11. A spaceship approaches a stationary light source at a speed 1.20 × 10 7 m/s.
ID: 1397127 • Letter: 1
Question
11.
A spaceship approaches a stationary light source at a speed 1.20 × 107 m/s. The astronauts perceive the frequency of the light to be 4.39 × 1014 Hz. At what frequency is the source emitting light? (Note: The speed of light is 3.00 × 108 m/s.)
4.05 × 1014 Hz
4.39 × 1014 Hz
4.76 × 1014 Hz
3.89 × 1014 Hz
13.
What is the intensity level of a sound with an intensity of 6.5 x 10-6 W/ m 2?
11 dB
68 dB
34 dB
60 dB
14.
In the diagram, the dot labeled S is moving from left to right. The dot represents a source of sound, and some of the wavefronts are shown.
You are standing to the right of S, meaning that the source of sound is approaching you. How do you perceive the sound in comparison to a person traveling with the source?
You hear the same pitch at the same volume.
You hear a higher pitch.
You hear the same pitch at louder volume.
You hear a lower pitch.
15.
A train is approaching a signal tower at a speed of 40 m/s. The train engineer sounds the 1000-Hz whistle, while a switchman in the tower responds by sounding the 1200-Hz siren. The air is still and the speed of sound is 340m/s
What is the frequency of the train whistle tone that is heard by the switchman?
1000 Hz
340/380 × 1000 Hz
380/340 × 1000 Hz
300/340 × 1000 Hz
340/300 × 1000 Hz
11.
A spaceship approaches a stationary light source at a speed 1.20 × 107 m/s. The astronauts perceive the frequency of the light to be 4.39 × 1014 Hz. At what frequency is the source emitting light? (Note: The speed of light is 3.00 × 108 m/s.)
4.05 × 1014 Hz
4.39 × 1014 Hz
4.76 × 1014 Hz
3.89 × 1014 Hz
Explanation / Answer
12) 4.05 × 1014 Hz
13) 68 dB
souond intensity level, beta = 10*log(I/Io)
= 10*log((6.5*10^-6)/10^-12)
= 68.13 dB
14) You hear the same pitch at louder volume.
15) 340/300 × 1000 Hz
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