Two light waves having the same wavelength in vacuum are in phase initially. Then first ray travels a path of length L1 through a medium of refractive index
. The second ray travels a path of length L2 through refractive index
. The two waves are combined to observe interference effect the phase difference between the two when they interfere is:
As we learnt
Optical Path -
- wherein
Distance travelled in vacuum
Distance travelled in a medium of refractive index
Optical path length =
Path difference
Phase difference