Speed of light will be minimum in which of the following mediums?

Option 4 : Diamond

The correct answer is Diamond.

• Speed of light is inversely proportional to refractive index. 
• The ratio of the speed of light in a vacuum to the speed of light in a medium is called the refractive index of that medium.
• It is also called as absolute refractive index.
• The vacuum has a refractive index of 1.
• The refractive index of water is 1.333. 
• The refractive index of kerosene is 1.44.
• The refractive index of flint glass is 1.65.
• The refractive index of diamond is 2.42.
  • Hence Speed of light is minimum in Diamond.
• The change in the speed of light when it passes through a diamond is 
  • ⇒ Δs  = (1.24 - 3) × 108 = -1.76 × 108 m/s
• The speed of light when passing through a diamond decreases by 59%.