Experiments with waves

Question 1

Measure speed of sound

Answer 1

Attach signal generator to speaker, you can generate sounds with specific frequency. Use two microscopes and an oscilloscope to find the wavelength of the sound waves generated

Question 2

Measure speed of sound

PRACTICAL

Answer 2

1) set up oscilloscope so the detected waves at each microphone are shown as separate waves
2) First start with 2 microphones next to speaker, then move one away until the two waves are aligned on display, but have moved exactly one wave length apart

3) measure distance between microphone to find one wavelength
4) use v=f lambda
frequency is what the signal generator is set at
5) speed of sound in air is around 330 m/s so check results

Question 3

Measuring speed of water ripples using a ripple tank
PRACTICAL

Answer 3

1) attach signal generator to dipper of ripple tank to produce water waves with set frequency
2) Dim lights and turn off lamp and you should see wave crests as shadows on the screen below the tank
3) You can freeze waves but taking picture or and measure the distance between the lines that are 10 wavelengths apart, then divide distance by 10 to find average wave length
4) good method for moving waves or small wavelengths
5) v= f x lambda
6) measure wavelength w/o disturbing the waves

Question 4

Describe how the frequency of the water waves in the ripple tank can be measured.

Answer 4

You need to count how many waves pass a point in one second.

That is best done by counting the number of waves that pass a point in a set time and finding out how many would have passed the point in one second.

If you count how many pass a point in a minute and divide the answer by 60 - this will reduce errors compared to picking a small time interval.

You would then need to repeat your measurement a couple of times and find an average.

Question 5

Wave equation for waves on string PRACTICAL

Answer 5

1) set up equipment, turn on signal generator and vibration transducer, spring will then vibrate
2) Adjust the frequency of signal generator until there’s a clear wave on string, frequency depends on length of string between the pulley, and transducer and masses you’ve used

3) measure wavelength of waves, best way to do this accurately is to measure as many wavelengths as you can, divide by two to get mean and double the mean to get full wavelength

4) V = F x lambda

Frequency is whatever signal generator is set to