Young's double-slit experiment is conducted in water `(mu_(1))` as shown in figure and a glass plate of thickness t and refractive index `mu_(2)` is placed in the path of `S_(2)`. Find the magnitude of the optical path difference at 'O'.

Options

A. Optical path difference at `'O'` is `((mu_(2))/(mu_(1))-1)t`.
B. Optical path difference at `'O'` is `(mu_(2)-mu_(1))t`.
C. Optical path difference is independent of position of glass plate, provided light from `S_(2)` passes through it.
D. None of the above

Explanation

Equivalent length of the glass plate in water `=(mu_(2)t)/(mu_(1))`
`:. O.P.D.=((mu_(2))/(mu_(1))-1)t`