Two light rays having the same wavelength lambda in vacuum are in phase initially. Then the first ray travels a path L_(1) through a medium of refractive index n_(1) while the second ray travels a path of length L_(2) through a medium of refractive index n_(2). The two waves are then combined to observe interference. The phase difference between the two waves is :

Two light rays having the same wavelength lambda in vacuum are in phas

1.	Two light rays having the same wavelength lambda in vacuum are in phase initially. Then the first ray travels a path L_(1) through a medium of refractive index n_(1) while the second ray travels a path of length L_(2) through a medium of refractive index n_(2). The two waves are then combined to observe interference. The phase difference between the two waves is :
Answer» `(2PI)/(lambda)(L_(2) - L_(1))` `(2pi)/(lambda)(n_(1)L_(2) - n_(2)L_(1))` `(2pi)/(lambda)(n_(2)L_(1) - n_(1)L_(2))` `(2pi)/(lambda)((L_(1))/(n_(1)) - (L_(2))/(n_(2)))` Solution :For first ray , optical path = `n_(1)L_(1)` Optical path for 2ND ray = `n_(2)L_(2)` path differenc = `n_(1)L_(1) - n_(2)L_(2)` `THEREFORE` phase DIFFERENCE =`(2pi)/(lambda)(n_(1)L_(1) - n_(2)L_(2))`

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