As you stand near a railroad track, a train passes by at a speed of 31.7 m/s while sounding its horn at a frequency of 218 Hz. What frequency do you hear as the train approaches you and what frequency while it recedes?

Explanation:

Given that,

Frequency of train horn, f = 218 Hz

Speed of train,

The speed of sound, V = 344 m/s (say)

The speed of the observed person,

(a) When the train approaches you, the Doppler's effect gives the frequency as follows :

(b) When the train moves away from you, the Doppler's effect gives the frequency as follows :

Hence, this is the required solution.

causes

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cities become more industrialized

human population grows worldwide