Question

the absolute refractive indices of glass and water are 4\3 and 3\2 respectively. If the speed of light in glass is 2×10^8 m\s ,calculate the speed of light in 1) vaccum,2) water

Answer 1

please note that refractive index for glass is 3/2
and refractive index for water is 4/3
refractive index, n = (speed of light in vaccum/air)/(speed of light in that                                      medium)
⇒n =c/v
⇒c = n×v
so,c = (3/2)×2 ×10^8 m/s 
        = 3×10^8 m/s
∴speed of light in vaccum is 3×10^8 m/s
also,c =n×v = (4/3)×v
⇒3×10^8 = (4/3)×v
⇒v = 2.25×10^8 m/s
∴speed of light in water is 2.25×10^8 m/s