Radiant energy exists in a range of wavelengths that extends from radio waves that many be thousands of meters long to gamma rays with wavelengths as short as a million-millionth (10-12) of a meter.
Of particular importance to living things are
The shorter wavelengths of ultraviolet can be absorbed by DNA and damage it — causing mutations.X-rays and gamma rays also damage DNA by generating ions within the cell. Thus these wavelengths represent ionizing radiation.
|Link to a discussion of ionizing radiation.|
Light makes possible a number of essential functions in living things:
Approximately one-half of the energy reaching the earth from the sun is light; that is, it is within the visible portion of the spectrum. The remainder arrives as heat and a small amount of ultraviolet light (which can, however, have a large effect on the aging of skin and the development of skin cancer).
|Link to more on the input of the sun's energy on earth.|
|Link to a discussion of the relationship between ozone in the stratosphere and the amount of UV-B reaching the earth.|
|Link to a discussion of radiation and cancer.|