The electromagnetic spectrum is a family of waves, and each region is useful for a different job because the waves behave differently. In order of increasing frequency the regions are radio, microwave, infrared, visible light, ultraviolet, X-ray and gamma ray.
Radio waves are used for broadcasting, carrying television and radio programmes. Microwaves are used for satellite communications and mobile phone signals, and also in microwave ovens, where the water in food absorbs them and heats up. Infrared is used in remote controls, electric heaters, grills and toasters, and in thermal imaging cameras that detect the heat objects give out.
Visible light is used in photography and in optical fibres, which carry signals as pulses of light. Ultraviolet is used in sun tanning beds, in fluorescent lamps and to reveal security marks on bank notes. X-rays are used to take medical images of bones and in airport security scanners. Gamma rays are used to sterilise medical equipment and food, and to treat cancer by killing cancer cells.