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Consider arrangement shown In figure for davisson-Germer experiment when voltage applied to A is increased in diffracted beam will have maximum number of electron for value diffraction angle `(theta)` such that…..

A

Will be larger than the earlier value.

B

Will be the same as the earlier value

C

Will be less than the earlier value

D

Will depend on the target

Text Solution

Verified by Experts

The correct Answer is:
C
In the present case ,Path diffrence between matter waves diffracted from the onsecutive atomic layers of targer element,separated by perpendiular distance d is equal to 2dsin`theta` (where `theta`=angle of diffraction).
Now ,as per the statement,for no.Of electrons getting diffracted at angle `theta` to become maximum,value of matter wavelength of moving electrons.`lambda` should be such that it can satisfy the condition of constructive interference.
Thus ,2din `theta lambda`
`therefore` 2din `theta=n((h)/(sqrt(2Vem)))`
`implies` As V increases, sin`theta` decreases and so `theta` will also decrease.
Second method:
In Dacisson-Germer experiment let voltage applied to andoe is V.De-Broglie wavelength assocaited wth electron,
`lambda=(12.27)/(sqrt(V))Å`.......(1)
For electron diffracted at angle `theta` condition for central maximum `lambda-2dsintheta`.......(2)
From equation (1) if V increase then `lambda` will decrease and from equation (2) in `lambda` decrease then `theta` will also decrease.
(For samll angle of diffraction sin`theta~~theta`).
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