Refraction of Light
When the light is from one medium to medium with different optical densities, the path of light gets bent or deviated from the original path. This phenomenon is called the Refraction of Light.
Causes of Refraction of Light
Light rays get deviated from the original path when entering into another medium with different optical densities.
This deviation is due to a change of speed of light when entering into another medium.
This is because every medium has its unique optical density that affects the speed of light.
The velocity of light in low optical density or rarer medium is higher than the high optical density or denser medium.
Refraction of Light from a plane transparent Surface
When the light goes from an optically rarer medium to a denser medium, it curves toward the normal.
When the light goes from a denser to the rarer medium it turns away from the normal.
A light incident normally on a denser medium goes without any divergence.
The Laws of Refraction of Light
The incident ray, the refracted ray, and the normal, all lie in the same plane.
“The ratio of the sine of the angle of incidence to the sine of the angle of refraction is a constant for a light of a given colour and for the given pair of media and this law is also called Snell’s law of refraction.” (Tamil Nadu Samacheer Kalvi #)
If i is the angle of incidence and r is the angle of refraction, then
Sin i / sin r = Constant.
This constant is called the refractive index of the second medium with respect to the first medium.
It is represented by ?.
Note that the refractive index has no unit; it is the ratio of two similar quantities.