Q1. When a source of sound moves towards an observer, what happens to the frequency of the sound heard?
a) It increases
b) It decreases
c) It remains constant
d) It depends on the amplitude of the sound
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Correct Answer: a) It increases
Explanation: The Doppler Effect causes an increase in the frequency of sound waves when the source moves towards the observer, resulting in a higher perceived pitch.
Q2. What term describes the phenomenon where the frequency of sound waves changes due to relative motion between the source and the observer?
a) Echo
b) Doppler Effect
c) Refraction
d) Interference
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Correct Answer: b) Doppler Effect
Explanation: The Doppler Effect is the change in frequency of sound waves observed when the source or observer is in motion relative to each other, leading to a perceived change in pitch.
Q3. If a sound source moves away from an observer, what happens to the frequency of the sound heard?
a) It increases
b) It decreases
c) It remains constant
d) It depends on the medium of propagation
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Correct Answer: b) It decreases
Explanation: When a sound source moves away from an observer, the frequency of the sound waves decreases due to the Doppler Effect, resulting in a lower perceived pitch.
Q4. What is the term for the apparent change in pitch of sound caused by the relative motion between the source and the observer?
a) Resonance
b) Echo
c) Doppler Effect
d) Refraction
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Correct Answer: c) Doppler Effect
Explanation: The Doppler Effect causes the apparent change in pitch of sound due to the relative motion between the source and the observer, whether approaching or receding.
Q5. Which factor does NOT affect the Doppler Effect?
a) Speed of sound in the medium
b) Speed of the observer
c) Speed of the source
d) Wavelength of the sound waves
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Correct Answer: a) Speed of sound in the medium
Explanation: The Doppler Effect is influenced by the speeds of the observer and the source, as well as the frequency of the sound waves, but not the speed of sound in the medium of propagation.
Q6. What happens to the perceived frequency of sound waves when the observer moves towards a stationary sound source?
a) It increases
b) It decreases
c) It remains constant
d) It depends on the distance between the source and observer
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Correct Answer: a) It increases
Explanation: When the observer moves towards a stationary sound source, the perceived frequency of the sound waves increases due to the Doppler Effect, resulting in a higher pitch.
Q7. Which of the following is NOT an application of the Doppler Effect?
a) Police radar speed guns
b) Doppler weather radar
c) Sonar systems
d) Echo sounding
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Correct Answer: d) Echo sounding
Explanation: Echo sounding is not directly related to the Doppler Effect. It is a method used to determine the depth of water by measuring the time taken for sound waves to travel to the seabed and back.
Q8. What is the minimum distance required between a source of sound and a reflecting surface for an echo to be heard?
a) 10 meters
b) 17 meters
c) 20 meters
d) 34 meters
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Correct Answer: b) 17 meters
Explanation: For an echo to be heard, the minimum distance between the source of sound and a reflecting surface must be approximately 17 meters to allow for the reflection of sound waves with a discernible delay.
Q9. Which of the following materials is a good reflector of sound waves?
a) Concrete
b) Carpet
c) Foam
d) Fabric
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Correct Answer: a) Concrete
Explanation: Concrete is a good reflector of sound waves due to its hard and smooth surface, which allows for efficient reflection of sound, leading to the formation of echoes.
Q10. What term describes the repetition of a sound caused by reflection of sound waves from a surface back to the listener?
a) Resonance
b) Echo
c) Refraction
d) Absorption
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Correct Answer: b) Echo
Explanation: An echo is the repetition of a sound caused by the reflection of sound waves from a surface back to the listener, occurring when the reflected sound arrives with a discernible delay after the original sound.