The siren of a police car produces a sound of frequency 420Hz.A man sitting next to the road notices that the pitch of the sound changes as the car moves towards and then away from him.1- WRITE DOWN THE NAME OF THE PHENOMENON. 2-ASSUME THAT THE SPEED OF THE SOUND IN AIR IS 340m.s^-1. CALCULATE THE FREQUENCY OF THE SOUND OF THE SIREN OBSERVED BY THE MAN,WHEN THE CAR IS MOVING TOWARDS HIM AT A SPEED OF 16m.s^-1.
In the general doppler equation here, Vr will be zero, the man is still.
http://en.wikipedia.org/wiki/Doppler_effect
1- The phenomenon that causes the pitch of sound to change as the car moves towards and away from the man is called the Doppler effect.
2- To calculate the frequency of the sound observed by the man when the car is moving towards him, we need to consider the Doppler formula.
The formula for the observed frequency (f') due to the Doppler effect when the source is moving toward an observer is:
f' = (v + vo) / (v + vs) * f
Where:
- f' is the observed frequency
- f is the actual frequency of the source
- v is the speed of sound in air (given as 340 m/s)
- vo is the speed of the observer relative to the medium (which is the man's speed, given as 0 m/s)
- vs is the speed of the source relative to the medium (which is the car's speed towards the man, given as -16 m/s since the car is moving towards the man)
Plugging the values into the formula:
f' = (340 + 0) / (340 - 16) * 420 Hz
Simplifying the calculation:
f' = 340 / 324 * 420 Hz
f' ≈ 439 Hz
Therefore, the frequency of the sound observed by the man when the car is moving towards him at a speed of 16 m/s is approximately 439 Hz.