(a) Find the magnitude of the difference between the frequency of the emitted wa
ID: 2262849 • Letter: #
Question
(a) Find the magnitude of the difference between the frequency of the emitted wave and the wave that returns to the police car after reflecting from the speeder's car.1 Hz
(b) Which wave has the greater frequency? The wave that returns to the police car has the greater frequency. The emitted wave has the greater frequency.
Why?
3 The wave that returns to the police car has the greater frequency. The emitted wave has the greater frequency. Suppose that a police car on the highway is moving to the right at 21 m/s, while a speeder is coming up from almost directly behind at a speed of 32 m/s, both speeds being with respect to the ground. The police officer aims a radar gun at the speeder. Assume that the electromagnetic wave emitted by the radar gun has a frequency of 7.00 times 109 Hz. Find the magnitude of the difference between the frequency of the emitted wave and the wave that returns to the police car after reflecting from the speeder's car. Which wave has the greater frequency? The wave that returns to the police car has the greater frequency. The emitted wave has the greater frequency. why?
Explanation / Answer
a) By doppler effect, new frequency = f*(V+Vreceiver)/(V+Vsource)
As receiver is coming towards wave and source is going away.
New frequency = 7*10^9*(3*10^8+32)/(3*10^8+21)
Again after reflection, source speeder is getting near while receiver cop is getting away
New frequency = 7*10^9*(3*10^8+32)/(3*10^8+21)*(3*10^8-21)/(3*10^8-32)
Therefore change in frequency = 513.33 Hz
b) The reflected wave has greater frequency.
c) Because of the doppler effect. In first case receiver is coming towards wave with greater velocity tha the source which increase frequency and in second case the source is moving towards the receiver with higher speed than the receiver moving away.
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