Question

In a YDSE with identical slits, the intensity of the central bright fringe is $I_0$.If one of the slits is covered, the intensity at the same point is

• A. $2I_0$
• B. $I_0$
• C. $I_0/2$
• D. $I_0/4$

Answer 1

The correct option is D $I_0/4$

Let intensity due to each slit on the central bright fringe be $I_1$.

Thus intensity at the point of bright fringe due to interference of the light from two slits is $I_0=I_1+I_1+2\sqrt{I_1.I_1}\cos \varphi$

For central bright fringe, $\varphi =0$

$⟹I_0=4I_1$

$⟹I_1=\frac{I_0}{4}$