Alpha particles, beta particles, and gamma rays are the three most frequent forms of radiation. Radiation comes in all sizes, from huge atoms to tiny electrons; it can be visible light that results when an atom is knocked off its center of gravity by a cosmic ray or a particle beam from a particle accelerator; or it can be absorbed by tissues to cause cancer. The four basic types of radiation are: alpha, beta, gamma, and neutron.
Alpha particles are helium nuclei. They are the most common form of radiation found on earth, and they account for about 95% of all radioactive material. Beta particles are electrically charged subatomic particles. They are the second most common form of radiation, making up about 5% of all radioactive material. Gamma rays are electromagnetic waves with a frequency greater than any sound wave but less than that of ultraviolet light. They are the third most common form of radiation, accounting for just under 1% of all radioactive material. Neutrons are neutral particles like electrons but with a mass comparable to that of a proton. They are the fourth most common form of radiation, making up only 0.000000001% of all radioactive material.
Radiation is classified into four types: alpha, beta, neutrons, and electromagnetic waves such as gamma rays. Radioactive elements can be used in medicine to create images of organs inside the body (using radiography) or to treat cancer by killing tumor cells with radiation therapy or radiology. Certain elements also have radioactive isotopes that can be used as probes to study the structure and function of molecules and cells.
Alpha particles are helium atoms. They are the most energetic form of ionizing radiation and the only type capable of penetrating human skin. Alpha radiation comes from the decay of radioactive isotopes such as helium-4, carbon-12, nitrogen-14, oxygen-16, and iron-56. It is a risk factor for cancer because it can pass through bone without damaging it. Living tissue is more likely than rock to absorb an alpha particle, so the skin is the part of the body most at risk from this type of radiation. The chance of being affected increases with age because muscles, bones, and skin are all susceptible to alpha radiation. People who handle radioactive materials regularly face a higher risk of developing cancer later in life.
Beta particles are electrons. They are less abundant than alpha particles but have a greater impact because they are more reactive.
There are three types of radiation that radioactive particles can release. They are referred to as alpha, beta, and gamma. The nucleus of the atom emits all three forms of radiation. Alpha particles are helium nuclei and account for about 1 in 5 billion decays. Beta particles are electrons and account for about 99 percent of decays. Gamma rays are electromagnetic waves and account for less than 1 percent of decays.
Alpha particles have a range of about 10 microns in material such as skin or table salt and can pass through some materials that block other forms of radiation. They can also be emitted when an atomic nucleus transforms itself from one state to another, usually by adding or removing one or more neutrons. An example is when a uranium atom changes into a lead atom without adding any neutrons. This change occurs because of the presence of neutrons in the nucleus of the uranium atom but not in the lead atom; thus, it requires alpha particle emission to balance out the number of neutrons and protons. A second type of alpha particle emission happens when two neutrons collide with each other inside a nucleus producing two new neutrons which can then escape the nucleus forming two helium atoms instead. This process, known as neutron decay, accounts for most of the alpha particles emitted by radon gas.
Radiation and radioactive emissions come in a variety of forms. The information presented here only covers the four most frequent types: alpha particles, beta particles, gamma rays, and X-rays.
They are the most common type of radiation emitted by atomic nuclei. An alpha particle has a mass about 4% of a proton, so it is very light and can travel great distances before losing energy through other means such as electron capture or interaction with atoms. In fact, an alpha particle can pass completely through a typical sheet of paper.
Beta particles are electrons ejected from an atom when it undergoes a radioactive decay. On average, every nucleus emits two beta particles, one from each parent nucleus. But some nuclei emit more than two particles, others less; it depends on the particular element involved and the energy level of its nucleus. For example, uranium emits alpha particles and plutonium emits beta particles.
Gamma rays are electromagnetic waves that consist of photons (light particles) with energy equal to that of a radio wave but with the added advantage of being able to penetrate deep into solid objects. Because they have a high frequency, they can pass straight through dense material like air or water without much interaction. When they reach something denser than air, like bone, they are partially absorbed.