Refraction

Refraction

Refraction is the process by which a ray of light changes speed (refracts) when passing between two different mediums (materials). 

The following video shows a brief introduction to Refraction.

How to label Optics diagrams

The following diagram shows how to label all optics diagrams.

The most important line to draw on these diagrams in the Normal, a line drawn at right angles to the surface, which all angles are measured from. 

If we look closely at the transition from air to glass, we can see that the angle of incidence is greater than the angle of refraction. 

This is because:-

1. When the wave enters the more dense medium it slows down and refracts towards the normal. 

2. When the wave enters the less dense medium it speeds up and  it refracts away from the normal.

Rectangular Block

The above diagram shows how the path of light is refracted by the rectangular block.

The diagram shows:-

1. Angle b is equal to angle c (They form a geometrical "Z angle")

2. Angle a is equal to angle d (as long as only two media are involved)

Semi-circular Block

In the rectangular block, refraction occurs twice, but in a semi-circular block refraction occurs only once. This is because the light entering the curved side of the block enters along the normal, so no refraction occurs. Refraction only occurs at the plane glass boundary. 

Triangular Prism

When a ray of white light passes  through a triangular prism, the ray is refracted twice. The overall effect of these refractions is to cause the white light to be dispersed. This causes a spectrum to be observed.