The refractive index of water with respect to vacuum is and refractive index of vacuum with respect to glass is . If the speed the speed of light in glass is 2 × 10⁸ ms^-1, find the speed of light in (i) vacuum, (ii) water.

Given;

Refractive index of (R.I) water w.r.t vacuum;

Refractive index (R.I) of vacuum w.r.t glass ;

Refractive index (R.I) of glass to vacuum will be =

Refractive index of glass to water =

⇒ Refractive index of glass w.r.t water =

⇒

⇒

⇒ speed of light in water

⇒ speed of light in water

Thus, speed of light in water = 2.25 × 10⁸.

Refractive index of water w.r.t vacuum = ^vμ_w ;

⇒

⇒

⇒

Thus, speed of light in vacuum is 3 × 10⁸ m/s.