Question

Two plane monochromatic coherent waves produce interference pattern (of alternately bright and dark bands) on a screen. When the angle $\theta$ between the two beams is decreased the fringe width

• A. increases
• B. increases and then decreases
• C. is unaffected
• D. decreases

Answer 1

The correct option is A increases

We know that,
Fringe width is given by

$\beta =\frac{\lambda }{\theta }$

when $\theta$ is decreased, $\beta$ increases.

Hence, option $\left(A\right)$ is correct.