Doppler Effect

The pitch of a sound wave relates to the wave's _________________.

• Amplitude

• Frequency

• Wavelength

• Period

What is the Doppler Effect?

• A change in frequency due to the relative motion of a wave source and an observer

• When a wave overlaps with another wave

• When a wave bounces off of another object

• When a wave bends due to traveling through a different medium

An ambulance is driving towards you as you stand on the sidewalk. What happens to the pitch of the siren as it comes towards you?

• It increases

• It decreases

You are driving in a car and honk the horn at a person standing in the street. As you approach the person, what happens to the pitch of the horn according to you in the car?

• It increases

• It decreases

• It stays the same because you are in the car moving with the sound.

You stand on the sidewalk next to the street. A fire truck is away from you. The frequency of the siren on the fire truck is 600 Hz.

What should you hear?

• Frequency higher than 600 Hz

• Frequency lower than 600 Hz

• Exactly 600 Hz

• No sound, silence.

A car moves at 20 m/s away from a whistle. The whistle is stationary. The whistle makes a sound with a frequency of 500 Hz. The speed of sound in air is 330 m/s.

What is the frequency observed by the driver of the car?

• 530 Hz

• 470 Hz

• 520 Hz

A car moves at 20 m/s towards a whistle. The whistle is stationary. The whistle makes a sound with a frequency of 500 Hz. The speed of sound in air is 330 m/s.

What is the frequency observed by the driver of the car?

• 530 Hz

• 470 Hz

• 480 Hz

An ambulance is moving towards a stationary listener at a constant speed of 30 m∙s-1 . The siren of the ambulance emits sound waves having a wavelength of 0,28 m. Take the speed of sound in air as 340 m∙s-1

Calculate the frequency of the sound waves emitted by the siren as heard by the ambulance driver.

An ambulance is moving towards a stationary listener at a constant speed of 30 m∙s-1 . The siren of the ambulance emits sound waves having a wavelength of 0,28 m. Take the speed of sound in air as 340 m∙s-1 .

Calculate the frequency of the sound waves emitted by the siren as heard by the listener.

Choose the correct answer.