By Dr. Stuart Mitchell
Sunlight takes 8 minutes and 17 seconds to reach the Earth. Sunlight consists of 30% visible light, 56% infrared light, 5% ultraviolet light, and other wavelengths. Of the ultraviolet light (UV), 98% is longer wave UV-A. Ultraviolet (“beyond violet”) rays are electromagnetic radiation in wavelengths of 0.39 to 0.032 micrometers (10−6 meters) or 400 nm to 10 nm (10−9 meters).
To investigate the existence of energy beyond the violet end of the visible spectrum, Johann Ritter conducted an experiment in 1801. Aware that photographic paper turns black quicker in blue light than in red light, Johann exposed the paper to light beyond violet. The paper turned black, proving the existence of ultraviolet light.
The classifications used in Earth sciences subdivide UV into UV-A, UV-B, and UV-C. UV-B rays are injurious, causing sunburn. UV-B ray exposure increases the risk of DNA and cellular damage within living organisms. Ozone in the Earth’s atmosphere absorbs about 95 percent of UV-B rays. The most dangerous and completely absorbed by our atmosphere are UV-C rays.
Although UV waves are invisible to the human eye, insects (such as House fly), birds, and reptiles can see UV-A light reflecting off of plants. Using UV-A light, ILT and EFK systems lure and trap both disease spreading and destructive flying insects.
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