What are Ultraviolet Rays?
Have you ever looked at the sunbeam coming through the windows while you are taking your physics tuition? If not, you definitely felt them over your shoulder while taking a walk down the street on a sunny morning? Have you given a thought to the composition of the sunlight? When the sunlight is allowed to pass through a prism, it splits into seven colors. These colors are violet, indigo, blue, green, yellow, orange and red. Wavelength wise distribution of these seven colors is known as a spectrum. Light travels in the form of waves. These waves are produced due to electrical oscillations.
In the seven colors of the sun’s spectrum, the wavelength of the violet color is minimum while that of red is maximum. The observed wavelengths in the visible spectrum range from about 7.5 x 10-5 cm to 4 x 10 -5 cm. Radiations having a wavelength less than violet color (4x 10-5) are known as Ultraviolet (UV) Rays. The energy associated with UV rays is quite high. Overexposure to UV rays can cause skin burns and may even lead to skin cancer. The sun produces a large number of UV rays. But, most of it is absorbed by a layer of gas called ozone in the upper atmosphere of the earth, due to which very small amount reaches the earth. If the entire amount of UV rays were to reach us, life would not have been possible on earth.
Ultraviolet (UV) light falls in the range of the EM spectrum between visible light and X-rays. It has frequencies of about 8 x 10^14 to 3 x 10^16 cycles per second, or hertz(Hz), and wavelengths of about 380 nanometres (1.5 x 10^-5 inches) to about 10 nm (4 x 10^-7 inches).
UV is generally divided into three sub-bands.
- UVA, or near UV (315-400 nm)
- UVB, or middle UV (280-315 nm)
- UVC, or far UV (180-280 nm)
Ultraviolet rays are also quite useful but to a smaller extent. They kill certain bacteria and help change certain chemicals in the skin into vitamin D. But, these rays are extremely harmful to eyes. While working with ultraviolet light one must wear colored glasses. So, next time you are playing or roaming under the scorching sun, remember your physics tuition lessons and be prepared to wear a brimmed hat and sunglasses.
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