The frequency of a train horn is 500 Hz. Assume the speed of sound in air is 340 m/s. What is the frequency heard by an observer if the observer is moving toward the train with a speed of 30.0 m/s and the train is moving toward the observer at 30 m/s?

Question

anonymous · Answer

500 hz = 500 oscillations per second therefore the wavelength of 500 hz at 340m/s is 1.470 meters. When the train is heading towards an observer, at 30m/s and same with the observer it will be 60m/s total. The difference is now 400 m/s therefore we can assume that the frequency is now 588 Hz (1.470*400).

anonymous · Answer

Thank-you very much!

anonymous · Answer

you need to recheck...
$$f _{observer}=f _{source}(v _{sound} + v _{observer})/(v _{sound} - v _{source})$$$$f _{observer}=500Hz(370/310)=596.8Hz$$