I store the link to this extraordinary beautiful and clear image of Andromeda here for easy of reference later on as the APOD site has so many images.
UV light
Ultraviolet (UV) light is electromagnetic radiation with a wavelength shorter than that of visible light, but longer than X-rays, in the range 10 nm to 400 nm, and energies from 3 eV to 124 eV.
It is named because the spectrum consists of electromagnetic waves with frequencies higher than those that humans identify as the colour violet. These frequencies are invisible to humans, but visible to a number of insects and birds. They are also indirectly visible, by causing fluorescent materials to glow with visible light.
Although ultraviolet radiation is invisible to the human eye, most people are aware of the effects of UV through sunburn, and in tanning beds. A great deal (>97%) of mid-range ultraviolet (almost all UV above 280 nm and most above 315 nm) is blocked by the ozone layer, and would cause much damage to living organisms if it penetrated the atmosphere.
After atmospheric filtering, only about 3% of the total energy of sunlight at the zenith is ultraviolet, and much of this is near-ultraviolet that does not cause sunburn. An even smaller fraction is responsible for sunburn and also the formation of vitamin D (peak production occurring between 295 and 297 nm) in all organisms that make this vitamin (including humans).
The UV spectrum thus has many effects, both beneficial and damaging, to human health.
wikipedia
It is named because the spectrum consists of electromagnetic waves with frequencies higher than those that humans identify as the colour violet. These frequencies are invisible to humans, but visible to a number of insects and birds. They are also indirectly visible, by causing fluorescent materials to glow with visible light.
Although ultraviolet radiation is invisible to the human eye, most people are aware of the effects of UV through sunburn, and in tanning beds. A great deal (>97%) of mid-range ultraviolet (almost all UV above 280 nm and most above 315 nm) is blocked by the ozone layer, and would cause much damage to living organisms if it penetrated the atmosphere.
After atmospheric filtering, only about 3% of the total energy of sunlight at the zenith is ultraviolet, and much of this is near-ultraviolet that does not cause sunburn. An even smaller fraction is responsible for sunburn and also the formation of vitamin D (peak production occurring between 295 and 297 nm) in all organisms that make this vitamin (including humans).
The UV spectrum thus has many effects, both beneficial and damaging, to human health.
wikipedia
No comments:
Post a Comment