Refraction

Basics of Refraction

Refraction is the bending of waves when they move from one medium into another medium of a different density.
The change in direction is due to the change in speed of the waves.
Light, sound, and water waves can all experience refraction.
The medium refers to the substance or material that the wave is travelling through, which could be air, glass, water etc.

Laws of Refraction

There are two laws of refraction: the first law states that the incident ray, the refracted ray and the normal to the interface of two transparent medium at the point of incidence all lie in the same plane.
The second law, also known as Snell’s law states that the ratio of sine of the angle of incidence to the sine of the angle of refraction is a constant, for the light of a given colour and for the given pair of media.
This constant value is known as the refractive index.

Angle of Incidence and Angle of Refraction

The angle of incidence is the angle between the incident ray and the normal at the point of incidence in the first medium.
The angle of refraction is the angle between the refracted ray and the normal at the point of incidence in the second medium.
When light travels from a denser to a less dense medium, it gets refracted away from the normal and vice versa.

Total Internal Reflection

When the angle of incidence is greater than the critical angle, total internal reflection occurs. This phenomenon is utilised in fibres of fibre optic cables.

Refraction in Everyday Life

Lenses in cameras and our eyes work on the principle of refraction to focus light.
Rainbows are a natural phenomenon caused by refraction, reflection and dispersion of sunlight by water droplets in the atmosphere.
Prisms split white light into different colours by refracting the colours at different angles.
Mirages are optical illusions caused by the refraction of light in the Earth’s atmosphere.

Understanding and making calculations based on refraction will help in explaining various natural phenomena. Additionally, many modern technologies are based on refraction such as optical fibres and lenses. It forms a vital part of wave theory in physics.