1.12 - Refraction
What refraction is
- Refraction is when a wave changes direction as it crosses a boundary between two materials at an angle.
- The normal is an imaginary line drawn at right angles to the boundary, at the point where the wave meets it.
- A wave bends only if it hits the boundary at an angle to the normal.
- A wave travelling along the normal carries on in the same direction without bending, although its speed and wavelength still change.
Which way the wave bends
- A wave that slows down as it crosses a boundary bends towards the normal.
- A wave that speeds up as it crosses a boundary bends away from the normal.
For example, light passing from air into glass slows down and bends towards the normal. Passing back out into air, it speeds up and bends away from the normal.
TermDefinition
RefractionThe change in direction of a wave as it passes from one material into another at an angle, because its speed changes.
NormalA line drawn at right angles to a surface or boundary at the point where a ray or wave meets it. A force or pressure that acts at right angles to a surface is also said to act normal to it.