1. Key ideas  The electromagnetic spectrum is made up of radio waves, microwaves, infrared radiation, visible light, ultraviolet radiation, X-rays and gamma rays. They have different wavelength ranges. 12.3 Waves of the electromagnetic spectrum

2. Electromagnetic wave Typical wavelength SourceDetectorApplication Radio waves Microwaves Infrared radiation radio communication, radio and TV broadcasting 10 –1 m – 10 4 m radio and TV transmitter antenna 10 –2 m microwave transmitter microwave receiver microwave oven, satellite communication, radar 10 –4 m Warm or hot objects, the Sun skin, phototransistor, blackened thermometer thermography, infrared viewer, infrared lamp, remote control, auto-focus camera

3. Electromagnetic wave Typical wavelength SourceDetectorApplication Visible light Ultraviolet radiation X-rays 10 –10 m 10 –8 m 10 –7 m hot objects, the Sun, fluorescent materials very hot objects, the Sun, mercury lamp X-ray tube human eyes, photographic film fluorescent materials photographic film illumination production of vitamin D, sterilization, checking banknotes medical diagnosis, checking for cracks in joints

4. Electromagnetic wave Typical wavelength SourceDetectorApplication Gamma rays10 –12 m radioactive substances photographic film, Geiger- Muller counter kill cancer cells, sterilize food