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The UV index is a number linearly related to the intensity of sunburn-producing UV radiation at a given point on the Earth's surface. It cannot be simply related to the irradiance (measured in W / m 2 ) because the UV of greatest concern occupies a spectrum of wavelengths from 295 to 325 nm, and shorter wavelengths have already been absorbed a ...
A relatively new rating designation for sun protective textiles and clothing is UPF (ultraviolet protection factor), which represents the ratio of sunburn-causing UV measured without and with the protection of the fabric. For example, a fabric rated UPF 30 means that, if 30 units of UV fall on the fabric, only 1 unit will pass through to the skin.
The sun protection factor (SPF rating, introduced in 1974) is a measure of the fraction of sunburn-producing UV rays that reach the skin. For example, "SPF 15" means that 1 ⁄ 15 of the burning radiation will reach the skin, assuming sunscreen is applied evenly at a thick dosage of 2 milligrams per square centimeter [65] (mg/cm 2). It is ...
The latest TikTok tanning trend involves monitoring the UV index and timing sunbathing sessions to when it's high, but experts say that exposing yourself to strong ultraviolet rays is a bad idea.
Ultraviolet radiation, also known as simply UV, is electromagnetic radiation of wavelengths of 10–400 nanometers, shorter than that of visible light, but longer than X-rays. UV radiation is present in sunlight, and constitutes about 10% of the total electromagnetic radiation output from the Sun.
SPF rating: 30 | Sunscreen type: mineral | Fragrance-free: yes ... EltaMD UV Active Broad-Spectrum SPF 50 $ at Dermstore. ... USA TODAY Sports.
Extreme UV and X-rays are produced (left of wavelength range) but comprise very small amounts of the Sun's total output power (area under the curve). Although the solar corona is a source of extreme ultraviolet and X-ray radiation, these rays make up only a very small amount of the power output of the Sun (see spectrum at right).
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