Consider the arra

Let the intensity of slits and be . For and , The distance from the central maximum is .

So the path difference is

Given,

And the corresponding phase difference is

Now, intensity at each slit is given by

Here, P is also central maxima. So the intensity is

(a)For ,

and

Therefore, intensity at each slit is

.

This means that both slits and would be dark. Thus intensity at P would be zero.

(b)For ,

and

Therefore, intensity at each slit is

.

Hence intensity at P is

(c)For ,

and

Therefore, intensity at each slit is

.

Hence intensity at P is