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

Answer

C

Explanation

In Davisson-Germer experiment, the de-Broglie wavelength associated with electron is
`lamda = (12.27)/(sqrtV)Å" "...(i)`
where V is the applied voltage
If there is a maxima of the diffracted electrons at an angle `theta` , then
`2d sin theta = lamda " "...(ii)`
From Eq. (i) we note that if V is inversely proportional to the wavelength `lamda`
i.e., V will increase with decrease in `lamda`
From Eq. (ii), we note that wavelength `lamda` is directly So, with decreases in `lamda, theta` will also decrease
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.