Knowledge of ultraviolet (UV) radiation is coupled with an understanding of the electromagnetic spectrum. Electromagnetic radiation is a wave of energy traveling at the speed of light. Electromagnetic waves can be characterized by the following two features that can be measured:

1. Wavelength is the distance between crests or the successive highest points of a wave.
   Wavelengths in the electromagnetic spectrum range from 108 to 10-16
   meters
   The visible band of electromagnetic radiation is between 400 to 700
   nannometers
   (A nannometer is abbreviated as “nm” and is equal to one billionth of a
   meter or 10-9 meter.)
   Ultraviolet radiation is in the electromagnetic spectrum range of 100 and 400 nm.
   
   
2. Frequency is the number of wave crests that pass a given point per second and is usually expressed as “cycles per second” or Hertz (Hz).
   The frequencies of electromagnetic radiation range from 10 Hz to 1024 Hz
   Ultraviolet radiation has frequencies between 1015 to 1017 Hz.
   
   Looking at the electromagnetic spectrum chart on the next page, you will find UV radiation between visible light and X-rays. In terms of energy, the higher the frequency, the higher the energy; therefore, UV radiation is on the higher energy end of the electromagnetic spectrum.

The Electromagnetic Spectrum

There are three types of UV radiation identified within the 100 to 400 nm range. They are:

UV A - 330-400 nm - causes aging, wrinkling, and loss of elasticity of skin

UV B - 290-330 nm - causes the greatest risk of skin cancer

UV C - 100-290 nm - very destructive to tissues, however most is absorbed by the Earth’s atmosphere before reaching ground level

While sunlight is generally the primary energy source for food production by plants, it is also necessary for the human body to produce vitamin D. However, prolonged and direct exposure to the sun means more exposure to damaging UV radiation. Students need to take responsibility for assessing their UV risk and act accordingly for themselves and others for whom they may be responsible (such as a younger sibling or a child whom they babysit.)

Ultraviolet Radiation Concept Map