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Anti-matter

For every type of particle there is a corresponding anti-particle which has exactly the same rest mass as the particle but opposite charge.The antiparticle of the electron is the positron.Positron emitters are mostly made artificially, although a few natural isotopes (such as potassium-40) emit positrons.Positron emission takes place when a proton changes into a neutron in an unstable nucleus with too many protons. Some of the nuclei in the substance absorb the extra protons and become unstable positron emitters.

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Specification: AQA Physics (7407), AS-level, 3.2.1.3 Particles, antiparticles and photons. Topic: Particles and Radiation.

Key terms in this lesson

Lepton
A fundamental particle that does not interact through the strong interaction, for example the electron, the muon and their associated neutrinos.
Hadron
A particle made up of quarks that interacts through the strong interaction; hadrons are divided into baryons and mesons.
Muon
A negatively charged lepton, similar to but much heavier than the electron, produced for example by cosmic rays in the atmosphere.
Neutrino
An uncharged, almost massless lepton that interacts only very weakly with matter and is emitted, along with a beta particle, in beta decay.

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