Two light waves having the same wavelength `lambda` in vacuum are in phase initially. Then the first ray travels a path of length `L_(1)` through a medium of refractive index `mu_(1)`. Then second ray travels a path of length `L_(2)` throug a medium of refractive index `mu_(2)`. The two waves are then combined to observed interference effects. The phase difference between the two, when they interfere, is

Options

A. `(2 pi)/(lambda) (L_(1) - L_(2))`
B. `(2 pi)/(lambda) (mu_(1) L_(1) - mu_(2) L_(2))`
C. `(2 pi)/(lambda) (mu_(2) L_(1) - mu_(1) L_(2))`
D. `(2 pi)/(lambda) [L_(1)/(mu_(1)) - (l_(2))/(mu_(2))]`

Answer

b

Explanation

Effective path difference is `mu_(1) L_(1) - mu_(2) L_(2)`.