Velocity of source = 36 Kmph
VS = 36 × \(\frac{5}{18}\) = 10 m/s
Velocity of sound v = 340 m/s
Frequency n = 500 Hz
For the sound coming directly from the siren to the listener, source (siren) is moving away from the listener so
VS = -10 m/s V2 = 0
Apparent frequency of the wave
= 485.7 Hz