Title: Doppler Effect
Earth Systems
Standard 1, Objective 1
Title: Doppler Effect
Description: Students will see and hear demonstrations of the Doppler Effect and then make an advertisement for a rock and roll band called “The Doppler Effect”
Materials: coiled phone cord, rope or slinky, computer for each student group or one computer and projector, student page (see below) Construction paper or a printer.
Time needed: 90 minutes if computers are used for the poster, less if students do them by hand.
Background knowledge: This is an introductory activity.
Procedure
1. Review with students what is meant by frequency and how the frequency produces a pitch. This should be review from 8th grade. Use the phone cord or slinky to model a frequency and change it to a longer and shorter wave. Describe how sound changes as the source of the sound is either moving toward them or away from them. Ask them why the pitch of the sound gets higher if the sound source is moving toward them and lower if it is moving away from them. The students moving the slinky or phone cord can model this by moving toward and away from one another (trying to keep the same frequency). Hopefully, through illustrations and examples they will see that the frequency is changing as the source is moving.
2. Play the applets for students or, if they are working independently on computers, they will do this themselves.
3. Have student describe in their own words the reason a police siren sounds different as it approaches you and goes past. Discuss the reading on the student sheet that compares Doppler effect to Red Shift.
4. Describe the poster students will be making for the band “Doppler Effect”. They can use the computers to look for pictures or text or they can draw them.
5. Emphasize that the posters need to have factual information contained in them.
Student SheetName______
Title: Doppler Effect
Introduction: Can you make the sound of a siren or racecar as it goes by you? Even if you can’t, can you think about what happens to the pitch of the sound as it goes by? That change in pitch is the Doppler Effect. It is important to understand because it relates to all moving objects and can help us understand how we know the universe is expanding from the Big Bang. In this activity, you will see and explore several ways we can understand the Doppler effect.
Procedures:
1. Watch as your teacher demonstrates waves with a slinky, phone cord or rope. Draw a wave with a high frequency and a low:
high frequency:
low frequency:
2. What happens to the frequency when the wave makers move toward each other?
How would that sound?
3. What happens to the frequency when the wave makers move away from each other?
How would that sound?
4. Use a computer or watch your teacher use a computer to show the Doppler effect.
These websites show what happens to a moving car:
5. In your own words, why does the pitch of a moving car change as it goes by you?
6. Light travels in waves also. When light is effected by movement, we call it red shift or blue shift because light doesn’t have pitch, it has color. Red has a lower frequency of light and blue is higher. If something is moving away from us, its light spectrum is shifted towards the red end of the spectrum. Fill in the missing labels on this comparison (the waves are not to scale and would be different for sound and light):
Soundpitch
? ?
? ?
color
Light
7. Use the Internet or a textbook to create a poster that advertises a rock and roll group called “The Doppler Effect”. Be creative and make it interesting to look at but also include 5 facts about the Doppler effect. Underline the statements or pictures to show where your facts are.
8. Red Shift refers to how the spectrum of light waves shifts towards the red end when an object is moving away from the observer. Look carefully at the spectra below: