Question

Two points sources separated by $2.0m$ are radiating in phase with $\lambda =0.50m$. A detector moves in a circular path around the two sources in a plane containing them. How many maxima are detected?

• A. $16$
• B. $20$
• C. $24$
• D. $32$

Answer 1

The correct option is A $16$

For maxima $d\sin \theta =n\lambda$

On circle, for $-\frac{\pi }{2}\le \theta \le \frac{\pi }{2}\Rightarrow n=\frac{2d}{\lambda }+1$

for $\frac{\pi }{2}<\theta <-\frac{\pi }{2}\Rightarrow n=\frac{2d}{\lambda }-1$

Total number of maxima $n=\frac{4d}{\lambda }=\frac{4\left(2\right)}{0.5}=16$