Refraction of Light

Refraction of light

   Light rays travel in straight lines in a homogeneous medium. But whenever a light ray passes from one transparent medium to another, it deviates from its original path at the interface of the two media. In the second medium the ray either bends towards the normal to the interface, or away from the normal. The bending of the light ray from its path in passing from one medium to the other medium is called 'Refraction' of light.

    Let a plane surface separating two transparent media, Medium 1 and Medium 2. Let their refractive indices be n₁ and n₂ respectively. The two media can be any pair such as air and water, or air and glass. Suppose incident ray traveling in medium 1 and  refracted ray traveling in medium 2 shown in figure. Draw a normal . The angle i between the incident ray and the normal is called the angle of incidence. The angle r between the refracted ray and normal is called the angle of refraction.

    The refraction of light takes place according to the following two laws known as  the  laws of refraction :

1. The incidence ray, the refracted ray and the normal to the interface at the incident point all lie in the same plane.

2. The angle of incidence and the angle of refraction satisfy the equation.

                                                   sin i/sin r

This law is called Snell's law and the constant the refractive index of the second medium  with respect to first medium.