Question

exam lesson name: light and sound
exam number: 700699rr
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question 3 of 20 :
select the best answer for the question.

1. the change in pitch of a trains horn as it passes while youre standing still can be explained by

○ a. resonance.
○ b. sympathetic vibration.
○ c. the doppler effect.
○ d. ultrasonic vibrations.
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Explanation:

• Option A: Resonance is when an object vibrates at its natural frequency due to external vibrations, not related to pitch change with motion.
• Option B: Sympathetic vibration is one object vibrating due to another's vibration, not about pitch change from moving source.
• Option C: The Doppler effect explains the change in frequency (and thus pitch) of a wave when the source or observer is in motion. A train's horn pitch change as it passes a stationary observer is a classic Doppler effect example.
• Option D: Ultrasonic vibrations are frequencies above human hearing, not related to this pitch - change phenomenon.

Answer:

C. the Doppler effect.