MadSci Network: Astronomy
Query:

Re: how does the color of a background affect its absorption of solar insulation

Date: Fri Apr 28 22:38:07 2000
Posted By: Dan Patel, Undergraduate, Chemistry Major/Math Minor, University of Houston
Area of science: Astronomy
ID: 955145216.As
Message:

I think you may be asking how color affects the absorption of solar radiation. Radiation is just a fancy word for light---any kind of light, even light that the human eye cannot see. In fact, there are several things that can affect how an object absorbs radiation. Color is just one of those things.

Temperature is one of the things that color can affect. We know that a black object usually gets hotter than a white object, but why? That's because a black object absorbs all the light that hits it, and a white object will reflect most of the light that hits it.

If we mix all the colors of the rainbow we get white light---just like the light you see from a light bulb. A leaf is green because it absorbs all colors except green---the leaf reflects green light. The same is true for other colors. A rose is red because the petals absorb all colors except red---red light is reflected, and a black object is black because it does not reflect any light (or if it does, it reflects very little light).

Because light is just a type of energy, the more light something absorbs, the hotter it will get. Black objects absorb more light than white objects, that's why they get hotter.

[This question is also one that can be answered by experiment. Find a couple of thermometers. On a sunny day, place them outside on different colored sheets of paper, e.g., blue and red. Which thermometer records the higher temperature? Moderator]


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