Physics problem sheet 1
Infrasound and Ultrasound
JJ Lawton
October 6, 2013
Problem 1
Use the graph axes below to draw one oscillation of a wave. Label
the wavelength and amplitude of the wave.
One oscillation is one
complete wave; no more,
no less.
1
0.5
0
−0.5
−1
Problem 2
In air, sound travels at approximately 340 ms−1 .
A pianist plays a ‘middle C’ note on the piano, it has a frequency
of 261.6 Hz. How long is each wave?
The s−1 is another way of
saying 1s . So the units for
speed are m
s , metres per
second.
You will need to
rearrange the equation:
v = fλ
1
Problem 3
The pianist plays a ‘Top C’ and the sound waves produced have a
wavelength of 0.65 m. Calculate the frequency of this note and compare
it the ‘middle C’.
Problem 4
A scientist measured the wavelength of the ultrasonic sound produced
by a bat using its echo location and the infrasound of a whale call. The
data can be seen below. Do you think the scientist has made accurate
measurements?
Animal observed Wavelength of sound (m)
Bat
85
Whale
0.0068
2
You don’t know what
wavelengths are classed as
ultrasound or infrasound,
only the frequencies. You
need to do a calculation
to answer this question.