When a black car is in the sun, it gets warm because the color black absorbs the energy of the sun’s rays. White stays coolest because it reflects all colors. What about the rest of the colors? Does the temperature gradually increase the darker the color is? Or does a certain color absorb more heat? For example, blue, yellow, red or infrared or ultraviolet?
Answer
under irradiation by the sun, a perfectly black object absorbs all the energy contained in the (visible +…) part of the light. A perfectly white object nothing. So a black object will heat up faster than a white one, and objects with other colors will heat up at an intermediate rate. Dark colors will warm up faster than light ones.
How fast depends on the relative amount of radiation of different wavelengths in the light. This varies quite a bit from light source to light source.
For each wavelength individually, it can be absorbed more or less by an object with a certain “color”. So there is no wavelength or type of light that is absorbed less or more. There is a difference in the amount of light of a certain wavelength that is present in the light.
Sunlight contains light from UV to near infrared (NIR) with a maximum near the green wavelengths (see URL). Due to the absorption of the atmosphere, there is almost no UV in it at low altitudes, but there is at high altitudes.
Incandescent light contains relatively much more NIR and almost no blue or UV.
Fluorescent and LED light are optimized to shine only visible light, and almost no UV or NIR.
Answered by
Engineer Bart Dierickx
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