Direction of the first secondary maximum in the Fraunhofer diffraction pattern at a single slit is given by (a is the width of the slit)

Options

A. `a sin theta=lambda/2`
B. `a cos theta=(3lambda)/2`
C. `a sin theta=lambda`
D. `a sin theta=(3lambda)/2`

Answer

D

Explanation

In single slit, for nth secondary maxima path difference
`a sin theta=(2n+1)lambda/2`
for first secondary maxima `n=1`
`:. a sin theta=(3lambda)/2`