Police radar detects the speed of a car (Fig. P38.15) as fol- lows. Microwaves of a precisely known frequency are broad- cast toward the car. The moving car reflects the microwaves with a Doppler shift. The reflected waves are received and combined with an attenuated version of the transmitted wave. Beats occur between the two microwave signals. The beat frequency is measured. (a) For an electromagnetic wave reflected back to its source from a mirror approaching at speed 2, show that the reflected wave has frequency :+ v where fis the source frequency. (b) Noting that v is much less than c, show that the beat frequency can be written as feat 2v/A. (c) What beat frequency is measured for a car speed of 30.0 m/s if the microwaves have frequency 10.0 GHz? (d) If the beat frequency measurement in part (c) is accurate to +5.0 Hz, how accurate is the speed measurement? %3D SPEED LIMIT 25 YOUR SPEED Figure P38.15 Bbe Bueg o

Police radar detects the speed of a car (Fig. P38.15) as fol- lows. Microwaves of a precisely known frequency are broad- cast toward the car. The moving car reflects the microwaves with a Doppler shift. The reflected waves are received and combined with an attenuated version of the transmitted wave. Beats occur between the two microwave signals. The beat frequency is measured. (a) For an electromagnetic wave reflected back to its source from a mirror approaching at speed 2, show that the reflected wave has frequency :+ v where fis the source frequency. (b) Noting that v is much less than c, show that the beat frequency can be written as feat 2v/A. (c) What beat frequency is measured for a car speed of 30.0 m/s if the microwaves have frequency 10.0 GHz? (d) If the beat frequency measurement in part (c) is accurate to +5.0 Hz, how accurate is the speed measurement? %3D SPEED LIMIT 25 YOUR SPEED Figure P38.15 Bbe Bueg o

Principles of Physics: A Calculus-Based Text

5th Edition

ISBN:9781133104261

Author:Raymond A. Serway, John W. Jewett

Publisher:Raymond A. Serway, John W. Jewett

Chapter24: Electromagnetic Waves

Section: Chapter Questions

Problem 73P: A linearly polarized microwave of wavelength 1.50 cm is directed along the positive x axis. The...

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