Question

What is the observed frequency of a siren with a frequency of

Answer 1

Answer: The observed frequency is 518.6 Hz

Explanation:

By the Doppler Effect, we know that:

f' = ((v + v0)/(v - vs))*f

where f' is the perceived frequency.

v is the velocity of the wave, in this case 330m/s

v0 is the velocity of the receptor, in this case 0m/s

vs is the velocity of the source, in this case -50m/s (the minus sign is because it is coming thowards us)

f is the original frequency, f = 440hz.

then we have:

f' = 440hz*(330m/s)/(330m/s - 50m/s) = 518.6 Hz