Summary

• Wave interference
• Standing waves
• Sound waves

• Sound intensity
• definition of intensity
• point source
• sound level in decibels
Example #a
Example #b

• The Doppler effect
• description

• video
• applet & another applet
• shock waves (ripple tank simulation)
• shock waves video
• acoustic compressor diagrams
Example #1
Example #2
Example #3
Example #4




• Interactive Example Doppler effect



• the Doppler effect for light
• Ripple tank applet
• astronomy
• Stellar motion applet
• police radar
• weather radar
• Doppler radar image of tornado
Example #5
Example #6
Example #7
Example #8




Analysis of radar returns for the May 31, 2013 tornado near El Reno, OK. This image depicts the locations of rain drops based on the time delay between when the radar waves were emitted and when they returned to the antenna. Credit: Steve Horstmeyer

This second image, taken at about the same time as the previous, indicates the velocity of the rain drops by using the Doppler effect. Red is leftward air movement (away from the radar antenna), green is rightward air movement. The tornado (red triangle) is centered at the boundary between the two. The yellow shape indicates the damage path of the tornado (determined later, after the storm had passed).

PSE10e 16.34a
The average sound intensity 100 m from an exploding firework is 7.00×10⁻² W/m² for 0.200 s. What is the total amount of sound energy produced by the explosion?
A. 0.0140 J
B. 126 kJ
C. 8800 J
D. 1760 J
Answer



















PSE10e 16.34a
The average sound intensity 100 m from an exploding firework is 7.00×10⁻² W/m². What is the sound level in decibels?
A. 10.8 dB
B. 52.0 dB
C. 88.8 dB
D. 108 dB
Answer



















kw4
When you drive your car at a constant speed toward a police car, what happens to the frequency of the radar when it bounces off your car?
A. It is shifted higher.
B. It is shifted lower.
C. It stays the same frequency.
Answer



















PoP5
Consider "listeners" at points A, B, and C in the figure. Which of the following is true?
A. The wave speed is highest at point C.
B. The detected wavelength is largest at point C.
C. The detected frequency is highest at point C.
D. The detected wavelength is largest at point B.
Answer



















klm
What is the frequency you hear when a 500-Hz siren recedes from you at 25.0 m/s? Assume you are standing at rest and that v_sound = 343 m/s.
A. 432 Hz
B. 500 Hz
C. 466 Hz
D. 534 Hz
Answer



















PSE9 17.37
An ambulance moving at 42 m/s sounds its siren whose frequency is 450 Hz. A car is moving in the same direction as the ambulance at 25 m/s. What frequency does a person in the car hear as the ambulance approaches the car from behind? Assume v_sound = 343 m/s.
A. 430 Hz
B. 475 Hz
C. 550 Hz
D. 756 Hz
Answer















Walker4 25.21
Suppose a particular galaxy emits orange light with a frequency of 5.000×10¹⁴ Hz. If the galaxy is receding from Earth with a speed of 3325 km/s, what is the frequency of the light when it reaches Earth?
A. 5.109×10¹⁴ Hz
B. 4.889×10¹⁴ Hz
C. 5.055×10¹⁴ Hz
D. 4.945×10¹⁴ Hz
Answer















Walker5e 25.14a
When an airplane uses microwave communication with a satellite at a frequency of 1.535×10⁹ Hz, the signal received by the satellite is shifted higher by 207 Hz. Is the airplane moving toward or away from the satellite?
A. toward
B. away
Answer















Walker5e 25.14a2
When an airplane uses microwave communication with a satellite at a frequency of 1.535×10⁹ Hz, the signal received by the satellite is shifted higher by 207 Hz. Is the speed of the microwaves detected by the satellite greater than, less than, or equal to c?
A. greater than c
B. less than c
C. equal to c
Answer















Walker5e 25.14b
When an airplane communicates with a satellite at a frequency of 1.535×10⁹ Hz, the signal received by the satellite is shifted higher by 207 Hz. What is the component of the airplane's velocity toward the satellite?
A. 0.0202 m/s
B. 40.5 m/s
C. 318 km/s
D. 2.22×10¹⁵ m/s
Answer



































 



D. 1760 J
Write solution here




















 



B. 108 dB
Write solution here.
























answer

A. It is shifted higher.
The source of the reflected waves is moving toward you, and that produces a Doppler shift to higher frequencies.



















answer

C. The detected frequency is highest at point C
The wave speed is constant, so when the source moves toward the right the crests bunch up in that direction and the detected frequency is higher.



















answer

C. 466 Hz




















answer

B. 475 Hz
















 



D. 4.945×10¹⁴ Hz





















 



A. toward
A component of the airplane's velocity must be toward the satellite because the received frequency is higher than the emitted frequency.




















 



C. equal to c
The speed of light is equal to c, independent of the speed of the source.




















 



B. 40.5 m/s

























 
Idea behind acoustic refrigeration: