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AP Physics 2: Algebra-Based Practice Quiz: The Doppler Effect

Written by AP Content Team, Verified for 2026 AP Exams, Last updated: May 2026

Test your understanding with short quizzes. This quiz has 10 questions to check your progress.

Question 1 of 10

The Doppler effect is a phenomenon that describes the change in a wave's properties based on what factor?

All Questions (10)

The Doppler effect is a phenomenon that describes the change in a wave's properties based on what factor?

A) The amplitude of the wave source.

B) The relative motion between the wave source and the observer.

C) The medium through which the wave travels.

D) The initial phase of the wave.

Correct Answer: B

Based on the provided content, the Doppler effect describes wave properties based on the 'relative motion between the source of the wave and the observer of the wave.'

According to the Doppler effect, what is the relationship between the observed frequency and the rest frequency when a wave source is moving toward an observer?

A) The observed frequency is less than the rest frequency.

B) The observed frequency is equal to the rest frequency.

C) The observed frequency is greater than the rest frequency.

D) The observed frequency is unrelated to the rest frequency.

Correct Answer: C

The content explicitly states, 'For a wave source moving toward an observer, the observed frequency is greater than the rest frequency.'

A student observes a wave source that is moving directly away from them. How will the frequency they observe compare to the frequency emitted by the source at rest?

A) The observed frequency will be higher.

B) The observed frequency will be lower.

C) The observed frequency will be the same.

D) The observed frequency will fluctuate randomly.

Correct Answer: B

The provided text states, 'For a wave source moving away from an observer, the observed frequency is less than the rest frequency.'

An ambulance with its siren on is traveling at a constant speed toward a stationary observer. Which of the following correctly describes the frequency of the siren's sound as perceived by the observer?

A) It is lower than the siren's rest frequency.

B) It is higher than the siren's rest frequency.

C) It is exactly the same as the siren's rest frequency.

D) It decreases as the ambulance gets closer.

Correct Answer: B

Since the ambulance (the wave source) is moving toward the observer, the observed frequency will be greater than the rest frequency.

A train blowing its horn passes a stationary observer at a platform and continues to move away. What happens to the observed frequency of the horn as the train moves away from the observer?

A) The observed frequency becomes greater than the horn's rest frequency.

B) The observed frequency becomes less than the horn's rest frequency.

C) The observed frequency remains equal to the horn's rest frequency.

D) The observed frequency becomes zero.

Correct Answer: B

The content specifies that for a wave source moving away from an observer, the observed frequency is less than the rest frequency.

An astronomer measures the frequency of a distant star's light and finds it to be lower than the known rest frequency of the elements in that star. What can be inferred about the motion of the star relative to the observer?

A) The star is moving toward the observer.

B) The star is stationary relative to the observer.

C) The star is moving away from the observer.

D) The star is orbiting the observer.

Correct Answer: C

A lower observed frequency compared to the rest frequency indicates that the wave source (the star) is moving away from the observer, as stated in the provided content. This phenomenon is known as redshift in astronomy.

If the observed frequency of a wave is measured to be significantly greater than its rest frequency, what does this imply about the relative velocity between the source and the observer?

A) The source and observer are moving away from each other.

B) The source and observer are stationary relative to each other.

C) The source and observer are moving toward each other.

D) There is no relative velocity between the source and observer.

Correct Answer: C

The content states that an observed frequency greater than the rest frequency occurs when the wave source is moving toward the observer.

The Doppler effect establishes a relationship between which of the following sets of variables?

A) Wave amplitude, wavelength, and medium density.

B) Rest frequency, observed frequency, and relative velocity.

C) Wave speed, source temperature, and observer distance.

D) Phase angle, wave intensity, and source size.

Correct Answer: B

The text explicitly states that the Doppler effect 'describes the relationship between the rest frequency of a wave source, the observed frequency of the source, and the relative velocity of the source and the observer.'

A car sounding its horn drives at a constant speed, passing a person standing on the sidewalk. Which statement best describes the frequency the person hears?

A) The frequency is consistently lower than the horn's rest frequency.

B) The frequency is consistently higher than the horn's rest frequency.

C) The frequency is higher as the car approaches and then becomes lower as it moves away.

D) The frequency is lower as the car approaches and then becomes higher as it moves away.

Correct Answer: C

This scenario combines both principles from the content. As the car (source) moves toward the observer, the observed frequency is greater than the rest frequency. After it passes and moves away, the observed frequency becomes less than the rest frequency.

The fundamental principle described by the Doppler effect is that the perceived properties of a wave are dependent on the...

A) absolute motion of the source.

B) absolute motion of the observer.

C) relative motion between the source and the observer.

D) physical medium separating the source and the observer.

Correct Answer: C

The first sentence of the provided content states that the properties of a wave are described 'based on the relative motion between the source of the wave and the observer of the wave.'