IIT JEE , AIEEE Forum - Chemistry , Physical Chemistry - Compton effect-concept..rates assured

learner

From Compton effect we have the formula :

dl = h (1 - cos @ )/ m_ec...

where dl is change in wavelength,

h is Plancks constant,

@ is angle of scattering of photon,

c is veolcity of light..

My doubt is this sentence :

"Thus, scattered wavelength is always greater than the incident wavelength.This provides convincing evidence of quantum nature of radiation ."

How???

Rates assured!

Thanks!

budokai_tenkaichi_returns

gud question

cutepooja

do u mean how it proves photon concept of electron

cutepooja

hey

the compton theory used the quantam concept and particle nature of photon laws of conservation of energy and momentum applied to point like scattering of photon from electron was the proof i can give details if u want

cutepooja

am i correct

learner

I meant how does it prove quantum nature of radiation, as opposed to the classical picture?

cutepooja

do u want the proof i can give

shreyasnivas

higher wavelenght means lower energy.

imagine electrons in n = 1 state. (maximum amount of electrons here). it will absorb a photon only of certal energy, so that it can go EXACTLY to any integral higher state. suppose it goes to n = 3.

from here, it comes back to n = 1. but not directly. some amount of electrons will go directly, some go to n = 2 and then to n =1 .

the few electrons who go from n = 3 to n = 2 will cause a high wavelneght photon to be emitted.

the electrons who were not in n= 1 to begin with are a very very small amount, so their contribution is negligible.

you mey not consider my explanation as good enough.. but this is true.. i had asked my sir some time ago.

cheers

shreyas

learner

I want to know how the fact that scattered wavelength is greater than incident wavelength proves quantum nature of radiation.

@cutepooja - if the proof explains THIS,please give it !

Thanks!!

cutepooja

classical theory says when a photon interacts wid electron the electrons oscillate wid freq of photon as the interaction radiates em radiation at this freq (thomson scatterin)
at backward scattering angles there appeared a component of emiited rad (modifeid wave) had a longer wavelength than unmodified
the classical theory cud not explain that

cutepooja

wait i am writin further but pls guide me am i goin correct

shreyasnivas

o ya n the quantum theory.. well, the electron wud not go from n = 3 to n =2 to n =1 unless these quantum states existed in the first place... i agree the statement is slightly vague.. probably they are mentioning in context to something they wrote before this also?

paulparthapratim2

Light must behave as if it consists of particles in order to explain the Compton scattering. Compton's experiment convinced physicists that light can behave as a stream of particles whose energy is proportional to the frequency.

learner

@cutepooja- pl. go on..I think I'm understanding something

@shreyasnivas -before this the only thing is Compton effect itself-the description..could that be it?Thanks for your answer!!I partly understood!

cutepooja

momentum at the speed of lite
p=e\c=hv\c=h\lambda
the photon was treated as particle wid definite energy
let scattering take place in xy plane
so momentum must be conserverd in x and y both
elecrtons total energy is related as
Ee(square)=(mc2)2+ p(electron)2c2
from conservation of energy
hv+ mc2 = hv' +E e
from law of cons of momentum contd

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