A parallel beam of electrons travelling in x-direction falls on a slit of width d (see figure). If after passing the slit, an electron acquires momentum `p_y` in the y-direction then for a majority of electrons passing through the slit (h is Planck's constant):

Options

A. `|P_y|d gt h`
B. `|P_y| d lt h`
C. `|P_y|d = h`
D. `|P_y| d gt gt h`

Answer

A

Explanation

From bragg.s equation
`d sin theta = lamda`
`sin theta = lamda/d lt 1`
`therefore lamda lt d`
`(h)/(|p_y|) lt d [ because (h)/(|p_y|)]`
` therefore h lt |p_y| d `