Consider figure. Suppose the voltage applied to A is increased. The diffracted beam will have the maximum at a value of `theta` that

Options

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

Explanation

In Davisson-Germer experiment the de-Broglie wavelength associated with electron is
`" "lamda=(12.27)/(sqrtV)Å`
where V is the applied valtage.
If there is a maxima of the diffracted electrons at an angle `theta,` then
`" "2dsintheta=lamda`
From Eq. (i). we note that if V is inversely proportional to the wavelength `lamda.` i.e., V will increase with the decrease in the `lamda.`
From eq. (ii), we note that wavelength `lamda` is directly proportional to `sintheta` and hence `theta.` So, with the decrease in `lamda,theta` will also decreases.
Thus, when the voltage applied to A is increased. The diffracted beam will have the maximum at a value of `theta` that will be less than the earlier value.