Core facts
- Electromagnetic radiation is best understood as wave of energy,produced by oscillating electric and magnetic fields
- Physicists divide this energy into a spectrum of named bands, according to frequency and wavelength. In this spectrum, our senses detect only heat (infrared) and visible light.
- In a vacuum, all electromagnetic wave travel at a speed of roughly 300,000km per second -the speed of light.
- Electromagnetic waves can also travel through matter, at speed reduced by up to a half
Up to 3000MHz use in radio and television broadcasting, telecommunications networks, cordless telephones, wireless computer networks, radio telescopes.
The usable spectrum of radio frequencies is devided into bands and regulated nationally and internationally to avoid interference between broadcasters.
2.Microwaves
3000MHz to 300GHz use in telecommunications networks, microwave ovens, mobile telephones, radar, microwave telescopes
Absorbed by water molecules in food to cook it in a microwave oven, but not absorbed by plastics or ceramics.
3.Infrared
300GHz to 400 THz Use in electric heaters, cookers, toasters, remote controls for VCRs, aerial surveying, night vision equipment, thermal-imaging cameras, infrared astronomy.
Prodused by warm or hot objects, and generally indentifiable as heat, detected by the eyes of some animals couses warming when absorbed
4.Visible light
400 to 700THz used in photography, cinematography, tv, power generation (by photocell). The range of radiation detected by human eyes, power photosynthesis in plants.
Splits into the colours of the rainbow, red ,orange, yellow, green, blue, indigo and violet.
5.Ultraviolet
700THz to 300PHz use in some night vision equipment,hospitals (for sterilisation of equipment), optical brighteners in washing powder.
Couses suntan and sunburn in humans, and some cancers can be detected by insect eyes, intense ultraviolet rays from the sun are absorbed by the ozone layer in the Earth's atmosphere.
6. X-rays
300 PHz to 30 EHz used in X-ray equipment (for observing dense internal body structures,like bones), checking joints and welds in metal, destroying cancer cells.
X-ray pass through many solids, including human soft tissue, can cause genetic mutation and cancers, can damage some electronic equipment.
7.Gamma rays
More than 30 EHz used in checking dense structures in engineering, destroying cancer cells.