Doppler - Basics

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

• Low pitched
• High pitched
• Normal

When an ambulance move TOWARD you it sounds ________ pitched. 

• high
• low
• medium

The Doppler effect is seen when a wave-making source moves at a velocity that is constantly perpendicular to an observer.

• True

• False

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). 

What can you tell about the motion of this object?

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

An observer passes a 500 Hz sound source and moves away with a speed of 30 ms^-1. The speed of sound is 330 ms^-1.

The frequency heard by the moving observer is

• 458.3 Hz

• 544 Hz

• 460 Hz

• 548 Hz

A siren is generating a wave with a frequency of 10Hz while moving. An observer uses a wave detector and measures the frequency as 5Hz. What can you conclude about the motion of the siren?

• The siren is moving towards the observer because the wavelength is shorter

• The siren is moving away from the observer because the amplitude is lower

• The siren is moving towards the observer because the frequency is lower

• The siren is moving away from the observer because the frequency is lower

Sonic boom is when . .

• An object travels fractionally slower than the speed of sound. The energy of the sound waves pile up to form a shock wave.

• An object travels as fast as the speed of sound. The energy of the sound waves pile up to form a shock wave.

• An object travels faster than the speed of sound. The energy of the sound waves pile up to form a shock wave.

• An object travels faster than the speed of sound. The energy of the sound waves spread out to form a shock wave.

The speed of sound is 330 ms^-1. A motorcycle moving at 45 m/s sounds its horn (250 Hz) passing by a pedestrian. What sound does the pedestrian hear when the motorcycle approaches?

• 203.65 Hz

• 456Hz

• 786 Hz

• 289.47 Hz

The speed of sound is 330 ms^-1. A motorcycle moving at 45 m/s sounds its horn (250 Hz) passing by a pedestrian. What sound does the pedestrian hear when the motorcycle moves away?

• 220 Hz

• 210 Hz

• 156.65 Hz

• 289.47 Hz