Ultra Violet

 

How they're made

Ultra-Violet light is made by special lamps, for example, on sun beds. It is given off by the Sun in large quantities. We call it "UV" for short.

The photo shows a UV lamp in a chip shop. The lamp gives off UV (which you can't see) as well as violet light (which you can see).

The UV attracts insects, which are electrocuted by high-voltage wires near the lamp - so they won't land on the food and contaminate it.


Uses

Forged banknotes can be detected by looking at them under UV light Uses for UV light include getting a sun tan, detecting forged bank notes in shops, and hardening some types of dental filling.

You also see UV lamps in clubs, where they make your clothes glow. This happens because substances in washing powder "fluoresce" when UV light strikes them - they absorb the UV and then re-radiate the energy at a longer wavelength. Your teeth do the same thing!
The lamps are sometimes called "blacklights" because we can't see the UV coming from them.

When you mark your posessions with a security marker pen, the ink is invisible unless you shine a UV lamp at it.

Ultraviolet rays can be used to kill microbes. Hospitals use UV lamps to sterilise surgical equipment and the air in operating theatres.

Food and drug companies also use UV lamps to sterilise their products.

Suitable doses of Ultraviolet rays cause the body to produce vitamin D, and this is used by doctors to treat vitamin D deficiency and some skin disorders.

Something else to try in a club, with a glass of tonic: UV light makes the quinine in tonic water glow pale blue.

This video clip from YouTube shows it clearly :

Dangers


Large doses of UV can damage the retina in your eyes, so it's important to check that your sunglasses will block UV light.

The cheaper sunglasses tend not to protect you against UV, and this can be really dangerous. When you wear sunglasses the pupils of your eye get bigger, because less light reaches them.

This means that if your sunglasses don't block UV, you'll actually get more ultra-violet light in your eyes than if you didn't wear them, although you won't notice at the time. So before you buy sunglasses, check that they offer UV protection!

Large doses of UV cause sunburn and even skin cancer. Fortunately, the ozone layer in the Earth's atmosphere screens us from most of the UV given off by the Sun. Think of a sun tan as a radiation burn!



Surprised to learn that there are just 4000 tigers left in the wild? Do something about it - Adopt a Tiger with the WWF!