In a Young's double slit experiment, films of thickness `t_(A)` and `t_(B)` and refcative indices `mu_(A)` and `mu_(B)` are placed in front of slits A and B respectively. If `mu_(A)t_(A)=mu_(B)t_(B)`, then the central maxima may

Options

A. not shift
B. shift towards A
C. shift towards B
D. none of these

Explanation

The path difference
`Deltax=(mu_(A)-1)t_(A)-(mu_(B)-1)t_(B)`
`rArr Deltax=mu_(A)t_(A)-t_(A)-mu_(B)t_(B)+t_(B)`
`rArr Deltax=t_(B)-t_(A)`
if `t_(B)=t_(A) rArr Deltax=0`
`rArr` no shift
if `t_(B)gt t_(B)` or `t_(B) lt t_(A)`
`Deltax ne=0`
`rArr `central maxima may shift towards A or B