# Positron: Definition, Symbol & Production

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• 0:01 Positron Definition
• 1:45 Production & Uses
• 2:59 Lesson Summary
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Lesson Transcript
Instructor: Richard Cardenas

Richard Cardenas has taught Physics for 15 years. He has a Ph.D. in Physics with a focus on Biological Physics.

In this lesson, you will learn about anti-matter and the positron. You will learn how positrons are produced, the symbol for a positron, and some common uses.

## Positron Definition

Opposites are a common feature in physics. For example, there are positive charges and negative charges; there is a magnetic North Pole to oppose the magnetic South Pole; and there is matter and antimatter. Antimatter is the opposite of matter. It may look like matter, and it may even feel like matter, but it will have at least one property different from matter, like a different charge, for example. Also, when matter meets antimatter, they annihilate each other in a flash of light.

A positron is the antimatter counterpart of an electron (also called anti-electron). This table compares the properties of the electron and positron.

Property Electron Positron
Mass 9.109 E-31 kg 9.109 E-31 kg
Spin 1/2 1/2
Charge -e +e

The mass of the electron and positron are the same. The spin, a type of angular momentum carried by the electron and positron, is the same for both. However, the electron and positron have the opposite charge. The electron has a negative charge, and the positron has positive charge. Note that e is the symbol for the fundamental charge of an electron and a proton, which has a value of e = 1.602 * 10^-19C

For comparison, the symbols used to represent electrons and positrons are shown on the screen.

Positrons were theoretically predicted by P.A.M Dirac in 1928, when he argued that the equation he came up with (now called the Dirac equation), does not rule out the possibility that there are electron-like particles with positive charges and negative energies. In 1932, Carl David Anderson discovered positrons in a cloud chamber image used to look at cosmic radiation. Positrons are stable in a vacuum, but when not in a vacuum, positrons quickly interact with electrons and annihilate each other to produce gamma radiation.

## Production and Uses of Positrons

One way to create positrons is in a process called pair production. In pair production, a high-energy photon (usually a gamma ray) interacts with a heavy nucleus, creating a matter-antimatter pair, such as an electron and a positron.

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