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Physics Review Question Unit: Waves Year: 1991 Question#: 58 Question: A police officer's stationary radar device indicates that the frequency of the radar wave reflected from an automobile is less than the frequency emmitted by the radar device. This indicates that the automobile is (1 ) moving toward the police officer (2 ) moving away from the officer (3 ) not moving What is this question really asking? Explanation by: Gabriel F [ Return to question menu ] Answer 1 Moving toward the police officer INCORRECT If the car is moving toward the radar gun then the frequency will be higher coming back than the wave emitted by the radar. Consult the Doppler Effect. return to top Answer 2 Moving away from the police officer CORRECT Since the car is moving away from the waves, they are going to strike the car and reflect less rapidly than they were created by the RADAR gun. This is the Doppler effect. return to top Answer 3 Not moving INCORRECT If the car is not moving at all, then the frequency will return to the radar device at the same frequency. Consult the Doppler Effect. return to top What's this question really asking? What is the relationship between the direction of a moving object and an emitted wave from a radar gun? (Can you interpret the Doppler Effect?) return to top |
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