Measuring Waves Flashcards
How can you generate sounds with a specific frequency?
By attaching a signal generator to a speaker.
How can you use two microphones and oscilloscope to find the wavelength of the sound waves generated?
1) Set up the oscilloscope so the detected waves at each mic are shown as separate waves.
2) Start with both mics next to the speaker, then slowly move one away until the two waves are aligned on the display, but have moved exactly one wavelength apart.
3) Measure the distance between the mics to find one wavelength.
4) Then use the formula ‘v = fλ’ to find the speed of the sound waves passing through the air - the frequency is whatever you set the signal generator at the start.
Describe the water ripples and strobe light practical.
1) Using a signal generator attached to the dipper of a ripple tank, you can create water waves at a set freq.
2) Dim the lights and turn on the strobe light - you’ll see a wave pattern made by the shows of the wave crests on the screen below the tank.
3) Alter the frequency of the strobe light until the wave pattern on the screen appears frozen. This happens when the freq. of the waves and strobe light are equal - the waves appear not to move because they are being lit at the same point in their cycle each time.
4) The distance between each shadow line is equal to one wavelength. Measure the distance between lines that are 10 wavelengths apart, then find the average wavelength.
5) Use ‘v = fλ’ to calculate the speed of the waves.
