Wave nature of light

Light (or visible light)

Is electromagnetic radiation that can be detected by the human eye. It has a wavelength between 700 nm (red) and 400 nm (violet). It is a form of energy

Infa-red light

Is emitted by warm objects. It can be detected by its heating effect on a blackened thermometer bulb. It effects photographic plates.

Fluorescence

Occurs when a substance absorbs UV radiation and re-emits it as visible light.

Monochromatic light

Is light of one colour only (one wavelength)

Dispersion

Is the splitting up of white light into its constituent colours

Primary colours

Combine to form white light. They are red, green, and blue.

Secondary colours

Are formed when two primary colours are mixed in equal proportions. The secondary colours are magenta, yellow, and cyan

Complementary colours

Are pairs of colours (one primary one secondary) which combine to form white light. Examples are blue with yellow and green with magenta.