Q. Light is incident normally on a diffraction grating through which the first order diffraction is seen at $32{^\circ}$. The second order diffraction will be seen at
A) $48{^\circ}$
B) $64{^\circ}$
C) $80{^\circ}$
D) There is no second order diffraction in this case
Explanation
(d) For a grating $(e + d)\sin{\theta_{n} = n\lambda}$
Where $(e + d) =$ grating element
$\sin\theta_{n} = \frac{n\lambda}{(e + d)}$
For $n = 1,\sin\theta_{1} = \frac{\lambda}{(e + d)} = \sin{32{^\circ}}$
This is more than 0.5. Now $\sin\theta_{2}$ will be more than $2 \times 0.5$, which is not possible
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.