14.3 Doppler Effect and Sonic Booms

What is the Doppler effect?

• A change in the observed pitch of a sound due to relative motion

• A phenomenon where sound waves are absorbed by materials

• A process of sound amplification

• A method of sound wave reflection

Which of the following is an example of the Doppler effect?

• The sound of a siren changing pitch as it passes by

• The echo of a sound in a canyon

• The amplification of sound in a concert hall

• The reflection of sound waves off a wall

How does the frequency of sound change for an observer moving toward the source?

• It increases, resulting in a higher pitch

• It decreases, resulting in a lower pitch

• It remains the same

• It fluctuates randomly

What happens to the wavelength of sound waves when the source is moving away from the observer?

• The wavelength becomes longer

• The wavelength becomes shorter

• The wavelength remains unchanged

• The wavelength fluctuates randomly

If you are standing on the sidewalk facing the street and an ambulance drives by with its siren blaring, at what point will the frequency that you observe most closely match the actual frequency of the siren?

• when it is coming toward you

• when it is going away from you

• when it is in front of you

• when it is behind you

What happens to the frequency of sound as a jet airplane approaches the speed of sound?

• The frequency decreases.

• The frequency remains constant.

• The frequency increases.

• The frequency becomes zero.

What is a sonic boom?

• A sound created by a slow-moving object.

• A sound created by an object moving faster than sound.

• A sound created by an object moving at the speed of light.

• A sound created by an object moving slower than sound.

What is the effect on the observer when a source moves at the speed of sound?

• The observer hears no sound.

• The observer hears a continuous sound.

• The observer hears all sounds at the same instant.

• The observer hears a decreasing frequency.

What is the formula used to calculate the observed frequency when the source is moving away from the observer?

What is the speed of sound used in the worked example?

• 150 m/s

• 340 m/s

• 170 m/s

• 136 m/s