Student Question

Why do dark colors absorb more heat and light than light colors?

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When light comes to us from the sun, we call it "white light" because it contains all the visible light spectrum colors available, those being red, orange, yellow, green, blue indigo, and violet.  All these colors combine to make white light.  We know this because we can take a prism and shine white light through it, and it will break the light up into the individual colors that make it up.

Objects that are black are absent of any of the visible light spectrum colors.  So when those objects are radiated upon by light, none of the individual wave lengths are reflected.  They are all absorbed, which translates to increased heat and temperature.

Conversely, items that are white or light colored, reflect most, if not all the wavelengths contained in the visible light spectrum.  So they are reflected away from that object, which translates into same heat, same temperature.

So when you go outside, if it is hot, wear light-colored clothing; it will absorb less of the sun's radiation.  If it is cold, wear dark-colored clothing; it will absorb more of the sun's radiation. Of course, this becomes complicated and changes if wind and tightness or looseness of clothing are factors. Just think of all the white animals with fluffy fur or feathers in the Arctic and Antarctic.

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Why do dark objects absorb more heat and light?    

Heat and light are both forms of energy. Therefore, in terms of the object absorbing more heat and light what is really being observed is dark objects absorbing more energy. Light energy can be transferred into heat by exciting molecules in an object which has absorbed it, leading directly to increased heating in that object. This phenomenon is why dark objects will have get hotter than lighter ones. Different wavelengths of light contain different amounts of energy. Shorter wavelengths of light, such as violet, contain more energy than longer wavelengths of light, such as red. This means an object that absorbed violet wavelengths of light will absorb more energy than an object that absorbed red wavelengths of light, and thus have more energy to transfer into the form of heat. 

Lets take black objects for example. Black objects absorb all wavelengths of the color spectrum. White objects on the other hand, reflects all wavelengths of the color spectrum. Because dark objects absorb more wavelengths of light, they also absorb more energy. This energy from light causes molecules in the object to move more rapidly, generating heat. In the example of a white object, this does not happen because the object is reflecting all the wavelengths of light and the molecules inside the object are not being excited. Since no light energy is absorbed, no heat is generated. Hope this helps!

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Why do dark colors absorb more heat and light than lighter colors?

Visible light is composed of all the colors in the spectrum of visible light, those being red, orange, yellow, green, blue, violet, and indigo.  Those all combine together to produce white light.  Objects that are black, or appear black, will not reflect any of those wavelengths, they absorb them rather than reflect them.  This transfers to increased radiation absorption, which causes increased thermal reaction.  Objects that are lighter in color, or white, reflect most or all of those wavelengths and tend to have less radiation absorption, so they have less thermal reaction.

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