Question

What is refraction? Define refractive index.

Answer 1

Refraction:

1. Refraction is the bending of a wave when it passes from one medium to another. The bending is caused due to the differences in density between the two substances.
2. A light ray refracts whenever it travels at an angle into a medium of a different refractive index. This change in speed results in a change in direction. As an example, consider air traveling into water. The speed of light decreases as it continues to travel at a different angle.
3. When light travels from air into glass, the light slows down and changes direction slightly. When light travels from a less dense substance to a denser substance, the refracted light bends more towards the normal line. If the light wave approaches the boundary in a perpendicular direction, the light ray doesn’t refract despite the change in speed.
4. An illustrative diagram is shown below.

Refractive index:

1. For a given pair of media and for a given wavelength, when the sine of the angle of incidence is divided by the sine of the angle of refraction, that is, the ratio of the sine of the angle of incidence to the sine of the angle of refraction is known as Snell’s law.

$n=\frac{\sin i}{\sin r}$ where, i is the angle of incidence and r is the angle of refraction and $n$ is the constant known as the refractive index.

2. The refractive index is the ratio of the speed of light in a vacuum to its speed in a specific medium.

3. The term "refractive index" can also refer to the refraction index or index of refraction.

4. The speed of light in a medium is determined by the medium's properties.

5. The speed of electromagnetic waves is determined by the optical density of the medium.