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
