2. Visible light is only a small part of a much larger spectrum containing many other wavelengths which we cannot see. High frequency, short wavelength waves: Gamma rays and X-Rays Ultra-violet, Visible and Infra-Red Low frequency, long wavelength waves: Microwaves, TV waves and radio waves
3. Gamma Rays Gamma rays have a very short wavelength of approximately a million-millionth (10 -12 ) of a metre. Sources of Gamma rays include radioactive substances like uranium. These rays are very dangerous. Gamma rays can be detected using a Geiger-Muller Tube.
4. X-Rays X-rays have a typical wavelength of 10 -10 m. Sources are X-ray tubes and X-rays can be very dangerous if not used carefully. X-rays are detected using photographic film.
5. Ultra-Violet Ultra-violet or UV light has a typical wavelength of 10 -8 m. Sources of UV light are very hot objects (e.g. the Sun) and mercury lamps. UV light causes skin tanning which can be dangerous, leading to skin cancer. UV light also makes fluorescent substances glow. Photographic film can detect UV light.
6. Visible light Visible light has a typical wavelength of 5x10 -7 m. Violet light has the shortest wavelength, red light has the longest wavelength. Visible light is emitted from hot objects, lasers, LEDs and fluorescent substances. We detect visible light with our eyes and photographic film.
7. Infra-Red Infra-red light has a typical wavelength of 10 -5 m. Warm or hot objects emit infra-red. IR can be used to monitor weather, detect people in the dark. Our skin is a detector of IR.
8. Microwaves Microwaves have a wavelength typically of 10 -2 m. They can be dangerous when absorbed by body tissue causing heating. Microwaves are not only used to heat food but also used communicating with satellites and in radar.
9. TV and Radio waves UHF (ultra high frequency) waves are used for TV and mobile phones. VHF (very high frequency) waves are used by local radio and the police. Medium waves can be reflected by the charged ionosphere and the Earth, so they can travel long distances. Earth
