Question

In YDSE if a slab whose refractive index can be varied is placed in front of one of the slits. Then, the variation of resultant intensity at mid-point of screen with `mu` will be best represented by `(mu is greater than or equal to 1)

Answer 1

Correct Answer - C
Shift = `((mu-1)tD)/d`
At `mu =1, shift=0`
Therefore, intensity at centre is maximum or `I_0`.
As `mu` increases fringes shift upwards as shown in figure.
So, intensity at P first decreases to zero (as Q
reaches at P), then it further increases to `I_0`(as
point R reaches to P).