Question

Light is incident at an angle $\phi$ with the normal to a plane containing two slits of separation $d$. Select the expression that correctly describes the positions of the interference maxima in terms of the incoming angle $\phi$ and outgoing angle

• A. $\sin \phi+\sin \theta=\left(m+\frac{1}{2}\right) \frac{\lambda}{d}$
• B. $d \sin \theta=m \lambda$
• C. $\sin \phi-\sin \theta=(m+1) \frac{\lambda}{d}$
• D. $\sin \phi+\sin \theta=m \frac{\lambda}{d}$

Answer 1

Answer: (D)

Path difference $=d \sin \phi+d \sin \theta$
For maxima, $\Delta x=m \lambda$
$\Rightarrow \sin \phi+\sin \theta=\frac{m \lambda}{d}$