Refraction of Light

Q. What is Refraction?
Refraction is the bending of a light when it passes from one medium to another. The bending is caused due to the differences in density and hence difference in speed of light between the two substances.
Hence, we can define
Refraction is the change in the direction of a light passing from one medium to another.
Refraction of light is one of the most commonly observed phenomena, but other waves like sound waves and water waves also experience refraction.
Laws of Refraction of Light

• The incident ray refracted ray, and the normal to the interface of two media at the point of incidence all lie on the same plane.
• The ratio of the sine of the angle of incidence to the sine of the angle of refraction is a constant. This is also known as Snell’s law of refraction.                                                                                   
• Sini/Sinr = µ(Constant called refractive index)

Causes of Refraction
The cause of refraction of light is as follows:

• The frequency of the refracted ray remains constant.
• Due to partial reflection and absorption of light at the interface, the intensity of the refracted ray will be less than the incident ray.
• When the light crosses the boundary between two different media, deviation of light occurs, resulting in refraction such that there is a change in wavelength and speed of light.

Effects of Refraction

• Twinkling of stars is due to refraction of light.
• Mirage and looming are optical illusions which are a result of refraction of light.
• A swimming pool always looks shallower than it really is because the light coming from the bottom of the pool bends at the surface due to refraction of light.

Refraction Examples

• Formation of a rainbow is an example of refraction as the sun rays bend through the raindrops resulting in the rainbow.
• Prism is also an example of refraction.