Alpha radiation is created when 2 protons and 2 neutrons are ejected from a large unstable nucleus. It is identical to a helium nucleus and is a relatively heavy, high energy particle with a charge of +2.
Alpha particles have a velocity in air of 1/20 c. These particles can only penetrate through about 5cm of air and are stopped by paper or layer of skin. Thus making it the least penetrative form of radiation.
The path of the alpha particleis affected by an electric & magnetic field. Alpha particles are highly ionising and therefore harmful to biological material. However it is only a risk if ingested as they are usually absorbed by the thick layer of skin outside.
Beta decay is when electrons are ejected from an unstable nucleus.
– The neutron decomposes into an electron (eejected as beta radiation) and a proton. Hence this type of decay results in atomic number increase.
Beta particles have an electrical charge of -1 and 1/2000 mass of a proton or neutron.
Beta particles are more penetrative than alpha, as they are able to pass through 5m of air and are stopped by a few cm of aluminium.
The path of a beta particle is affected by either an electrical or magnetic field and it isn’t as ionising as alpha radiation.
While beta particles are emitted by atoms that are radioactive, beta particles themselves are not radioactive. It is their energy (velocity) that causes harm to biological material. When transferred, this energy can break chemical bonds and form ions.
It is a very high-energy, ionising radiation. Gamma photons have about 10000 times as much energy as the photons in the visible range of the EM spectrum.
Gamma rays have no mass, no charge, not affected by magnetic or electric fields and cause the least ionisation.
Due to them being pure EM energy, gamma photons travel at the speed of light and can pass through several km of air and up to 15 of lead very dense material. Thus making it the most penetrative of the 3 types of radiation.
Gamma decay itself does not exist. Gamma radiation is emitted in addition to alpha or beta decays.