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In physics, radiation is the emission or transmission of energy in the form of waves or particles through space or through a material medium.[1][2]

This includes:

  1. electromagnetic radiation such as radio waves, visible light, and x-rays
  2. particle radiation such as α, β, and neutron radiation
  3. acoustic radiation such as ultrasound, sound
  4. seismic waves.

Radiation may also refer to the energy, waves, or particles being radiated.

Electromagnetic radiation[change | change source]

Many people are already familiar with electromagnetic radiation (EMR) including light. Electromagnetic radiation is categorized based on its wavelength and frequency. Some kinds are:

  • Ionizing radiation comes from radioactive materials and x-ray machines and non-ionizing radiation (usually electromagnetic radiation) comes from other sources. Ionizing radiation carries more than 10 eV (electronvolt), which is enough to ionize atoms and molecules, and break chemical bonds. This is important for its harmfulness to living organisms. Non-ionizing radiation does not cause microscopic damage, but some types can cause chemical changes or make things hotter.
    • X-rays and Gamma rays: These very strong rays are commonly used in medicine to photograph the interior of the body and treat cancer. However, in too large amounts, they are very dangerous to life.
    • Ultraviolet light: This is a type of radiation with more energy than visible light. It gives people a sunburn. Ultraviolet light is used to kill bacteria and to make some kinds of invisible ink visible.
  • Visible light: This is the radiation that we see all around us as what most people call "light."
  • Infrared waves: Most objects at room temperature let off infrared radiation. Although humans cannot see it, special types of cameras can pick up this kind of radiation. Usually, the hotter something is, the more infrared radiation it lets off, which means that these special cameras can see hot things, even behind walls.
  • Radio waves: This is the kind of electromagnetic radiation with the longest waves. Radio waves are used to send and receive communications.
    • Micro-waves: This is a special kind of radio wave that is used by a microwave oven to warm up food. Microwaves are also used for communications, as weapons, and to move electrical power from one place to another.
    • Radar waves: This is also a kind of radio wave that is used to detect air planes in the sky and ships in the ocean. Radar is also used to see changes in weather.

Danger from radiation[change | change source]

ionizing radiation is radiation that carries enough energy to free electrons from atoms or molecules.

Only certain types of radiation are harmful to humans. For example, ultraviolet radiation can give people sunburns. X-rays and gamma rays can make a person sick, or even die, depending on the dose they get. Some types of particle radiation can also make people sick and lead to burns. If radiation does not carry high enough levels of energy, though, then these changes will not happen when something is hit by the radiation. This is referred to as non-ionizing radiation, which is not as dangerous.

One can distinguish between various types of radiation by looking at the source of the radiation, its wavelength (if the radiation is electromagnetic), the amount of energy being carried, any particles involved, etc. Radioactive material is a material which emits radiation. Uranium and plutonium are examples of radioactive materials. The atoms they are made of tend to fall apart and give off different kinds of radiation, like gamma rays and lots of particle radiation.

Ionizing radiation by type[change | change source]

Ionizing radiation can kill living things. It can cause genetic mutations, as shown by H.J. Muller. It can destroy cells in the body which divide, and thus indirectly kill a person.

Non-ionizing radiation by type[change | change source]

Related pages[change | change source]

References[change | change source]

  1. Weisstein, Eric W. "Radiation". Eric Weisstein's World of Physics. Wolfram Research. Retrieved 2014-01-11.
  2. "Radiation". The free dictionary by Farlex. Farlex, Inc. Retrieved 2014-01-11.