Relative refractive index– It is the ratio of speed of light in one medium to the speed of light in another medium • Absolute refractive index– It is the ratio of light in vacuum to the speed of light in another medium.

One of the best examples of this is when a pencil is put in a half-filled glass of water. Notice how the pencil above the water looks normal, but under the water, it looks bent and slightly larger. This is because of refraction.

Refraction is the change in direction of a wave at such a boundary. It is important to be able to draw ray diagrams to show the refraction of a wave at a boundary. A ray diagram showing refraction at the boundary between air and glass.

According to Snell’s law, the angle of refraction, θr, depends on the angle of incidence, θi, and the ratio of the refractive indices of the two media that make up the interface. If the media have identical refractive indices, there is no refraction and the angle θr=θi.

A line or a spot of ink on a paper always appears to be raised when viewed through the glass slab due to the refraction of light. Twinkling of stars is due to the refraction of light. Optical illusions such as mirage and looming are also produced due to refraction of light.

If the refractive indices are same in both medias then there will be no refraction and light will pass without any refraction. And when the incident ray is striking perpendicular to one media to another the light will pass without any refraction.

This is one of the ways to think about refraction: it occurs to conserve the in-plane wave vector. When light is at normal incidence, the in-plane wave vector is zero, so there’s no need for refraction.

90 degrees

So, the angle of inciden is zero and hence the angle of refraction is also zero. In other words,the ray which is incident normally on the interface between the two different media, propagates un deviated from one medium to other and there is no refraction.

For refraction to occur substances must be transparent and light ray must pass from region of one index of refraction to another i.e. both substances should have different refractive indices should and the light ray must impinge at an angle other than normal which must not be less than the critical angle.

The normal is a line perpendicular (forming a 90 degree angle) to the boundary between the two substances. The bending occurs because light travels more slowly in a denser medium. Since the light is passing from air (less dense) into water (more dense), it is bent towards the normal.

Reflection is the bouncing back of light when it strikes a smooth surface. Refraction is the bending of light rays when it travels from one medium to another.

Refraction in a water surface Refraction occurs when light goes through a water surface since water has a refractive index of 1.33 and air has a refractive index of about 1. This is due to the bending of light rays as they move from the water to the air.

Refraction of light is the phenomenon of change in the path of light in going from one medium to another. • In going from a rarer to a denser medium, the ray of light bends towards normal and in going from a denser to a rarer medium, the ray of light bends away from normal.