Radiation is energy shot out at high speed by atoms. There are two main forms — radioactivity and electromagnetic radiation.
Radiation either travels as waves or as tiny particles called photons.
Radioactivity is when an atom decays (breaks down) and sends out deadly energy such as gamma rays.
Nuclear radiation is the radiation from the radioactivity generated by atom bombs and power stations. In large doses, this can cause radiation sickness and death.
Electromagnetic radiation is electric and magnetic fields that move together in tiny bursts of waves or photons.
There are different kinds of electromagnetic radiation.
The Sun throws out huge quantities of with a different wavelength, radiation of all kinds.
Gamma rays are a very short-wave, atmosphere protects us from the worst, energetic and dangerous form of electromagnetic radiation.
Radio waves are a long-wave, low-energy radiation.
In between these come X-rays, ultraviolet rays, visible light, infrared rays and microwaves.
Together these forms of electromagnetic radiation are called the electromagnetic spectrum. Visible light is the only part of the spectrum we can see with our eyes.
All electromagnetic rays move at the speed of light — 300,000 km per second.
Everything we detect in space is picked up by the radiation it gives out (see astronomy, the Big Bang and radio telescopes).
Radiation is an atom’s way of getting rid of its excess energy.
There are two main kinds of radiation: electromagnetic and particulate.
Electromagnetic radiation is pure energy. It comes from electrons.
Particulate radiation is tiny bits of matter thrown out by the nuclei of atoms.
Particulate radiation comes mainly from radioactive substances such as radium, uranium and other heavy elements as they break down.
Radiation is measured in curies and becquerels (radiation released), rontgens (victim’s exposure), rads and grays (dose absorbed), rems and sieverts (amount of radiation in the body).
Bacteria can stand a radiation dose 10,000 times greater than the dose that would kill a human.
Radiation entering a Geiger counter tube hits the gas atoms there, causing them to ionise. The electrons that are freed by this process spread along the wire, creating electrical pulses, which are counted by a meter.
The Chernobyl nuclear accident released 50 million curies of radiation. A 20 kiloton nuclear bomb releases 10,000 times more radiation.
The natural radioactivity of a brazil nut is about six becquerels (one ten millionth of a curie), which means six atoms break up every second.
The natural background radiation you receive over a year is about 100 times what you receive from a single chest X-ray.