EMS and Doppler Effect

Doppler Effect

​Doppler Effect

​The apparent change in frequency due to the relative motion of the source (or receiver) is called the Doppler effect.

​

​As a result of the apparent change in frequency, the pitch of the sound produced is impacted.

​

​Frequency is same at A and B

​The frequency of the wave created by the bug has not changed, but because the bug is moving it looks different...

​Shorter wavelength=

higher frequency

​Longer wavelength=

​Lower frequency

​The pitch of the siren has not changed, but what the person hears has changed frequency.

​Pitch and Frequency

Therefore, as the police car approaches the boy, the frequency of the waves coming toward him INCREASES and so he hears the sound at a HIGHER PITCH.

​As the car passes the girl, the frequency of the waves coming toward her is LESS and so she hears the siren at a LOWER PITCH.

Multiple Choice

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

• Amplitude

• Frequency

• Wavelength

• Period

Multiple Choice

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

• It increases

• It decreases

Multiple Choice

You are standing on the side of the road when a police car races past you with its siren on. After the police car passes you, what happens to the pitch of the siren that you hear?

• It increases

• It decreases

• It turns red

Multiple Choice

Look at the picture. Who is experiencing a higher pitched sound?

• Observer A

• Observer B

• There's no difference

Multiple Choice

Long wavelength sound waves are (in the same medium)...

• high pitched

• low pitched
• medium pitched

Multiple Choice

When the car moves AWAY from you, its horn seems...

• Lower pitched

• Higher pitched

• Normal

Multiple Choice

What can you tell about this object's motion?

• Moving to the North (up).
• Moving to the South (down). 
• Moving to the West (left). 
• Moving to the East (right). 

Multiple Choice

What can you tell about the motion of this object?

• Moving left.
• Moving right quickly.
• Standing still. 
• Moving up slowly. 

Multiple Choice

The Doppler effect happens when a wave-making source has motion relative to an observer. 

• True
• False

Multiple Choice

When an ambulance move TOWARD you it sounds ________ pitched. 

• higher

• lower

Multiple Choice

As dad escapes from his kids (the gap between him and the kids is getting bigger), he hears them yelling

• lower pitched than they would normally.

• higher pitched than they would normally.

• the same pitch they would normally.

Multiple Choice

When the apparent frequency of a wave is higher what happens to the wavelength?

• the wavelength gets longer

• The wavelength gets shorter

• the wavelength doesn't change

• I have no idea

Multiple Choice

You stand on the sidewalk next to the street. A fire truck is moving towards 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.

Multiple Choice

What is the Doppler Effect?

• ​The apparent change in frequency of a wavdue to the relative motion of the source (or receiver).

• A change in sound that alters wavelength

• A change in sound that alters frequency

• A change in pitch that causes frequency, sound, light and other waves to disappear