Physics - Wave Optics Question with Solution | TestHub

The fringe width in an interference pattern is given by $\beta =\frac{\lambda D}{d}$

The angle between the two wave trains (angle subtended by the two coherent sources at the screen) is $\theta =\frac{d}{D}$

From the above two relations, we get:

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

Given:
$\lambda =6\times 10^{-7}$ m
$\beta =0.12$ mm $=0.12\times 10^{-3}$ m

Substituting the values:

$\theta =\frac{6\times 10^{-7}}{0.12\times 10^{-3}}$

$\theta =\frac{6\times 10^{-7}}{1.2\times 10^{-4}}$

$\theta =5\times 10^{-3}$ rad

Answer: $5\times 10^{-3}\mathrm{rad}$