KS3 Science - Electromagnetic Spectrum: Ultra Violet

Johann Ritter discovered ultraviolet light in 1801

While UV rays can be harmful to human health, some beneficial applications are

• Short exposure to UVB (a type of UV radiation) generates vitamin D
• In medicine, UV rays help to kill bacteria and viruses and to sterilise equipment
• Scientists utilise the characteristics of Ultra Violet rays to study structure of atoms.

Effects of UV rays are different for different conditions and locations on the globe. Above diagram helps to ascertain the level of exposure based on various factors. 

More from WHO....

* Skin cancer is the most common form of cancer in the United States

* Ultraviolet (UV) radiation, from the sun and from tanning beds, is classified as a human carcinogen, according to the U.S. Department of Health and Human Services and the World Health Organization (http://www.epa.gov/sunwise/doc/uvradiation.html)

** Fluorescent bulbs typically use 65%-75% less energy than a standard incandescent bulb

source NASA graphic

• There are various spectrum ranges of energy emitted from the sun : visible light,  infrared radiation, and ultraviolet (UV) radiation.
• UV radiation has a shorter wavelength and higher energy than visible light. 
• UV light can have positive and negative effects on human health.
• A good portion of the sun's UV rays are absorbed by the atmosphere's stratospheric ozone layer
• Some animals, birds, butterflies and insects can see UV rays

A number of substances are able to absorb the energy in UV light and immediately convert it into visible light. This effect is called fluorescence. The ink in highlighter pens contains a fluorescent dye that enables the ink to reflect vividly in sunlight and to glow strongly in the dark when a UV lamp is shone on it.

We can use UV and fluorescence to make efficient lighting for offices, workshops and our own homes.

Read morea about UV and fluorescence here....

A UV toothbrush sterilizer

A UV sterilizer utilizes a germicidal fluorescent lamp that produces light at a wavelength of approximately 254 nanometers. As the light penetrates the bacteria, it mutates the DNA (genetic material), preventing growth/multiplication of the organism.

source : http://www.fosterandsmithaquatics.com/PIC/Article.cfm?d=260&category=265&articleid=2212

Some of the common dangers of UV rays on human health, specially due to time spent outdoors

• Skin cancer
• Cataracts
• Suppression of the immune system
• Premature aging of the skin

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