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Generally speaking, heat transfers in three different ways: convection, conduction and radiation. Radiation is the process by which energy is transmitted through space without significant loss. This radiant energy is transfeited from source (emitter) to receive (absorber) in the form of electromagnetic waves. While being transmitted in this way, this energy is called radiant energy and is not in the form of heat.
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Heat is the result of absorption of radiant energy by matter. Radiation energy does not affect bodies or material substances through which it passes or reflects, but affects only those that have absorbed it. When radiation does come in contact which materials that absorb it, the radiation is converted into heat, thus raising the temperature of the absorbing material. Therefore, it has the property of heating an object directly without heating the surrounding air. As such, radiation is markedly different from thetransmission of heat by means of convection and conduction because the latter ones require the media of solids, liquids, vapors or gases or transfer the energy from the source to its final destination(object).
Some common examples of radiant heat sources are the sun, glowing embers in a fire, hot stones and an electric toaster. Even the human body radiates to its surroundings--usually at a rate of about 400 BTU per hour. Thus infrared heat waves are harmless and should not be confused with ultraviolet radiation or atomic radiation, which can be injurious. Infrared is a safe and useful form of radiant energy. The sun, of course, is the best -known source.
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| Difference between Infrared and Far Infrared |
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Infrared rays are waves of energy. Since they are partly electric and partly magnetic, the are members of the electromagnetic family. Infrared is the band beyond visible radiant energy occurring between the visible red end of the electromagnetic spectrum and the outer band of radio waves.
Infrared rays have a frequency which extends from approximately five hundred million megacycles to three million megacycles. The name and the effect of the infrared rays are various according to the length of wave. The spectrum of the infrared ray is 0.75 to 1000μ(micron). Infrared radiation is classified as near or far. The near infrared region is usually in the 0.75 to 2.5μ rane while the far infrared radiation is in the 2.5 to 1000μ range. |
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