Cambridge Science Centre


My Favourite Exhibit: Bell Jar

Written on 20 May 2013 in Blog

Other than for breathing, why do we need air? Most of the time we don’t really notice it, but if it wasn’t there, you definitely would. My favourite exhibit, the bell jar, gives a really clear, simple example of another reason air is important - for hearing.

The set-up is simple, an alarm clock inside a perspex jar. But when you turn on a pump and remove the air from the jar, things really get interesting. The sound of the bell ringing stops, even though you can still see it moving!

Normally, the bell causes a vibration in the air, which travels to your ear and produces sound. If there isn’t any air, there is nothing for the vibration to travel through, so it can’t reach your ear, and the sound stops. So rather than taking the air for granted, remember that without it, the world would be a much quieter place!

Written by Ginny Smith