How we get a feel for radio waves

17th January 2003 at 00:00
When students are taught about the electromagnetic spectrum they often have difficulty realising that radio waves, microwaves, infrared, visible light, ultraviolet, X-rays and gamma rays are all the same thing. The only difference is the frequency of the wave.

The first part of the lesson is a fun way to see how different waves have different amounts of energy. Seven students come to the front of the class and take a basketball. They should stand in the order indicated above, from radio waves to gamma rays. The students who are in front start to clap in time, once every three seconds. The person with the radio waves should bounce their ball once every clap; and so on until the person with gamma rays has to bounce their ball seven times every clap (this is pretty fast so a good basketball player may be required).

In the second part, to explain how a microwave works, they sit in rows to represent the atoms in a solid. They are the food in a microwave. Each student is given a blue balloon, which they blow up, tie at the end and hold. The balloons represent the water molecules in food.

The teacher will need a large stereo and some music with a very deep bass. (I use the song music "Mr Boombastic") to represent the microwaves being emitted. The students hold on to the sides of the balloon and they should be able to feel the balloon vibrate as the song is played. This shows that microwaves have the same frequency as the resonant frequency of the water molecules. As the water molecules move they get hot and it is this which cooks the food.

Jonathon Lisseman teaches science at Quintin Kynaston School, St John's Wood, London borough of Westminster

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