I am in an HVAC/R technician certification class, and the instructor taught us that radiant heat energy only increases the temperature of solid objects, and the temperature of gases are not affected by radiant heat energy. Is this true? Electromagnetic waves have no affect of any kind on the temperature of any of the gases that make up the air in and around our homes?
1 Answer
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Radiant heat energy is light, usually of wavelengths too long for you to see. If you heat an object hot enough, it glows red hot. That is, it gives off red light. It also gives off infrared. If you heat it less, the only light is the longer wavelength infrared.
When light hits an object, it might be reflected away, transmitted through, or absorbed. If reflected or transmitted, the light and its energy leave the object. If absorbed, the energy stays inside the object and heats it up. This is why objects get warmer if left sitting in the sun. A flashlight will do the same thing, but the temperature change is too small to notice.
Sometimes part of the light does one thing and the rest does another. For example, a blue object reflects blue light, and absorbs other colors.
The gasses in air are transparent in visible wavelengths. Visible light passes through without heating them. The same is true of near infrared light. Longer wavelength light is absorbed to a degree. But not very much energy is in those wavelengths. Air is not heated that way enough to notice.
answered Mar 22, 2022 at 15:59
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$\begingroup$ This current answer seems to address the question only qualitatively (in binary terms), and only in the last paragraph. It might be more useful if the actual transmittance over the spectrum were discussed (shown here for a distance of one nautical mile, for example). Then a connection could be made between the distances over which we do see notable absorption and the distances associated with the geometry of a typical house. $\endgroup$ Commented Mar 22, 2022 at 17:17