Wobble some waves

A standing (or stationary) wave is a wave that appears to stay in the same place. To make one, find a skipping rope and a friend. Get your friend to hold one end still whilst you spin the other end.

imageTry spinning the rope at different speeds. Can you make these shapes?waveshapes

Tip – It is difficult to change from one shape to another so you might need to stop spinning (or try shaking the rope around) before changing speed.

You can create a standing wave using sound, but you can’t see it… unless you have a Rubens’ tube. This is a metal tube sealed at one end, with a loudspeaker at the other. There is a line of holes along the top. The tube is filled with gas to form a row of tiny flames. When there is no sound the flames are all the same height.

If a long note is played through the speaker it will send vibrations along the Rubens’ tube. These vibrations bounce off the other end of the tube and pass vibrations traveling in the opposite direction. The vibrations combine together so that a series of high and low pressure areas are created and the height of the flames changes to represent the standing wave.