Summary
Highlights
Alpha radiation is used in smoke alarms, where its blockage by smoke triggers an alarm. Beta radiation is utilized for measuring the thickness of materials like paper, by detecting changes in absorption. Gamma radiation is employed in medical imaging, where an injected gamma-emitting source allows for the formation of 3D images of the patient's internal organs.
Alpha particles are made of two neutrons and two protons, essentially a helium nucleus. They are emitted when a nucleus is too large, causing the unstable nucleus to decay and become smaller. Alpha radiation is highly ionizing, producing 30,000 to 50,000 ions per centimeter of air, but it has the shortest range, from 1 to 5 centimeters in air, and cannot penetrate skin.
Beta particles are fast electrons with very small mass and a negative charge. They are emitted when a nucleus has too many neutrons, converting one into a proton. Beta radiation is less ionizing than alpha, creating 50 to 100 ions per centimeter of air, but it has a longer range than alpha, about 1 meter in air, up to 2 centimeters in living tissue, or 3 millimeters in aluminum.
Gamma particles are the highest energy electromagnetic waves or photons, possessing no mass or charge. They are released when a nucleus has excess energy. Gamma radiation is the least ionizing, generating only three to five ions per centimeter of air, but it has the longest range, spanning hundreds of kilometers in air and tens of centimeters through living tissue. Its intensity is halved by approximately 1.2 centimeters of lead.
The dangers of radiation come in two forms: irradiation, which occurs when a radioactive source is outside the body, and contamination, which happens when the source is inside the body. Alpha radiation poses little irradiation danger because it cannot penetrate skin, but severe contamination danger due to its high localized damage. Beta radiation presents moderate irradiation danger as it can penetrate skin but usually not internal organs, and a moderate contamination danger if ingested. Gamma radiation causes a high irradiation danger due to its deep penetration into organs, but the lowest contamination risk because most gamma rays pass out of the body.