The Doppler Effect J Gabrielse Reading Quiz 1

The Doppler Effect J. Gabrielse

Reading Quiz 1. Give an example of resonance in a closed pipe. 2. What is the difference between a node and an anti-node? 3. Would a tuning fork or a clarinet produce a more complex waveform? 4. What is the term used to describe an oscillation of wave amplitude? 5. What does the human ear convert sound waves into? J. Gabrielse

Listen (QUIETLY!) • On a half sheet of paper write: – What do you think happened? – How did you know? J. Gabrielse

How to See the Doppler Effect • The Doppler Effect has to do with waves. • First, we are going to look at water waves since they are easier to see than sound waves. J. Gabrielse

Imagine Dropping Rocks in a Bathtub One After the Other What would the surface of the water look like? J. Gabrielse

Stationary Wave Source J. Gabrielse

Imagine Moving As You Drop Rocks What would the surface of the water look like? in a Bathtub One After the Other J. Gabrielse

Moving Wave Source J. Gabrielse

Sound Waves Act the Same Way • Let’s listen again J. Gabrielse

You hear the frequency of sound waves as pitch. High frequency/pitch. Low frequency/pitch. • High pitch sound waves come closer together. • Low pitch sound waves come further apart. J. Gabrielse

Stationary Wave Source Wherever you listen, you hear the same pitch. The waves come to each ear at the same frequency. J. Gabrielse

Why is the pitch the same everywhere? Frequency is the same everywhere. λ λ f f L R Stationary Wave Source J. Gabrielse

Moving Wave Source Pitch is not the same everywhere. J. Gabrielse

Pitch depends on how the wave source is moving relative to the listener. Why isn’t pitch the same everywhere? J. Gabrielse

Answer: The Doppler Effect Frequency is higher when the wave source is coming closer. λ f Frequency is lower when the wave source is going away. L λ f R Moving Wave Source J. Gabrielse

Summary: The Doppler Effect What you hear is pitch. Pitch depends on frequency. Frequency is inversely proportional to wavelength. λ The wavelength depends on relative speed. So the frequency depends on relative speed. f L λ f R What pitch you hear depends on relative speed. J. Gabrielse

Question 1: Vote with Your Fingers What will you hear if a car is coming towards you? A lower pitched sound than the driver. The same pitched sound as the driver. A higher pitched sound than the driver. J. Gabrielse

Question 2: Vote with Your Fingers What will you hear if a car is driving away from you? A lower pitched sound than the driver. The same pitched sound as the driver. A higher pitched sound than the driver. J. Gabrielse

Listen: One Last Time L R • What’s happening? • How do you know? This will be on the test. J. Gabrielse

J. Gabrielse