A stationary surface emits sound of frequency $$f0=492$$ Hz. The sound is reflected by a large car approaching the source with a speed of $$2$$ ms−$$1$$ . The reflected signal is received by the source and superposed with the original. What will be the beat frequency of the resulting signal in Hz? (Given$$ that the speed of sound in air is $$330$$ ms−$$1$$ and the car reflects the sound at the frequency it has $$received).

Question

A stationary surface emits sound of frequency $$f0=492$$ Hz. The sound is reflected by a large car approaching the source with a speed of $$2$$ ms−$$1$$ . The reflected signal is received by the source and superposed with the original. What will be the beat frequency of the resulting signal in Hz? (Given$$ that the speed of sound in air is $$330$$ ms−$$1$$ and the car reflects the sound at the frequency it has $$received).

Infinity Learn · Accepted Answer

frequency of  sound received by car is $$f1=V+2V492$$      here $$V=330ms$$−$$1$$ Reflected sound from the car will have a frequency $$f2=VV$$−$$2f1$$ $$=VV$$−$$2V+2V492$$ $$=V+2V$$−$$2492$$ Beat frequency $$=f1$$−f        here $$f=492Hz=V+2V$$−$$2492$$−$$492=V+2$$−V−$$2492V$$−$$2=4$$×$$492328=6$$

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