Ultraviolet Rays


High Frequency Radiation - Concepts
Class - 9th Aus Edu Subjects
 
 
Concept Explanation
 

Ultraviolet Rays

The ultraviolet rays were discovered by Ritter in 1801. The frequency range of ultraviolet rays is 8x 1014 Hz to 5 x 101 Hz. The ultraviolet rays are produced by sun, special lamps and very hot bodies.

Most of the ultraviolet rays coming from sun are absorbed by the ozone layer in the earth's atmosphere. The ultraviolet rays in large quantity produce harmful effect on human eyes. Ultraviolet light has shorter wavelengths than visible light, with lengths of 10 to 400 nanometers. While invisible to humans, as with infrared light we can see the effects

 
  • Ultraviolet (UV) light is radiation with a higher frequency than violet light ('ultra means 'beyond) Sunlight contains UV light in addition to infrared and visible light.
  • Your body needs some exposure to UV light to produce vitamin D.
  • Although you cannot see UV light. it can tan or burn your skin. High exposure to UV light can cause skin cancers such as melanoma.
  • UV light can also cause cataracts in your eyes.
  • Approved sunglasses and sunscreens can offer us some protection from these rays.
  • The Bureau of Meteorology issues daily UV index forecasts like the one shown to help you take precautions to protect yourself against damage from UV radiation.
  • The ultraviolet lamp usually consists of an electric discharge lamp with material that yields radiations at the desired wavelength. Ultraviolet lamps are usually housed in quartz or special glass that transmits ultraviolet radiation more readily than ordinary glass.
  • Some objects, such as the rocks  fluoresce (glow) when hit by UV light. This is because they absorb the energy from the UV light and emit Visible light. Manufacturers of white paper, teeth whiteners and some laundry powders add fluorescent particles to make these objects appear brighter. UV light is also used to sterilise objects.

    Uses:

    Ultraviolet rays are used

    (i) for checking the mineral samples through the property of ultraviolet rays causing flourescence.

    (ii) in the study of molecular structure and arrangement of electrons in the external shell through ultraviolet absorption spectra.

    (iii) to destroy the bacteria and for sterilizing the surgical instruments.

    (iv) in burglar alarm.

    (v) in the detection of forged documents, finger prints in forensic laboratory.

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    Sample Questions
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    Question : 1

    Out of these who can offer us some protection from ultraviolet rays?

    Right Option : C
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    Question : 2

    The UV  rays are produced by ________________________.

     

    Right Option : D
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    Explanation
    Question : 3

    Who can see the UV light ?

    Right Option : D
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