Radiation
Article by: Christopher S. Baird, Department of Chemistry and Physics, West Texas A & M University, Canyon, Texas.
Content
• Electromagnetic radiation
• Particle radiation
• Acoustic radiation
• Gravitational radiation
• Ionizing versus non-ionizing radiation
Key Concepts
• Radiation involves the emission and propagation
of particles or waves.
• The major types of radiation are electromagnetic, particle,
acoustic, and gravitational.
• Electromagnetic radiation consists of photons.
• Particle radiation consists of rapidly moving particles.
• Acoustic radiation, or sound, consists of traveling patterns
of vibration in a medium.
• Gravitational radiation consists of traveling patterns of
spacetime curvature.
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The
emission and outward propagation of energy-carrying
particles or waves; also, the emitted particles or waves
themselves. Radiation is a common phenomenon that
transfers energy, matter, momentum, and information from
one place to another. The major types of radiation are
electromagnetic radiation (Fig. 1), particle radiation, acoustic
radiation, and gravitational radiation. Generally speaking, any
particle or wave can become radiation if it is emitted from a
source and then propagates directly away from its source. In
science, the word "radiation" is used in this general sense and
does not nec-essarily imply that the particle or wave is
harmful. Radiation that is directly harmful is referred to as
ionizing radiation. Only ionizing radiation can, depending on
the exposure, directly cause radiation sickness, mutation, and
cancer. Radiation tends to travel in straight lines through
space as it propagates away from its source. Radiation
continues to propagate in this way until it encounters and
interacts with a physical object. Through this interaction, the
radiation can transfer to the object some or all of its energy,
matter, momentum, or infor-mation. In the situation where all
of the radiation is traveling generally in the same direction,
the radiation is referred to as a beam. For instance, the
radiation from a laser is known as a laser beam. Similarly, the
radiation from a proton accelerator is known as a proton
beam.
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Fig. 1: Crepuscular rays, which are shafts of air illuminated by electromagnetic radiation
(light) radiating from the Sun. [Credit: Danny Chapman / Flickr/ Attribution-ShareAlike 2.0
Generic ( CC BY-SA 2.0 )]
