What is the Doppler effect in the context of sound waves?
A
Change in speed of sound due to medium
B
Change in amplitude of sound near a source
C
Echo formation from hard surfaces
D
Apparent change in frequency due to relative motion between source and observer
Correct Answer: Option D — Apparent change in frequency due to relative motion between source and observer
Explanation:
The Doppler effect describes the apparent change in frequency of sound or light when the source and observer are in relative motion with frequency increasing as they approach and decreasing as they move apart.