Refractive Index

Speed of light in vacuum= 3.00×10⁸ m/s.

The amount of change in speed of light in a medium depend upon the property of medium(refractive index)
Refractive index is a measure of how much speed of light changes when it enter the medium from air.
Absolute refractive index is the ratio of speed of light in vacuum or air to speed of light in the medium.

       c

n=——

       ν

Relative refractive index

              Speed of light in medium 1

n₂₁ = ————————————–

              Speed of light in medium 2

Refractive index of medium 2 wrt medium 1 is known as refractive index of medium 2.

              Speed of light in medium 2

n₁₂= ————————————–

               Speed of light in medium 1

Refractive index of medium 1 wrt medium 2 is known as refractive index of medium 1.

1)When light goes from rarer medium to denser medium.

 _{Sin i}         n₁

_{——- = —— >1}  

 _{Sin r}         n₂

_{Sin i >Sin r}

∠i > ∠r

Reflected ray bend toward normal.

2)When light goes from denser medium to rarer medium.

Sin i         n₂

——- = ——- <1

sin r         n₁

 Sin i < Sin r

∠i < ∠r

Reflected ray bend away from the normal.

Refractive index depend on nature of material of medium,density of medium,colour or wavelength of light.