| Term | Definition |
|---|
| Radio Waves | They are used for radio broadcasts, amateur radio, television, and mobile phones. Different parts of the radio spectrum have been allocated to the various services. Radio waves have a much longer wavelength that light waves. The longest waves are several kilometers in length. The shortest ones are only millimeters long. |
| Microwaves | Microwaves have such a short wavelength that they are very easily absorbed by water. This is why they are used in microwave ovens. What happens is that when the water in your TV dinner absorbs the microwaves, the energy of the microwaves is converted into heat: it makes the water molecules vibrate faster. Some people are frightened that the radio waves coming out of their mobile phones are short enough to cook their brains. |
| Infra Red | These radio/light waves have a very short wavelength; their wavelength is longer than visible light. Infra-red can be detected by special infra-red film. If the police or MI5 shine an infra-red light on you they will be able to take a picture of you using infra-red film: you will not know that they have taken your photo. |
| The Visible Spectrum | Richard Of York Gave Battle In Vain. = Red, Orange, Yellow, Green, Blue, Indigo, and Violet. are the colours of the visible spectrum. We cannot see Infra-red, but we can feel it warm our skin when we sit in the sun. Infra-red has a longer wavelength (less energy) than Red light. We cannot see Ultra-violet light, but we feel our skin has been burnt by the sun if we were in the sun too long yesterday. It is the Ultra-violet which is thought to cause skin cancer. UV light has a shorter wavelength (more energy) than visible light. |
| Ultra Violet | These waves have very high energy and very short wave lengths; shorter than visible light. Some animals like honey bees can see ultra-violet light. Some plants have white flowers, at least you think that they are all white, but they may appear to be different colours to a honey bee because of the amounts of ultra-violet light which they reflect. |
| X-Rays | X-Rays have so much energy and such a short wavelength that they can go right through you. However, they cannot get through bone as easily as they can get through muscle. This is because your bones contain so much Calcium. |
| Gamma Rays | They have very high energy and will even go through metals. So they can be used for finding tiny cracks in metals. You cannot see the hairline cracks in an aeroplane wing with the naked eye. How would you like the wings to fall off the plane on your summer holiday flight to Neasden or wherever it is that you go. If the plane has been thoroughly checked you should be safe. Some radioactive materials produce gamma rays. Gamma rays and X-Rays can cause cancer, but gamma rays can also be used to destroy cancer cells: this is radio-therapy. |
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