4Wave-4

Outcomes

• Pupils can talk about pitch and loundness in terms of frequency and wavelength
• Pupils can take values from oscilloscope readouts

Specification References

• 3.29 understand how an oscilloscope and microphone can be used to display a soundwave
• 3.30 use an oscilloscope to determine the frequency of a sound wave
• 3.31 appreciate that the pitch of a sound depends on the frequency of vibration of the source
• 3.32 appreciate that the loudness of a sound depends on the amplitude of vibration.

Starter

Using the speaker and sig gen change the pitch and loudness. Try to get these terms out of pupils. Also have them observe the display on the oscilloscope and make the link between the two. Finally link to wavelength and the wave speed equation.

Main Body of Lesson

Have pupils draw a standard wave (i.e. a sine wave) and then have them draw 4 varitions on it. High pitch and loud, low pitch and loud, high pitch and quiet and low pitch and quiet. Ensure that they link to amplitude and frequency. Have them do some calculations with the wave speed equation and different frequencies (could use 20 and 20,000Hz) to find the wavelength in air. Could also lonk in here to diffraction of soundwaves through doorways (as the gap size is similar). Next talk about the various settings on an oscilloscope. There is a virtual version here. Link it to being just a graph and they should find it easier to take readings.

Plenary

Draw a wave on the board and ask pupils to make the noise which it represents.

Homework

132-133, also some of the questions from 136-137 in textbook