Electromagnetic waves form a family called the electromagnetic spectrum. The main groups, in order, are radio waves, microwaves, infrared, visible light, ultraviolet, X-rays and gamma rays. Radio waves have the longest wavelength and lowest frequency. Gamma rays have the shortest wavelength and highest frequency.
Visible light is the small group that our eyes can detect. Its colours, from the red end to the violet end, are red, orange, yellow, green, blue, indigo and violet.
The spectrum is continuous. There are no gaps, and each group merges into the next, so the boundaries between groups are not sharp.
