The Doppler Effect

May 20, 2013

Objectives

1. Identify the Doppler effect

2. Explain its cause and uses

3. Understand the terms and cause of Sonic Boom

Doppler Effect

Fire Engine Car Horn

Change in frequency due to the motion of the vibrating object

The Doppler Effect

Sound Waves

1. As an object moves toward you, frequency seems shorter – higher pitch

2. As an object moves away, frequency seems longer – lower pitch

3. Never the speed that changes, just the frequency

The Doppler Effect

Uses of the Doppler Effect

Doppler Radar Police Radar

Wave Barrier and Bow Waves When the source is moving as fast as

the waves it produces it reaches a wave barrier

Once it passes its wave speed is creates a V shaped pattern – Bow Wave

Shock Waves and Sonic Booms

Shock Waves – Form overlapping cones that Form a V

Sonic Boom – sharp crack heard when supersonic aircraft’s shock waves pass

The Sonic Boom

Doppler Demo's

Light Waves

1. Red shift – frequency is lower therefore red light is seen

2. Blue shift – frequency is higher therefore blue light is seen

The Stars

Scientists use this knowledge to measure the speed of rotation of the stars

And the distance of galaxies