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Albedo body


 

A high albedo surface reflects 80% of incoming radiation.  The low albedo surface reflects only 10% of incoming radiation.

Figure A

The amount of energy that is reflected by a surface is determined by the reflectivity of that surface, called the albedo.  A high albedo means the surface reflects the majority of the radiation that hits it and absorbs the rest.  A low albedo means a surface reflects a small amount of the incoming radiation and absorbs the rest.  For instance, fresh snow reflects up to 95% of the incoming radiation.  Therefore, fresh snow has a high albedo of .95.  By contrast, water reflects about 10% of the incoming radiation, resulting in a low albedo of .10.  Since 30% of the sun’s energy is reflected by the entire earth, the earth has an average albedo of .30.  Generally, dark surfaces have a low albedo and light surfaces have a high albedo.  For example, in summer the black asphalt road is scorching hot. This is because much of the heat is absorbed by the asphalt allowing the asphalt to burn your feet as you walk on it. When it’s hot outside, lighter clothing keeps you cooler because it reflects most of the sunlight that hits it, keeping you cool. Keep in mind that it is still possible to get sunburnt while wearing a light colored shirt with no sunscreen underneath. Although much of the incoming radiation is reflected, there is still quite a bit that is absorbed by the shirt.

Last modified date: Monday, July 30, 2012 - 10:33am