Refraction is the bending of light as it passes from one medium to another, resulting in a change in direction. It is a fundamental concept in physics that describes how light behaves when it encounters a boundary between two different media with different optical properties.

**What is refraction?**

Refraction occurs when light waves travel through a medium with a different refractive index than the medium it is traveling in. The refractive index is a measure of how much a light wave bends as it passes from one medium to another. The angle of incidence (the angle at which light hits the boundary) is equal to the angle of refraction (the angle at which the light waves bend).

**Types of refraction:**

There are several types of refraction, including:

1. **Spherical refraction**: Light travels in a straight line from the point of incidence to the point of refraction, but then changes direction as it passes from one medium to another.
2. **Cylindrical refraction**: Light travels in a curved path from the point of incidence to the point of refraction, and then changes direction as it passes from one medium to another.
3. **Plane-parallel refraction**: Light travels in a straight line from the point of incidence to the point of refraction, and then changes direction as it passes from one medium to another.

**Factors affecting refraction:**

Several factors can affect the refraction of light, including:

1. **Speed of light