1. find the speed of light in diamond if its refractive index is 2.5 (speed of light in vaccum = 3 * 10⁸msec).
2. find the refractive index of glass if light travels in it with speed of 2*10⁸msec ( speed of light in vaccum= 3*10⁸msec).
3. if the speed of light in water of refractive index 43 is 2.25*10⁸ms, what will be the speed of light in vaccum?
4. if the speed of light in glass is 2*10⁸ms, what will be the speed of light in water? (refractive index of glass with respect to water is9/8).

• answers-----

1. 1.2*10⁸
2. 1.5
3. 3*10⁸
4. 2.25*10⁸

Refractive index of a material = speed of light in vaccum / speed of light in that medium

a) speed of light in diamond = speed of light in that medium /Refractive index of diamond = 3*10⁸/2.5 = 

 = 1.2*10⁸m/sec

b) refractive index of glass = 3* 10 ⁸ / 2*10⁸ = 1.5

c) speed of light in vaccum =   4.3 *2.25*10⁸ = 9.675 * 10⁸ m/sec

d) refractive index of water * speed of  light in water = refractive index of glass * speed of light in glass

speed of  light in water = refractive index of glass with respect to water * speed of light in glass

= (9/8)*2*10⁸=2.25 *10⁸ m/sec