Uses of Electromagnetic Waves
Each of the waves has different properties. Because of this they are useful for different things.
The most important use is communication. Radio waves can carry signals from one place to another. They are sent out by a transmitter and picked up by a receiver. We saw on the previous page how they produce an alternating voltage in an aerial.
Stars and other objects in the cosmos emit radio waves. Radio astronomy is a very useful tool.
Microwaves are also used for communication. They can pass through the atmosphere easily so are used to send signals to and from satellites. Mobile phone networks use microwaves.
Water molecules absorb microwaves of a certain frequency and so gain energy. This is why things containing water get hot in a microwave oven.
Infra red is heat radiation so has a lot of uses.
Infra red is used to send signals down optical fibres. The signal bounces around inside the glass fibre till it comes out the other end.
Our eyes are sensitive to this part of the electromagnetic spectrum, this is how we see.
Signals can also be sent down optical fibres using visible light.
Ultra violet gives us a sun tan.
Special chemicals absorb UV then emit visible light. You can write your postcode on something with a special pen then this will be invisible except under UV light.
These pass through soft tissues easily (skin, flesh) but not through bone. We can therefore use them to take shadow pictures of bones.
Useful also for finding out if there is a gun in your luggage at the airport.
Gamma rays have a lot of energy and kill cells. They can there fore be used to sterilize things like surgical instruments (scalpels, syringes etc).
In radiotherapy they are used to kills cancer cells.
If you expose food to gamma rays its shelf life is extended greatly.