Question

If the absolute refractive index of glass and water is 3/2 and 4/3
respectively then find the ratio of speed of light in water and glass.
​

Answer 1

3/2 : 4/3

=> 4/2

=> 2

Hence, the ratio of speed of light in water and glass is 2.

Answer 2

Explanation:

Given : n

water

=

3

4

n

glass

=

2

3

v

glass

=2×10

8

m/s n

air

=1

Speed of light in a medium v

medium

=

n

c

where c and n are the speed of light in vacuum and refractive index of medium respectively.

(a) : v

glass

=

n

glass

c

∴ 2×10

8

=

(3/2)

c

⟹c=3×10

8

m/s

(b) : v

water

=

n

water

c

∴ v

water

=

(4/3)

3×10

8

=2.26×10 raise to 8

m/s