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# Sound

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1.
Sound can travel long distances through water whereas light only penetrates a short distance.
1. True
2. False
2.
Telephones use electromagnets to change                                .
1. electric currents to light waves
2. electric currents to sound waves
3. magnetism to light waves
4. magnetism to sound waves
3.
A mechanical wave requires a medium through which to propagate and transfer its energy.
1. True
2. False
4.
Sound waves transfer their energy parallel to their movement of compressions and rarefactions. What kind of a wave is a sound wave?
1. transverse
3. electromagnetic
4. longitudinal
5.
The number of sound waves per unit time is called its frequency.
6.
What is the frequency range of human hearing?
1. 20 hertz to 20 kilohertz
2. 2 hertz to 20 hertz
3. 20 hertz to 200 hertz
4. 2 hertz to 200 hertz
7.
Sound waves with a frequency above 20,000 Hz are referred to as
1. infrasonic waves.
2. ultrasonic waves.
3. sonic booms.
4. doppler waves.
8.
Explain the Doppler Effect. Include a real-world example in your explanation.
• The Doppler Effect is the change in frequency of a wave for an observer moving relative to its source. Possible example: The difference in the pitch you perceive you hear as an ambulance with sirens blaring approaches you, passes you, and moves away from you, is an example of the Doppler effect in real life.
9.
When a sound source approaches an observer, the
1. pitch become lower.
2. pitch becomes higher.
3. light becomes bluer.
4. light becomes redder.
10.
The following equation approximates the speed of sound:

$v=[331.4+(0.6)("T in ºC")]m/s$

As shown, temperature is one of the factors that affects the speed of sound. What is the speed of a sound wave in air with an average temperature of 20ºC?
1. 343 meters per second
2. 343 meters per hour
3. 300 million meters per second
4. 300 million meters per hour
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