Waves

Question 1

Give two examples of longitudinal waves.

Answer 1

Sound waves, seismic P waves

Question 2

Give two examples of transverse waves.

Answer 2

Waves on a water surface, electromagnetic waves

Question 3

How do the particles move in longitudinal and transverse waves?

Answer 3

Longitudinal - the particles in the material the sound is travelling through move back and forth along the same direction that the sound is travelling.
Transverse - the particles of water move in a direction at right angles to the direction the wave is travelling.

Question 4

How can the speed of sound in air be calculated using an echo?

Answer 4

1) Measure the distance from the source of the sound to the reflecting surface.
2) Measure the time interval, with a stopwatch, between the original sound being produced and the echo being heard.
3) Use speed = distance / time to calculate the speed of sound in air.

Repeating the experiment a number of times over a range of distances will allow you to obtain accurate and precise rresults.

Question 5

How can the speed of sound in air be measured using two microphones and an oscilloscope?

Answer 5

1) Set up the microphones one in front of the other at different distances in a straight line from a loudspeaker.
2) Set the frequency of the sound from the loudspeaker to a known, audible value.
3) Display the two waveforms on the oscilloscope. Measure the distance between the microphones.
4) Move the microphones apart so that the waveforms move apart by 1 wavelength.
5) Calculate the speed of sound using the equation: wave speed = frequency x wavelength

Question 6

How can the speed of ripples on water surfaces be calculated using a ripple tank?

Answer 6

1) Fill tank with water and place a paddle that can be driven up and down to create regular rhythms. Position a strobe lamp above the tank so it shines down onto the surface.
2) Drive the paddle at a known, steady frequency.
3) Switch on the strobe and vary its flash frequency until the moving ripples appear stationary.
4) With the waves frozen, measure the wavelength. To reduce error, measure across several wavelengths and find an average.
5) Note the strobe frequency in hertz.
6) Use the equation wave speed = frequency x wavelength.

Question 7

What is the average human audible range?

Answer 7

20 Hz to 20,000 Hz

Question 8

What is ultrasound in terms of the human audible range?

Answer 8

Ultrasound are frequencies too high for humans to hear (sound waves with frequencies above 20,000 Hz).

Question 9

What is infrasound in terms of the human audible range?

Answer 9

Infrasound are frequencies too low for humans to hear (sound waves with frequencies below 20 Hz)