Name: ______________________________________________________ Date:__________________________
Assignment
Unit
Example: Intensity of Sound Waves
What is the intensity of the sound waves produced by a trumpet at a distance of 3.2 m when the power output of
the trumpet is 0.20 W? Assume that the sound waves are spherical.
Practice A: Intensity of Sound Waves
1. Calculate the intensity of the sound waves from an electric guitar’s amplifier at a distance of 5.0 m when it
power output is equal to each of the following values:
a. 0.25 W
b. 0.50 W
c. 2.0 W
2. At a maximum level of loudness, the power output of a 75-piece orchestra radiated as sound is 70.0 W. What
is the intensity of these sound waves to a listener who is sitting 25.0 m from the orchestra?
3. If the intensity of a person’s voice is 4.6 × 10−7 W/m2 at a distance of 2.0 m, how much sound power does
that person generate?
4. How much power is radiated as sound from a band whose intensity is 1.6 × 10−3 W/m2 at a distance of 15 m?
5. The power output of a tuba is 0.35 W. At what distance is the sound intensity of the tuba 1.2 × 10−3 W/m2?
Physics
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Mr. Almeida
Each pulse is moving towards the middle at 1 cm/s. What will the medium look at like after 2 seconds?
1.
t=0s
2.
t=2s
3.
t=0s
t=2s
4.
t=2s
Physics
t=0s
t=0s
t=2s
-2-
Mr. Almeida
Power in a Wave
See this link and this link.
Physics
-3-
Mr. Almeida
Doppler Effect
1. You are standing at x = 0 m, listening to a sound that is emitted at frequency
f0. The graph shows the frequency you hear during a four-second interval.
Which of the following describes the sound source?
(A) It moves from left to right and passes you at t = 2 s.
(B) It moves from right to left and passes you at t = 2 s.
(C) It moves toward you but doesn’t reach you. It then reverses direction at
t = 2 s.
(D) It moves away from you until t = 2 s. It then reverses direction and moves
toward you but doesn’t reach you.
Justify your answer:
2. You are standing at x = 0 m, listening to a sound that is emitted at frequency
f0. At t = 0 s, the sound source is at x = 20 m and moving toward you at a
steady 10 m/s. Draw a graph showing the frequency you hear from t = 0 s to
t = 4 s. Only the shape of the graph is important, not the numerical values of f.
3. You are standing at x = 0 m, listening to seven identical sound sources. At t = 0 s, all seven are at x = 343 m
and moving as shown below. The sound from all seven will reach your ear at t = 1 s.
Rank, in order from highest to lowest, the seven frequencies f1 to f7 that you hear at t = 1 s.
Highest
Lowest
Justify your answer:
Physics
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Mr. Almeida