Question

The refractive indices of glass and water with respect to air are 3/2 and 4/3 respectively. If speed of light in glass is 2 X 10raise to power 8 m/s, find the speed of light in water.

Answer 1

now
speed of light in vacuum is 3x10^8
now
refractive index
=speed of light in vacuum/speed of light in water
therefore
speed of light in water
=3x10^8/4/3
=9x10^8/4
=2.25x10^8

Answer 2

here is your answer

now  

speed of light in vacuum is 3x10^8

now  

refractive index

=speed of light in vacuum/speed of light in water

therefore

speed of light in water  

=3x10^8/4/3

=9x10^8/4

=2.25x10^8