If a source of sound waves is rapidly approaching a person, the sound heard by the person appears to have
a. a period higher than the original period.
b. a pitch lower than the original pitch.
c. an amplitude lower than the original amplitude.
d. a frequency higher than the original frequenc

Correct answer choice is:

D. A frequency higher than the original frequency.

Explanation:

This is a true case of Doppler's effect. The Doppler effect can be defined as the effect originated by a traveling source of waves in which there is a visible higher variation in pulse for observers towards what the source is progressing and a visible descending shift in rate for observers from what the source is dropping.

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