These two photographs of a flower show how the evening primrose looks in two different wavelengths. The upper panel shows the flower as humans see it in visible light. The lower panel shows the primrose in UV, and reveals the "honey guides" (the dark areas) invisible to the human eye but seen by insects. The dark lines and patches guide the insect to the collection of nectar stored in the center and to the pollen on the anthers.
Image courtesy Dr. Jeremy Burgess, Science Source/Photo Researchers.
Ultraviolet (UV) Radiation
Ultraviolet (UV) "light" is a type of electromagnetic
radiation. UV light has a shorter wavelength than visible
light. Purple and violet light have shorter wavelengths than other
colors of light, and
ultraviolet has even shorter waves than violet does; so ultraviolet is sort of "purpler-than-purple" light
or "beyond violet" light.
Ultraviolet radiation lies between visible light and X-rays on the electromagnetic
spectrum. UV "light" has wavelengths between about 380 and 10
nanometers. The wavelength of violet light is around 400 nanometers (or 4,000 ┼).
Ultraviolet radiation oscillates at rates between about 800
terahertz (THz or 1012 hertz)
and 30,000 THz.
The ultraviolet spectrum is sometimes subdivided into the near UV (380
to 200 nanometer wavelengths) and extreme UV (200 to 10 nm wavelengths). Normal
air is largely opaque to UV with wavelengths shorter than 200 nm (the extreme
UV range); oxygen absorbs "light" in that part of the UV spectrum.
of impact on the environment and human health (and choosing sunglasses!),
UV spectrum in a
way, into UV-A
Wave UV with a 380 to 315 nm wavelength), UV-B (Medium Wave at 315 to 280
nm), and UV-C (the "germicidal" or Short Wave UV that ranges from
280 to 10 nm).
Earth's atmosphere prevents most UV
radiation from space from reaching the ground. UV-C is entirely screened out
by stratospheric ozone at around 35 km altitude. Most UV-A does reach the
surface, but UV-A does little
genetic damage to tissues. UV-B is largely responsible for sunburn and skin
cancer, though it is mostly absorbed by ozone before reaching the surface.
Levels of UV-B radiation at the surface are especially sensitive to levels
of ozone in the stratosphere.
Ultraviolet radiation causes sunburn. It is used to
sterilize glassware used
in medicine and biological research.
Shop Windows to the Universe Science Store!
Learn about Earth and space science, and have fun while doing it! The games
section of our online store
includes a climate change card game
and the Traveling Nitrogen game
You might also be interested in:
Electromagnetic radiation is the result of oscillating electric and magnetic fields. The wave of energy generated by such vibrations moves through space at the speed of light. And well it should... for...more
About 90% of the ozone in the Earth's atmosphere is found in the region called the stratosphere. This is the atmospheric layer between 16 and 48 kilometers (10 and 30 miles) above the Earth's surface....more
The thermosphere is a layer of Earth's atmosphere. The thermosphere is directly above the mesosphere and below the exosphere. It extends from about 90 km (56 miles) to between 500 and 1,000 km (311 to...more
Solar Dynamics Observatory (SDO) is a satellite which studies the Sun. SDO carries several telescopes and other instruments for observing the Sun. The instruments on SDO take much better pictures than...more
Have you ever seen the Southern or Northern Lights? Earth isn't the only planet that puts on these beautiful light shows, which are also called the "aurora". Aurora have been seen at both poles of Saturn,...more
The Hubble Space Telescope (HST) was one of the most important exploration tools of the past two decades, and will continue to serve as a great resource well into the new millennium. The HST found numerous...more
Earth's magnetosphere shields our planet from most of the solar wind. Some solar wind particles do leak in and combine with ions escaping from the top of Earth's atmosphere to populate the magnetosphere...more