If the light rays pass from one medium to another, at the boundary of two mediums, they shift their path. Refraction is a wave’s bending when it enters a medium at different speeds.

What is the Refraction of Light?

Refraction is a shift in the path of a wave that travels from one medium to another or a gradual change in the medium. Light refraction is one of the most commonly observed phenomena which involves light refraction by a prism. We all understand that in different mediums the speed of light is variable. It happens because of the change in the speed of light from one medium to another.

Refraction of Light

It is called refraction of light when the light rays either bend or change their direction while passing from one medium to the other. When light travels from air to glass, from glass to air, from air to water or from water to air, light refracts.

Laws of refraction states that: the ray of the incident, the refracted ray, and the normal at the point of incidence to the interface of two mediums are all on the same plane.

Important Terms

• The incident ray is considered as an event when the light rays travel from air into glass or liquid.
• The point of incidence is called normal.
• The angle between the incident ray and the normal is the Angle of Incidence.
• The angle between the refracted ray and the normal is the angle of refraction.
• The refraction angle is either smaller or larger than the incidence angle.

Causes of Refraction

The reason for light refraction is as follows

1. the refracted ray amplitude remains constant.
2. The frequency of the refracted ray will be smaller than the incident ray owing to partial reflection and absorption of light at the interface.
3. When the light reaches the border of two different media, light divergence happens due to refraction, resulting in a shift of wavelength and light frequency.

Q.1 What is an optically rarer medium and optically denser medium?

The optically rarer medium is when the speed of light is greater. Whereas, the optically denser medium is when the speed of light is less

For e.g. Glass is a medium that is optically denser than water and air.

As light rays pass from a rarer optical medium to a denser medium, it bends towards the normal. The angle of refraction in this situation is greater than the angle of incidence. It bends as normal as light rays pass from air into glass or air into liquid. This is because, while traveling from air to glass or water, the speed of light rays declines.

As light rays travel from a more optically dense medium towards a more rare medium, it bends away from the normal. In this situation, the refraction rate is greater than the incidence angle. It bends away from the normal as light rays travel from glass to air or from liquid to air.

Q.2. What if the refraction of light takes place twice in case?

For example, when it exits from the air into the glass slab and the other when it enters the air through the glass slab.

As light rays enter the glass slab passing through air it becomes refracted and bend toward the normal. Then, when it falls out of the glass slab the path of the refracted ray shifts again. In this scenario, the rays of the incident and the emerging rays are similar. The perpendicular distance between the incident ray’s original path and the emergent ray from the glass slab is called the lateral displacement of the emergent ray of light and the angle that the emerging ray makes with the normal is called the emergence angle.