What is absolute refractive index??

Refractive index (n) is a dimensionless quantity that has no units. Since both numerator and denominator are in meters per seconds (m/s), both units cancel each other. This makes refractive index simply a number. 

This type of refraction is the bending of light rays when they pass through the atmosphere of Earth because of the change in the air density. The density of air varies with pressure and temperature. 

Due to the atmospheric refraction, celestial objects appear higher than they actually are. This

The refractive index is an optical property of the material that describes how much does the light bend or refract while passing from one medium to another. It is the ratio of spee of light in vacuum (c) to speed of light in a material (v)$n=\frac{c}{v}$ Refractive index is the reason which causes refraction. When

μ? sin 30° = μ? sin θ

⇒ 2.42 × (1/2) = (1) sinθ
sinθ = 1.21 > 1
Refraction is not possible, total internal reflection