ULTRAVIOLET. 1 P a g e

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Noel McCoy
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1 ULTRAVIOLET Often called black light, ultraviolet radiation is invisible to the human eye, but when it falls on certain surfaces, it causes them to fluoresce, or emit visible light. That portion of the electromagnetic spectrum adjacent to the short wavelength, or violet, end of the visible light range, is called ultraviolet radiation. 1 P a g e

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4 Sunburn is a painful inflammation of the skin that is caused by overexposure to the invisible ultraviolet rays of the sun. Sunburn ranges from mild redness that disappears in a few hours to blistering, swollen, scarlet skin that peels before it heals. A severe sunburn can cause chills, dizziness, fever, and weakness. Repeated, prolonged exposure to the sun also can lead to premature aging of the skin and to skin cancer. The seriousness of a sunburn depends on the intensity of the light and the length of time spent in the sun. The sun's burning rays shine most intensely during the summer and from late morning to early afternoon. They travel through clouds and water, and so a person can be burned on a cloudy day or while swimming. Sand and snow reflect the rays and increase the chances of being burned on a beach or ski slope. The skin contains a brown-black pigment called melanin, which partially provides natural protection from sunburn. Blue-eyed blonds, redheads with freckles, and other fair-skinned people have little melanin and burn easily. However, dark-skinned people rarely burn because their skin has much more melanin. Most fair-skinned people can tan without burning if they stay in the sun for only 15 minutes the first day and then increase the time by 10 to 15 minutes daily. Sunburn can also be avoided by covering the skin or by using a lotion containing chemicals that act as a sun block or a sunscreen. A sun block filters out all the sun's burning rays, and a sunscreen filters most of them. Commercial sunscreens are available in various strengths indicated by a number called a sun protection factor (SPF). An SPF of 2 means that, once applied, twice the normal time passes before the skin becomes sunburned. Skin experts recommend that fair-skinned people use a sunscreen with an SPF of 15 or higher. Darkerskinned people may use one with a lower SPF. Sunscreens should be applied 15 to 20 minutes before prolonged exposure to the sun and should be reapplied frequently. The best treatment for sunburn is aspirin, which relieves the pain and reduces the inflammation. Cool baths, wet compresses, and medicated creams also provide relief. Critically reviewed by the American Red Cross 4 P a g e

The Ozone Layer Even though only about 5 percent of the electromagnetic radiation emitted by the sun is ultraviolet, that amount would be sufficient to severely damage most forms of life on Earth if

5 The Ozone Layer Even though only about 5 percent of the electromagnetic radiation emitted by the sun is ultraviolet, that amount would be sufficient to severely damage most forms of life on Earth if all of it reached the surface of the Earth. Fortunately, a layer of oxygen in the atmosphere at an altitude of about 15 miles (24 kilometers), called the ozone layer, absorbs nearly all of the far ultraviolet radiation and much of the near ultraviolet radiation. The energy of the ultraviolet light turns atmospheric oxygen into ozone, which is oxygen with three atoms in each molecule; oxygen normally only has two atoms to the molecule. Recently, however, because of certain emissions from factories on Earth and other sources, the ozone layer over parts of the Earth has been rapidly thinning or completely disappearing. Although efforts are being made to stem the emissions, if ozone depletion were to continue at the present rate which is faster than ultraviolet light can create ozone the incidence of cancer, certain eye diseases, and other ailments could rise significantly among people in most regions of the world. Specialized Microscopes Before the invention of electron microscopes, continuous effort was made to increase the resolution of the microscope by using shorter and shorter wavelengths, moving into the invisible ultraviolet region of the spectrum. Ultraviolet microscopes, used in medical research, produce photomicrographs, which reveal details that visible rays would pass over without reflection or refraction. With other developments, such as specialized glass filters, ultraviolet light is also used for excitation of fluorescence to convert ultraviolet light to visible light under a microscope. Bees There are more than 20,000 bee species, and they are found in every part of the world except in Antarctica. Most people throughout the world recognize honeybees, and people in temperate regions know bumblebees as well. Ordinarily, most bees fly about 12 1 / 2 miles (20 kilometers) per hour, but they can fly much faster. They have two pairs of wings. One pair is attached to each of the last two segments of the thorax, but front and back wings are joined so that they may look like only one. The rapid movements of the wings make a humming sound in flight. With three single eyes on top of their heads and two huge, helmet like compound eyes, bees can see color, pattern, and movement. The many facets of their compound eyes give them a total image in a mosaic of dots. Bees see all colors humans do except red, and they see ultraviolet, which humans cannot. Ultraviolet is often reflected by red flowers. Bees can also detect the polarization of light, which humans cannot. For example, in a blue sky polarized light forms a distinctive pattern around the Sun, and even when the Sun is behind the clouds bees can perceive that pattern and orient themselves to it. Attracted by both color and shape, bees show a strong preference for flowers with elaborate embellishments and respond readily to patterns of color, particularly in hues of yellow, blue, and ultraviolet. A more deeply shaded pattern is present near the center of some blossoms. This clearly marked area acts as a carpet of color to guide the bee to the nectar. The liplike petals of many flowers provide a place where a bee can land before entering. When a bumblebee alights on the lip of a snapdragon, the bumblebee s weight, which is greater than that of most bees, opens the flower s mouth, letting the bee enter the inner chamber to sip the nectar. 5 P a g e

6 First Fluorescent Frog World Book Online Behind the Headlines Mar 24, 2017, n.p. If you are lucky enough to go camping along the banks of the Paraná River in the Argentine Pampas of South America, be sure to carry an ultraviolet (UV) flashlight with you. Among the leaves, vines, and creepy crawlies, you just might find glow-in-the-dark frogs! A couple of weeks ago, a team of researchers from the University of Buenos Aires and Brazil's University of São Paulo discovered the first fluorescent frog near Santa Fe, a city in northeastern Argentina. Yes, these frogs can create their own light! This first fluorescent frog, the polka dot tree frog, is already well-known and commonly found throughout the Pampas and the nearby Amazon Basin, so it is not a new species. But scientists did not know the amphibians had fluorescent "power" until now. The capability to absorb light at short wavelengths and re-emit it at longer wavelengths is called fluorescence. It is uncertain why some animals have this ability, but it may be used to communicate, for camouflage, or to attract a mate. Fluorescence is fairly common in the ocean, where fish, plankton, and even sea turtles can emit their own light. In the desert, scorpions also glow in the dark. But never before has anyone seen a phosphorescent amphibian. Scientists found that the 1.2-inch (3-centimeter) polka dot tree frog's glowing ability come from a compound found in the lymph and skin glands of its translucent (see-through) body. The fluorescence does not work in complete darkness, but rather at twilight, when the frog's skin has recently absorbed light, and its color goes from a dull pale green with speckled white, yellow, or reddish spots, to a bright green with dark spots. There are thousands of frog species around the world, and they live on every continent except Antarctica. If you pay attention, you'll notice that new frog species are discovered fairly often. Their sometimes tiny size and reclusive habits in the remotest of forests make some frogs extremely hard to find. The polka dot tree frog may be the first fluorescent frog known to science, but the ever-evolving natural world is bound to be hiding others in the darkest corners of Earth--just keep your UV light on and your eyes open! "First Fluorescent Frog."SIRS Discoverer, 24 Mar, 2017, 6 P a g e

Your Kids and the Sun

Your Kids and the Sun Please click on any of the links below to go directly to your specified topic within this document. How Does the Sun Harm Our Skin? Some Skin Cancers Can Be Deadly Childhood Sun Protection