Question

In the Young’s double slit experiment the resultant intensity at a point on the screen is 75% of the maximum intensity of the bright fringe. Then the phase difference between the two interfering rays at that point is

• A. $\frac{\pi }{6}$
• B. $\frac{\pi }{4}$
• C. $\frac{\pi }{3}$
• D. $\frac{\pi }{2}$

Answer 1

The correct option is C $\frac{\pi }{3}$

$I=4I_{0}co{s}^2\frac{\varphi }{2}$
$\frac{75}{100}{I}_{max}=I_{max}co{s}^2\frac{\varphi }{2}$
$\frac{\sqrt{3}}{2}=cos\frac{\varphi }{2}$
$\frac{\varphi }{2}={30}^{\circ };\varphi ={60}^{\circ }=\frac{\pi }{3}$