Light is incident normally on a diffraction grating through which the first order diffraction is seen at `32^@`. The second order diffraction will be seen at

Options

A. (a) `48^@`
B. (b) `64^@`
C. (c) `80^@`
D. (d) There is no second order diffraction in this case.

Answer

D

Explanation

For a grating, `(e+d)sin theta_n=nlambda`
where `(e+d)=`greating element
`sin theta_n=(nlambda)/((e+d))`
For `n=1, sin theta_1=(lambda)/((e+d))=sin 32^@`
This is more than 0.5. Now `sin theta_2` will be more than `2xx0.5`, which is not possible.