Suppose there are two cars moving toward each other, the red car honks and the sound wave gets reflected by the white car. Is the frequency of sound wave reflected by the white car the same as the frequency perceived by the driver of the white car?
2007-12-07 11:22:37 · 8 answers · asked by 3.141592653589793238462643383279 3 in Science & Mathematics ➔ Physics
Assume under ideal conditions
2007-12-07 11:28:43 · update #1
If the red car were to honk while stationary it would sound different than if it were moving towards or away from you. While moving closer to you, the sound waves created will be closer together. If the car was moving away, the sound waves would be spaced farther apart, sounding lower. This is why an ambulance sounds different coming towards you than when it is driving away. The frequency percieved by the driver of the white car and the frequency reflected off the white car are the same wave though, so there would be no difference there. Both the car and driver are moving at the same speed and direction relative to the red car so they recieve the same wave.
2007-12-07 11:31:16 · answer #1 · answered by spine1612 2 · 0⤊ 0⤋
No, the frequency perceived by the white car is not the same as the frequency reflected off the white car. The driver of the white car hears the wave Doppler shifted once. When the wave hits the car, it reflects and Doppler shifts another time. So the driver of the red car hears the echo shifted twice.
This is essentially how radar guns work, except electromagnetic waves are used instead of sound waves. The factor of two is very important, or else you'll get half the speed, and then no tickets!
2007-12-07 12:00:01 · answer #2 · answered by z08595 2 · 0⤊ 0⤋
No, assuming you're standing roughly in front of the white car. The original frequency of the horn is shifted up based on the speed the two cars are approaching each other. Whatever this perceived (by the white car driver) shift is, the reflected noise will shift even more since the white car is moving closer still to the listener, so the decrease in distance and consequent compressing of the peaks & valleys of the sound waves is even larger than what the white car driver hears.
Not sure this is a clear explanation, a diagram would make it clearer...
2007-12-07 11:32:23 · answer #3 · answered by VirtualSound 5 · 0⤊ 0⤋
In EM spectrums, the things that affect frequency are material that it is transmitting through and the inclusion of interference. I will assume no interference from the car.
For hearing, the medium is air which is the same as the medium reflected from the car. It will be shifted a little when it goes through the windshield, but I believe it is shifted back when it leaves the glass and into the air again. The only thing that is changed then is the timing (or phase) of the signal so that the driver of the car will hear it a tiny fraction of a second after it actually reflected from the car.
2007-12-07 11:35:59 · answer #4 · answered by Christopher F 4 · 0⤊ 1⤋
The absolute frequency does remain the same.
But since the two cars are in relative motion they hear an apparent change in frequency.
The white car feels the change in frequency and again the red car hears another frequency due to reflection.
2007-12-07 12:35:07 · answer #5 · answered by PlanB 2 · 0⤊ 0⤋
You are the physics person. Tell us the answer. I only have a red car or actually a van so i know the frequency of the sound is greater at my van than the original frequency so I would imagine that the reflected frequency would be hight also but that is not the question. So I guess I don't really know.
2007-12-07 11:29:57 · answer #6 · answered by . 6 · 0⤊ 1⤋
Of course NOT ! include realitivity....wind...thickness of windshield.....hearing capacity....etc... !
2007-12-07 11:27:40 · answer #7 · answered by Anonymous · 0⤊ 1⤋
forget you smart geek!
2007-12-07 11:25:54 · answer #8 · answered by Anonymous · 0⤊ 1⤋