Alpha ray

Alpha Ray

An alpha ray or alpha radiation is a type of ionizing radiation consisting of two protons and two neutrons bound together into a particle identical to a helium-4 nucleus. It is generally produced in the process of alpha decay, but may also be produced in other ways. Alpha particles are named after the first letter in the Greek alphabet, alpha (α). They have a positive charge +2e, but as a nuclear equation describes they have no charge.

History

Alpha rays were discovered by Ernest Rutherford in 1899. He named them alpha rays based on their ability to penetrate matter; alpha rays are less penetrating than beta rays and gamma rays. Rutherford also noted that alpha rays do not penetrate a sheet of paper or the outer layer of human skin.

Properties

Alpha particles have a charge of +2e and a mass of 4 atomic mass units (amu). They are a highly ionizing form of particle radiation, and when resulting from radioactive alpha decay, they have low penetration depth. They can be stopped by a few centimeters of air, or by the skin.

Health Effects

Despite their low penetration depth, alpha particles are potentially hazardous when ingested or inhaled, as they can cause ionization damage to living cells. The health effects of alpha particles depend largely on how they are taken into the body and the types and amounts of radiation involved.

Detection and Protection

Alpha particles can be detected with a Geiger-Mueller counter, a common type of particle detector. Protection from alpha particles can be as simple as a sheet of paper or clothing, as alpha particles are not able to penetrate the outer layer of skin. However, if alpha particles are ingested or inhaled, they can be harmful, so precautions should be taken to avoid this.

See Also

• Beta Ray
• Gamma Ray
• Ionizing Radiation
• Radioactive Decay

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