Question

which of the following are true about the doppler effect?
select all that apply
a the doppler effect only occurs when the source of the sound waves is moving.
b the doppler effect can occur when the listener is moving and the source of sound is stationary.
c the doppler effect can cause the pitch of a sound to change.
d the doppler effect is a change in the frequency of sound waves.

Explanation:

• Option a: The Doppler effect occurs when there is relative motion between the source of sound waves and the listener. It is not limited to only when the source is moving. So, this option is false.
• Option b: If the listener is moving towards or away from a stationary source, the Doppler effect occurs. For example, a person running towards a speaker playing music will hear a higher - pitched sound (higher frequency) than when standing still. This option is true.
• Option c: Since the Doppler effect changes the frequency of sound waves, and pitch is related to frequency (higher frequency means higher pitch), it can cause the pitch of a sound to change. This option is true.
• Option d: By definition, the Doppler effect is a change in the frequency of sound (or other wave) waves due to the relative motion between the source and the observer. This option is true.

Answer:

B. The Doppler effect can occur when the listener is moving and the source of sound is stationary.
C. The Doppler effect can cause the pitch of a sound to change.
D. The Doppler effect is a change in the frequency of sound waves.