A ray of light is incident on a glass-water interface at an angle i, it merges finally parallel to the surface of the water as shown in the figure, the value of μg would be:
1 /sin i
By applying snell's law
At first surface: (glass to water)
sinisinr=absolute refractive index of waterabsolute refractive index of glass=μωμg=43μg ....(1)
A second surface: (water to air)
sinisinr=absolute refractive index of airabsolute refractive index of water
sinr=1μω=34 ....(2)
substituting this value in (1)
4sini3=43μg
⇒μg=1sini