The World Health Organization created the UV Index to measure the amount of harmful UV light entering the earth’s atmosphere. The index measures UVA and UVB waves, which are more dangerous to skin and eyes than visible light. Factors affecting UV levels include the position of the sun, atmospheric conditions, and soil reflection. To limit exposure, individuals can wear sunglasses and sunscreen, seek shade, and cover their skin.
Many scientists suggest that ultraviolet (UV) light waves from the sun are harmful to human skin and eye tissue. As a result, the World Health Organization (WHO) created the UV Index – a standard system for measuring the amount of UV light entering the earth’s atmosphere. The linear scale is a way for governments and scientists to measure and monitor the intensity of ultraviolet light, as well as warn the public about the potential dangers associated with high levels of UV.
UV radiation is a specific set of wavelengths on the light spectrum. The waves are shorter than visible light. Often classified as UVA and UVB, these light waves are generally considered to be more dangerous to the skin and eyes than visible light. The UV index measures how much of these potentially harmful waves reach the lower atmosphere.
There are several factors that affect ultraviolet light in a given area. First, the position of the sun in the sky often matters. The seasons can affect UV by changing the distance from the sun and the angle of light from the Earth. Also, UV rays are often strongest at latitudes closer to the equator.
For the most part, the UV index measures the intensity of light waves at solar noon, or the time of day when the sun is highest in the sky. Sunlight is typically strongest at this time. Solar noon may not be the same as noon on a clock.
Secondly, atmospheric conditions can also affect ultraviolet levels. A denser atmosphere results in lower radiation, so the UV index level is often different from mountain to valley. Cloud cover can also have an effect, but it doesn’t make a big change, because UV radiation can typically penetrate clouds better than other wavelengths of light. Additionally, ozone in the upper atmosphere can filter out harmful UV rays.
Finally, soil reflection may also play a role in the UV index. Snow, water and sand can all reflect UV light. This reflection can intensify the level of ultraviolet rays affecting an individual outdoors under these conditions because they not only receive UV rays directly from the sun, but they are reflected off the ground.
There are several ways to limit an individual’s exposure to UV light. Sunglasses with UVA and UVB filters can protect a person’s eyes from harmful rays. Sunscreens with at least sun protection factor (SPF) 15 are often recommended to protect the skin.
Individuals may also want to seek shade, stay indoors, or at least avoid direct sunlight during peak sunshine hours. Depending on your time zone, this period usually falls between 10am and 4am. People may also want to cover their skin by wearing long sleeves, pants, and a wide-brimmed hat.
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