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Radiation consists of three types of particles:
1. Alpha particles:
An alpha particle consists of 2 protons and 2 neutrons. So it has a mass of 4 units. It shoots out of the radioisotope at high speed but slows down quickly in air. It can't pass through paper or skin.
The radioisotope americium-241 is used in smoke alarms. It has 95 protons, and decays by giving out an alpha particle. That leaves 93 protons, which means it has turned into neptunium:
241Am 237Np + an alpha particle
95 93
The mass number has changed into 237.
2. Beta particles:
A beta particle is a fast electron. This means that a beta particle has no mass. It can travel 20 or 30 cm in the air, and also through skin, paper and thin sheets of metal.
It is formed when an neutron turns into a proton and an electron. The new electron is thrown out. So the mass of the isotope doesn't change but its protons increase by one.
A carbon-14 atom has 6 protons. It decays by giving off a beta particle. Now it has 7 protons. It has turned into a nitrogen atom:
14C 14N + a beta particle
6 7
3. Gamma rays:
Gamma rays are usually given out at the same time as alpha and beta particles. They are high-energy rays, like X-rays. They travel at the speed of light. They can travel several metres in the air, and through thick sheets of metal. They can also travel deep into your body. So they are very dangerous, but thick sheets of lead or thick concrete will stop them.
Questions:
1. Name the three types of radiation and say what they are.
2. Explain why the waste of nuclear power-stations is always
carried deep below ground.
3. Why are the gamma rays so dangerous for the humans?
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