Light
Electromagnetic radiation is the term given to a type of radiation which includes, in order of decreasing energy: gamma rays; X-rays; UV rays; visible light (from violet to red); Infra-red; microwaves; radio waves. All EM radiation travels at the speed of light because all it is is different forms of light, only a very small part of which humans can see.
All EM radiation has FREQUENCY and WAVELENGTH. They are inversely proportional to each other, and FREQUENCY x WAVELENGTH = SPEED OF LIGHT.
High frequency radiation is dangerous to living things because individual photons (or "particles of light") carry enough energy to break the chemical bonds which hold DNA together, and this can lead to cancer. This is why X-rays and UV light should be avoided. This is also the reason why in theory microwaves and radio waves cannot cause cancer; the individual parcels of energy are not powerful enough to break bonds. Because electrons in bonds can only accept one photon at a time, the number of photons (aka the intensity of the radiation) is irrelevant; only their strength matters.
First answer by Tigerwhit. Last edit by Theozster. Contributor trust: 92 [recommend contributor]. Question popularity: 58 [recommend question]
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