# In a young's double slit experiment two films of same thickness 't' but of different refractive indices $\mu_1$ and $\mu_2$ are placed in front of slit A and B respectively. If $( \mu_1 > \mu_2)$ the central maxima will

(a) shift towards A

(b) will shift toward B

(c) will not shift at all

(d) no pattern will be obtained

Optical path difference between the two rays coming from slit A and slit B will be
$(\mu_1 -1)t -(\mu_2-1)t$
$\qquad=\mu_1 t -\mu _2 t$
$\qquad= t( \mu_1-\mu_2)$
If $\mu_1 > \mu_2$
The path difference is $+ve$ .
So the central maxima will shift towards A.
Hence a is the correct answer.