1.

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

Answer»

Will be larger than the earlier value.
Will be the same as the earlier value
Will be less than the earlier value
Will depend on the target

Solution :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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