A car moving with a velocity of 36 km/hr crosses a siren of frequency 500 Hz. The apparent frequency of siren after passing it will be
Options
(a) 520 Hz
(b) 485 Hz
(c) 540 Hz
(d) 460 Hz
Correct Answer:
485 Hz
Explanation:
Velocity of the car = 36000 m / 3600 s = 10 m/s
ʋemitted = 500 Hz, ʋsound = 330 m/s
ʋobs = ʋemitted [(ʋsound – ʋobs) / ʋsound]
Observed frequency ʋobs = 500 [(300 – 10) / 300]
⇒ ʋobs = 485 Hz