Ultraviolet energy**

As you saw in the hot cars investigation, solar energy travels from the Sun to the surface of the Earth mainly as visible light, infrared and some ultraviolet (UV).

Visible light, infrared and UV are all forms of electromagnetic wave energy. (These were introduced in the Light module.)

UV energy is absorbed by the atmosphere of the Earth. However, the small amount that does get through from the Sun is very powerful and causes sunburn and skin cancer.

UV energy also can make certain materials glow. It is sometimes used in night clubs or on the stage in a theatre. Certain invisible inks can glow under UV light.

The invisible number on a $20 note can be seen under UV radiation (blue picture).

1. How could invisible inks that glow under UV be used to help detect forged bank notes?
2. Can UV energy be seen by the eye?
3. Why should you avoid excessive exposure to UV energy?
4. What is the range of numbers on the UV scale usually broadcast each day with the weather?

Student section