Question

Find The Speed Of Light In Diamond If It's Refractive Index is 2.5

Answer 1

Speed of light in vacuum=3×10⁸m/sec
Given refractive index of Diamond(n)=2.5
Let the speed of light in Diamond be'x'm/sec.
We have, 
Refractive index=Speed of light in vacuum/Speed of light in medium
⇒2.5=3×10⁸/x
⇒x=3×10⁸/2.5
⇒x=1.2×10⁸ m/sec
Therefore, the speed of light in Diamond=1.2×10⁸m/sec.

Answer 2

Given, Refractive index of diamond = 2.5

Speed of light in vaccum = 3× 10^8 m/s

Refractive index = Speed of the light in vaccum / Speed of the light in the medium

Speed of the light in medium = Speed of the light in vaccum / Refractive index

= 3×10^8 / 2.5

= 1.2×10^8 m/s.

Therefore the speed of light in daimond is 1.2×10^8 m/s.

:)