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## Chapter 9 Quiz:

1. If a boy is running toward a source of sound of frequency f, will the boy hear a sound of frequency higher, lower or equal than f?

("higher", "lower", "equal")

2. If a boy is running away from source of sound of frequency f, will the boy hear a sound of frequency higher, lower or equal than f?

("higher", "lower", "equal")

3. A woman sees a flash of lightning 1865 m away from her. How long does the sound take to reach her ears?

s

4. By blowing harder into a flute, you ...

a. increase the frequency.
b. decrease the pitch.
c. increase the amplitude.
d. decrease the volume.

(e.g. "a")

5. Can passengers who travel faster than sound speed (Mach 1) hear a sound that is produced inside the airplane?

("yes", "no")

6. Can sound travel through the universe?

("yes", "no")

7. If two waves with frequency ratios of 5:6 reach the ear at the same time, is it considered as noise?

("yes", "no")

8. What is the lowest value in hertz of an ultrasonic wave?

Hz