Problem

In YDSE, having slits of equal width, let

\beta

be the fringe width and

I_0

be the maximum intensity. At a distance

x

from the central bright fringe, the intensity will be (1)

I_0 \cos\left(\frac{x}{\beta}\right)

(2)

I_0 \cos^2 \frac{2\pi x}{\beta}

(3)

I_0 \cos^2 \frac{\pi x}{\beta}

(4)

\frac{I_0}{4} \cos^2 \frac{\pi x}{\beta}