Types of Ionizing Radiation
Alpha Particles
Alpha particles are positively charged and made up of two protons and two neutrons from the atom's nucleus.
Alpha particles come from the decay of the heaviest radioactive elements, such as uranium, radium, and polonium. Even though alpha particles are very energetic, they are so heavy that they use up their energy over short distances and cannot travel very far from the atom.
The health effect from exposure to alpha particles depends significantly on how a person is exposed. Alpha particles lack the energy to penetrate even the outer layer of skin. Hence, exposure to the outside of the body is not a significant concern. Inside the body, however, they can be very harmful. If alpha-emitters are inhaled, swallowed, or get into the body through a cut, the alpha particles can damage sensitive living tissue. The way these large, heavy particles cause damage makes them more dangerous than other types of radiation. The ionizations they cause are very close together - they can release all their energy in a few cells leading to more severe damage to cells and DNA.
Beta Particles
Beta particles are small, fast-moving particles with a negative electrical charge emitted from an atom's nucleus during radioactive decay. These particles are emitted by unstable individual atoms such as hydrogen-3 (tritium), carbon-14, and strontium-90.
Beta particles are more penetrating than alpha particles. Still, they are less damaging to living tissue and DNA because the ionization they produce is more widely spaced. They also travel farther in the air than alpha particles. Still, they can be stopped by a layer of clothing or a thin layer of material, such as aluminum. Some beta particles can penetrate the skin and cause damage, such as skin burns. However, as with alpha-emitters, beta-emitters are most hazardous when they are inhaled or swallowed.
Gamma Rays
Gamma rays are weightless packets of energy called photons. Unlike alpha and beta particles, which have both energy and mass, gamma rays are pure energy. Gamma rays are like visible light but have much more energy. Gamma rays are often emitted along with alpha or beta particles during radioactive decay.
Gamma rays are a radiation hazard for the entire body. They can easily penetrate barriers that can stop alpha and beta particles, such as skin and clothing. Gamma rays have so much penetrating power that several inches of dense material, like lead, or a few feet of concrete, may be required to stop them. Gamma rays can pass entirely through the human body; as they pass through, they can cause ionizations that damage tissue and DNA.
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1-2. What type of radiation is a hazard for the entire body?
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