Physics-Wave speed

What is the wave speed?

It is the speed at which energy is being transferred.

How to measure the speed of a sound wave?

You can generate a sound wave with a specific frequency by attaching a signal generator to a speaker. This sound wave can then be detected by microphones, which convert it to a trace in an oscilloscope.

Equipment- Measuring the speed of a sound wave

* Signal generator
* Speaker
* 2 Microphones

Method-Measuring the speed of a sound wave

1. Set up your equipment with both microphones next to the speaker. The detected wave at each microphone can be seen as a separate wave on the oscilloscope.
2. Slowly move one microphone away from the speaker. Its wave will shift sideways on the oscilloscope. Keep moving it until the two waves on the oscilloscope are aligned once more. At this point the microphones will be exactly one wavelength apart, so measure the distance between them.
3. Then use the formula, the speed of sound is around 330 m/s, so check results match up.

Equipment- measuring the speed of water ripples

* Strobe light
* Screen
* Metre ruler
* Water
* Signal generator
* Dipper
* Ripple tank

Method- measuring the speed of water ripples

1. Fill ripple tank with water to a depth of around 5mm.
2. Connect dipper to signal generator and set it off at a known frequency
3. Dim lights and turn on the strobe light, see a wave pattern made by shadows of wave crests on screen below tank
4. Increase frequency of strobe light until the wave pattern on screen appears to ‘freeze’ and stop moving.
5. Distance between each shadow line is equal to one wavelength.
6. Measure the distance between shadow lines that are 10 wavelengths apart using a metre ruler, then divide this distance by 10 to find the average wavelength.

Observing a wave on a string- Equipment needed

* Vibration transducer
* Signal generator
* Bench
* String
* Pulley
* Masses

What is a vibration transducer?

A vibration transducer will convert an electrical signal from a signal generator into vibrations. When it’s attached to a taut string, waves are formed on the string.

Observing a wave on a string-method

Adjust the frequency of the signal generator until there’s a clear wave on the string. The frequency you need will depend on the length of string between the pulley and the transducer, and the masses you’ve used.

You need to measure the wavelength of these waves. The best way to do this accurately is to measure the length of four or five wavelength in one go, then divide to get the average half-wavelength.

You can then double this wavelength to get the full wavelength.

Then use formula