Question

In Young's double -slit experiment, the intensity of light at a point on the screen, where the path difference is $\lambda$ , is I. The intensity of light at a point where the path difference becomes $\frac{\lambda }{3}$ is

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

Answer 1

The correct option is A $\frac{I}{4}$

$I=4I_{0}co{s}^2\frac{\varphi }{2}$; when $\varphi =\frac{2\pi }{\lambda }x$
when $x=\lambda ;\varphi =2\pi ;I=4I_0$
when $x_1=\frac{\lambda }{3};\varphi =\frac{2\pi }{3};I_1=I_0$
$\frac{I_1}{I}=\frac{I_0}{I_1};I_1=\frac{I}{4}$