Beats (AP1)
1.
Wave A interferes with Wave B to produce the resultant Wave C. At each interval, add the amplitude of Wave A
to Wave B and create the resultant Wave C
2. Rectangular transverse wave oulses are traveling towardds eachother along a string. The grides shown in the
background are identical, and the pulses vary in height and length. The pulses will meet and interact soon after
they are int he position shown. Rank from greatest to least maximum amplitude of the string at the instant
that the position of the centers of the two pulses coincide. Justufy your ranking.
3. Do interference beats have anything to do with the “beat” of music? Explain.
4. Two adjacent point sources, A and B, are directly in front of an observer and emit identical 1000 Hz tones. At
what closest distance behind source B would source A have to be moved for the observer to hear no sound?
(Assume air temperature is 20oC) (0.172 m)
5. As a person walks in between a pair of loudspeakers that produce tones of the same amplitude and frequency, he
hears a varying sound intensity. Explain.
6. If the frequency of two speakers were lowered, would the points where destructive and constructive interference
occur move further apart or closer together? Explain.
7. An airplane mechanic notices that the sound from a twin-engine aircraft varies rapidly in loudness when both
engines are running. What could be causing this variation from loud to soft?
8. A violinist tunes her instrument by listening to the correct frequency and then adjusting the violen until she no
longer hears any beats. As the violen becomes more in tune, what happens to the beat frequency? Explain.
9. Two tuning forks are hit at the same time. One has a frequency of 630 Hz and a beat frequency of 13 Hz is heard.
What two possible frequencies could the other tuning fork have?
10. A G can either have a frequency of 384 Hz while an F has a frequency of 341.3 Hz. If played together, what beat
frequency will be heard?
11. Two identical point sources are generating waves witht he same frequency and amplitude. The two sources are in
phase with eachother so the two sources generate wave crests at the same instant.
a. The wavelength of the waves is equal to the distance between the two sources. Fill out the table
describing each labeled point as hearing constructive or destructive interference and then explain why.
Constructive
Destructive
Interference
Interference
A
B
C
D
E
b. The distance between the two sources is equal to one and one-half the wavelength (1.5). Fill out the
table describing each labeled point as hearing constructive or destructive interference and then explain
why.
Constructive
Interference
A
B
C
D
E
F
Destructive
Interference