Types of ionising radiation (A level Physics)
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Alpha
An alpha particle is a helium nucleus, with two neutrons and two protons Alpha decay occurs when a nucleus gets too heavy/massive and can no longer support itself. This type of radiation is the least penetrating of the three here, it is stopped in air, by a few mm of paper on by skin. However, alpha is the most ionizing type of radiation, which also makes it the most dangerous if it passes your epidermis by any means. The daughter nucleus of an alpha decay has 2 less protons and 4 less nucleons.
Alpha sources are used in smoke detectors, they induce a charge on a receiving plate so complete a circuit, but when smoke gets in the way the circuit is broken, so the alarm sounds.
Beta
A beta particle is a high-speed electron. Beta decay occurs when a nucleus has too many neutrons to be stable, so one decays into a proton and an electron. The electron is then fired out of the nucleus, but the proton stays in the nucleus. Beta decay is more penetrating than alpha but less than gamma, it is stopped by a few mm of aluminum but not by your skin. Beta decay isn't as ionizing as alpha, but is more than gamma so a beta source is still dangerous. The daughter nucleus of a beta decay has 1 more proton and the same nucleon number.
In beta decay, a quark change occurs-the udd quark structure of the neutron changes to the uud structure of a proton, a down quark changes to an up quark and in the process an electron and an electron anti-neutrino are released.
The anti-neutrino is released to allow for the various energies the electron can be released at, because momentum has to be conserved the anti-neutrino is released. It has 0 charge and rest mass.
Beta sources are used as tracers in medicine and industry, to find tumors in patients and too find cracks in pipes, also to control the thickness of materials.
Positron
This is the opposite of beta decay, where a nucleus gets too few neutrons, so a proton is changed into a neutron and an electron, and a neutrino. It has the same characteristics of beta decay, but every particle is changed for it's anti-particle.
Gamma
Gamma radiation is a type of electromagnetic wave, with a high frequency and a short wavelength, the photon energy is very high. This radiation is released when a nucleus has too much energy, and settles it to a more stable state, however it doesn't change the structure of the atom at all. Other radioactive decays are often accompanied by a gamma ray released. This is the most penetrating and least ionizing radiation. It partially stopped by meters of concrete or cm's of lead but is never fully absorbed, however it does the least damage of all the three.
Gamma radiation is used in industrial tracers, to track pipes underground.
Ionization
These are examples of ionizing radiation, which can be harmful to organisms. They ionize the atoms of an organism, so creating free-radicals which can cause cancer.
