Question

Speed of light in air is 3x10 8 m/s and refractive index is 1.33, find the speed of light in water

Answer 1

Absolute refractive index of water = 4/3

Absolute refractive index of glass = 3/2

Given vg = 2 x 108 m / g

Let velocity in vacuum = v

Refractive index of glass ng = Speed of light in vacuum / Speed of light in glass

ng = v / vg

3/2 = v / (2 x 108 )

v = 3 x 108 m/g

So speed of light in vacuum is 3 x 108 m/g.

Refractive index of water nw = Speed of light in vacuum / Speed of light in water

nw = v / vw

4/3 = (3 x 108 ) / vw

vw = (9/4) x 108 m / s

vw = (2.25) x 108 m / s

So speed of light in water is (2.25) x 108 m / s .

Answer 2

Answer:

2.25 × 10⁸ m / sec

Explanation:

Given :

Refractive index of water = 1.33

Speed of light in air = 3 × 10⁸ m / sec.

We know :

Refractive index = Speed of light in air / Speed of light in water

Speed of light in water = Speed of light in air / Refractive index.

Putting value we get :

Speed of light in water = 3 × 10⁸ m / sec / 1.33 .

Speed of light in water = 2.25 × 10⁸ m / sec

Hence speed of light in water is 2.25 × 10⁸ m / sec