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Q & A: color and light energy

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Most recent answer: 10/22/2007
Q:
If the frequency of light determines the energy it contains, then certain colors we see contain different amounts of energy. Is this true or false? If it is true, what color would emit (or transmit) the most energy? Would identical fish living in identical conditions in an aquarium grow differently under different frequencies (colors) of light? If so, would our world be completely different if our atmosphere allowed more or less frequencies of light to be transmitted onto the earths surface?
- Mark Yutan (age 25)
Los Angeles, CA
A:
Mark- Interesting questions. Actually, there can be lots of energy or very litle energy in any color of light. One of the peculiarities of quantum mechanics, though, is that the energy comes in lumps of different sizes, depending on the frequency. When a molecule absorbs light, the amount of energy absorbed in one step is twice as big for twice as high a frequency.

I don't know how much different types of fish are affected by light of different colors.

Certainly if the atmosphere let different frequencies of light through, the world would be very different. Plants, for example, are specialized to use the frequencies that reach them to make chemical energy (via photosynthesis).
In fact, human activity has changed the frequencies of light that reach us because pollutants reduce the ozone level in the upper atmosphere, allowing more ultraviolet light through than before. That certainly causes more skin cancers, and may have other very serious bad effects for various types of life. Fortunately, international treaties have reduced the amount of the worst ozone-destroying pollutants, so this problem may gradually get less severe.

Mike W.

(published on 10/22/2007)

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