The document describes interference patterns created by two sound sources with the same frequency emitting sound waves into a room. Constructive interference occurs at points where wave crests and troughs overlap, specifically at points B, C, and D. Destructive interference only occurs at point C, where a crest and trough meet. If the frequencies of the two sources are changed, with one increasing greatly and the other decreasing greatly, the sound would be heard as two distinct tones rather than a single tone with varying intensity due to the large difference between the frequencies.

1. Physics 101 Learning Object 6
Beats
Two objects are placed side by side such that the sound waves they emit radiate through the
room with the same frequency. An interference pattern is created and is represented by the
image below. The thick lines represent wave crests and the thin lines represent wave troughs.
Use the image below to answer the following questions.
1. At which point(s) would constructive interference occur between the two objects?
a) B, C, and D
b) B and D
c) A only
d) All points
2. What about destructive interference?
a) B, C, and D
b) B and D
c) A only
d) All points
3. What would happen to the sound hear if the frequency of O2 is greatly increased and
the frequency of O1 is greatly decreased? Explain.

2. Physics 101 Learning Object 6
Interference & Beats
Two objects are placed side by side such that the sound waves they emit radiate through the
room with the same frequency. An interference pattern is created and is represented by the
image below. The thick lines represent wave crests and the thin lines represent wave troughs.
Use the image below to answer the following questions.
1. At which point(s) would constructive interference occur between the two objects?
a) A, B, and D
b) B and D
c) A only
d) C only
Answer: ​a) is the correct answer. Since the thick lines represent wave crests, when two wave
crests meet, constructive interference occurs. Since thin lines represent the troughs,
constructive interference also occurs when a trough meets a trough. Therefore A, B, and D
are the correct points.
2. What about destructive interference?
a) B, C, and D
b) B and D
c) A only
d) C only
Answer: ​d) is the correct answer. Destructive interference occurs when a crest meets a
trough and the resulting wave is zero, therefore C is the only correct point.
3. What would happen to the sound hear if the frequency of O2 is greatly increased and
the frequency of O1 is greatly decreased? Explain.
Answer: ​When two waves are heard that have different frequencies, increasing and
decreasing amplitudes as a function of time are heard called beats. The amplitude variation is
proportional to the frequency difference. Therefore, when O2 frequency becomes very large
and O1 becomes very small, the difference between the two frequencies will be very large,
leading the two waves to be heard as two distinct tones rather than one with varying intensity.