Does this engaa waves question even make sense??
https://postimg.cc/vcp0V9S4
after equating 180 out of phase to pi,
solving pi = (2pix6)/lambda
gives lambda = 12 for wavelength, so freq = 336/12 = 28.
but I dont get why the answer is instead D) = 56, one solution online says to ignore 180 phase diff and to pretend they are in phase as its equivalent, but it gives a different answer??...
and that the path difference = 6 = 1 wavelength, pi phase difference is normally associated with 1/2 a wavelength???
quite confused.
after equating 180 out of phase to pi,
solving pi = (2pix6)/lambda
gives lambda = 12 for wavelength, so freq = 336/12 = 28.
but I dont get why the answer is instead D) = 56, one solution online says to ignore 180 phase diff and to pretend they are in phase as its equivalent, but it gives a different answer??...
and that the path difference = 6 = 1 wavelength, pi phase difference is normally associated with 1/2 a wavelength???
quite confused.
Original post by MonoAno555
https://postimg.cc/vcp0V9S4
after equating 180 out of phase to pi,
solving pi = (2pix6)/lambda
gives lambda = 12 for wavelength, so freq = 336/12 = 28.
but I dont get why the answer is instead D) = 56, one solution online says to ignore 180 phase diff and to pretend they are in phase as its equivalent, but it gives a different answer??...
and that the path difference = 6 = 1 wavelength, pi phase difference is normally associated with 1/2 a wavelength???
quite confused.
after equating 180 out of phase to pi,
solving pi = (2pix6)/lambda
gives lambda = 12 for wavelength, so freq = 336/12 = 28.
but I dont get why the answer is instead D) = 56, one solution online says to ignore 180 phase diff and to pretend they are in phase as its equivalent, but it gives a different answer??...
and that the path difference = 6 = 1 wavelength, pi phase difference is normally associated with 1/2 a wavelength???
quite confused.
If the sound is a minimum, they arrive out of phase. So wavelength is 6 (one wavelength apart of 18 and 24) and frequency 336/6 = 56.
(edited 6 months ago)
one of the speakers being 180 degrees out of phase flips the positions of maxima and minima compared to what you'd get if they were in phase.
so I guess the 'helpful' answer is telling you to pretend the sources are in phase and then find the lowest frequency that'd give you a maxima at the given position...
or another way of looking at it is the microphone is a whole number of wavelengths distant from each speaker and the 180 degree phase shift of the sources is causing the destructive interference that gives the minima.
gcd (18, 24) = 6 so lambda is 6m
336/6= 56Hz
so I guess the 'helpful' answer is telling you to pretend the sources are in phase and then find the lowest frequency that'd give you a maxima at the given position...
or another way of looking at it is the microphone is a whole number of wavelengths distant from each speaker and the 180 degree phase shift of the sources is causing the destructive interference that gives the minima.
gcd (18, 24) = 6 so lambda is 6m
336/6= 56Hz
Original post by mqb2766
If the sound is a minimum, they arrive out of phase. So wavelength is 6 (one wavelength apart of 18 and 24) and frequency 336/6 = 56.
I see, but I am confused on when path difference is/isnt equal to 1 wavelength in general and does this only apply to waves that are out of phase?
Original post by MonoAno555
I see, but I am confused on when path difference is/isnt equal to 1 wavelength in general and does this only apply to waves that are out of phase?
Just take a simple example (sketch the waves). If one arrived 1/2 wave length different (so 3m difference with 6m wave length), theyd be in phase so a maximum. The distances need to a wavelength or 2 wavelengths or 3 ...) apart to preserve the out of phase property they have at the start.
(edited 6 months ago)
Original post by mqb2766
Just take a simple example (sketch the waves). If one arrived 1/2 wave length different (so 3m difference with 6m wave length), theyd be in phase so a maximum. The distances need to a wavelength or 2 wavelengths or 3 ...) apart to preserve the out of phase property they have at the start.
https://postimg.cc/069TwH8N
Is this correct?
Original post by MonoAno555
Sort of, but Id have sketched the 24 and 18 distances so what would happen if the second distance was 21 with lambda = 6 ... Obviously if the numbers were very large you could simplify them down as appropriate but 3 or 4 wavelengths here is fairly manageable.
Remenber the equation:
delt X=n(delt fi)/(2pi)*lambda
And you can solve nearly 90% of questions about wave in the ENGAA
delt X=n(delt fi)/(2pi)*lambda
And you can solve nearly 90% of questions about wave in the ENGAA
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