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Activity 1: Doppler Effect 1. View the applet of the Doppler Effect at

http://www.colorado.edu/physics/2000/applets/doppler.html 2. What happens to the distance between the wave fronts as the police car moves forward or

backward? 3. The speed of sound waves in air is approximately 343 m/s. Why does a person hear a

different frequency if the police car is moving toward or moving away? 4. A French submarine and a U.S. submarine move toward each other during maneuvers in

motionless water in the North Atlantic. The French sub moves at 50.0 km/h, and the U.S. sub at 70 km/h. The French sub sends out a sonar signal (sound wave in water) at 1000 Hz. Sonar waves travel at 5470 km/h.

(a) What is the signals frequency detected by the U.S. sub? (b) What frequency is detected by the French sub in the reflected signal?