School Science Experiment - Demonstrating the properties of waves on an Oscilloscope

This is a standard demonstration used in many schools and colleges to demonstrate the basic principles of waves.

Setting Up

A signal generator is connected to an oscilloscope & a loudspeaker. Some signal generators have two outputs:

• one marked with a low value impedance e.g. 8 Ω
• the other marked with a high value e.g 600 Ω.

In this case the high impedence output goes to the osciiloscope, the low to the speaker. If there is only one output connection stackable 4mm plugs[?] are used to connect both devices to the signal generator.

The oscilloscope is adjusted so that there is a clear sine wave trace that extend for about half the screen and has two or three clear waves visible when the signal generator is set at a medium frequency and mid volume.

Demonstrating the Amplitude and Frequency

The advantage of setting the demonstration up in this manner over the more traditional plugging a microphone into the input of the scope, is that the signal generator produces perfect sine waves which keeps everything nice and straightforward.

• By changing the frequency of the signal generator the effect can be both seen on the 'scope and heard on the loud speaker.With a higher frquency showing more complete waves on the screen and a higher pitch of the sound.
• By changine the attenuation (volume)of the signal generator the amplitude of the waveform on the scope can be seen to change & the loudness of the speaker sound changes.

See Also Demonstrating properties of waves with a ripple tank