kl nang lap mach dian.
Ren luyen ki nang quan sat, xfl ly thdng tin thu thap dupe:
Ren luyen kT nang tim hieu cae ung dung ki thuat vat li.

n-CHuXNBI
Gido vien
- Bp thi nghiem bidu didn vd hian tupng quang dian trong va cac flng dung.
- Bp thi nghiem flng dung sfl dung quang trd trong he thdng ddng ngdt den dudng.
- 4 bp thi nghiam khao sat hien tupng quang dipn trong va cac flng dung.
Hpc sinh
- 6n lai cac kia'n thflc vd ddng dien trong chdt ban ddn trong chuong trinh vat li 11
nang cao va eac bai 43 va 44 SGK vat U 12 nang cao.

151


Ill - THlfiT Kfi HOAT © O N G DAY HOC
Hoat ddng cua hoc sinh

Trp giup cua giao vi§n

Hoat ddng 1
Kiem tra, chuan hi dieu kien
xuat phat. Dat van de

HS suy nghl ca nhan tim cau tra ldi

GV nau eau hdi kidm tra kia'n thflc cu
- Trinh bay hian tupng quang dian
ngoai va giai thieh hipn tupng?
- Phat bidu ba djnh luat quang dian va
sfl dung thuydt lupng tfl anh sang ciia
Anh-xtanh dd giai thich ba djnh ludt
quang dipn.
Dat vdn de : Pin Mat Trdi cung cdp dian
nang cho Tram Nghian cihi vu tru qudc
td ISS boat dpng dya tren hian tupng
nao ? Bai hpc nay giup chflng ta tra ldi
cdu hdi dd.

Hoat ddng 2
Tim hidu hien tupng quang dien
trong

HS quan sat GV tidn hanh thi
nghiem

GV tien hanh thi nghiam lam nay sinh
vdn dd cdn nghian cihi.
- Lam thi nghiam thdy hipn tupng la khi
chidu anh sang vao linh kipn ban dan thi
thdy ed ddng trong mach, khi khdng
chia'u anh sang vao thi khdng cd ddng
trong mach.

- Dung cu dd cd dac tinh la khi chidu
sang thi cd ddng chay qua, khi khdng
chia'u sang thi khdng cd ddng chay qua.
Ngudi ta gpi dung cu nay la quang trd.
~ Trong thyc ta' ed mpt sd chdt ban din
nhu: Ge, Si, PbS, PbSe, PbTe, CdS,
CdSe, CdTe... cd tinh chat dac bipt nhu
vay gpi la tinh quang ddn.

152


HS thao luan ehung toan ldp

Vdn dd cdn nghian cflu : Tai sao khi
chia'u anh sang vao quang trd thi
quang trd ddn dipn, khi khdng chidu
anh sang vao thi quang trd khdng dan
dien.

- Dieu kian dd cd ddng dien la
trong mach phai cd:
+ Dien trudng (Hieu dien tha")
+ Hat tai (Hat mang dien)
- Trong hai trudng hpp da cd dian
trudng, trudng hpp chidu sang da
cd hat tai dien thi trong mach mdi
cd ddng dien.
- Khi chia'u anh sang vao quang trd,
mdi phdtdn anh sang kich thieh se

truydn toan bp nang lupng eua nd
eho mpt electron lian kdt, lam giai
phdng khdi mdi Uan kdt dd trd thanh
electron din va 16 trdng tham gia
vao qua trinh ddn dipn.
HS thao luan ehung toan ldp dua ra
dydoan
- Na'u tang cudng dp chum sang
till cudng dp ddng dian chay trong
mach se tang.

GV nau eac cau hdi gpi y
- Didu kian de cd ddng dien la gi ?
- Cac em quan sat trong ca hai trudng
hpp cd anh sang va khOng cd anh sang
chieu vao da cd didu kian nao rdi ?
- Sy khae nhau d chieu sang va khdng
chia'u sang la gi ?
- Liau cd phai anh sang cung cd vai
trd gidng nhu hian tupng quang dien
ngoai ma ta da biet khdng.

- Tang cudng dp chum sang bang
each giam khoang each tfl ngudn
sang tdi quang trd, do cudng dp
ddng dien tuong flng.

GV nau cau hdi vd vdn dd cdn nghidn
cflu tia'p
- Ndu gia thuydt tran ma dung thi

cudng dp chum sang ed anh hudng dah
cudng dp ddng dien trong mach khdng ?
GV nau cdu hdi thidt kd phuong an thi
nghiam kiem tra du doan
- Vdi bp thi nghiam vfla tidn hanh
lam the nao dd kiem tra didu nay?
GV nau cau hdi gpi y
- Cdn phai tien hanh thi nghiem nhu
the nao?
- Thay ddi cudng dp chum sang bdng
each nao ?
153


- Co thd thay ddi cudng dp chum
sang chia'u ldi quang trd bang each
thay ddi khoang each tfl ngudn saiig
tdi quang trd dupe khdng ?
HS lam thi nghiem theo nhdm, sau
dd dai dien nhdm lan bao cao ket
qua

*^^' yau cdu HS chia ldp thanh 4
nhdm thi nghiam, mac so dd mach
dien nhu hinh ve sau vd tien hanh thi
nghiem kidm tra

Ket qua thi nghiem : Vdi cae
cudng dp chum sang khae nhau se
eho mpt gia trj cua cudng dp ddng

dien. Tang cudng d6 chum sang
chia'u tdi quang trd thi cudng dp
ddng dien tang.

V

GV thdng bao
- Hien tupng tao thanh cac aiectron dan
va 16 trdng trong ban dan, do tac dung
eua anh sang ed budc sdng thich hpp,
gpi la hien tupng quang dien trong.
- Mudn gay dupe hien tupng quang
dien trong thi anh sang kich thich phai
HS tia'p thu, ghi nhd

cd bude sdng nhd hon hoac bdng nipt
gia trj ^Q, gpi la gidi han quang dian
ciaa ban ddn.
- Vl nang lupng cdn thidt dd giai phdng
aiectron lian kdt trong ban ddn thudng
nhd hon cdng thoat A cua electron tir
mat kim loai nan gidi ban quang dien
cua nhidu ban ddn nam trong vung anh
sang hdng ngoai. (Thang ban vdi Ge thi
XQ

154

= l,88^im, vdi Si thi XQ=1,1 1pm...