Rev. Notes > IGCSE > Light Previous Topic Light Next Topic Topics
 Nature of light Important features of light Reflection of light Use of mirror (Periscope) Refraction of light Refractive index Critical angle Total internal reflection Use of prism (Periscope) Fiber-optics Convex lens Behavior of standard rays after passing through convex lens Image formed by convex lens Nature and position of image produced by convex lens Principle of camera Dispersion of light Newton's experiment for dispersion of light Improvement in Newton's experiment for dispersion of light Recombination of colors Rainbow Reflection through plane mirror Image through plane mirror Test Yourself

## Refractive index

The refractive index of a material indicates how strongly the material changes the direction of the light. It is calculated using the formula

Refractive index = Sin i / Sin r

where

i = angle of incidence

r = angle of refraction

 Material Refractive index Vacuum 1 Air 1.0 Water 1.3 Glass 1.5 Sapphire 1.75 Diamond 2.4

The refractive index can also be determined by using the following relation

Refractive index = 1 / Sin C

where C is the critical angle.

We can also use the following equation to determine the refractive index

Refractive index = c / v

where

c = speed of light in vacuum

v = Speed of light in the material

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