Destructive Interference

[G1SG2]

Two waves need to be 180 degrees out of phase in order to interfere destructively, right? If it were 90 degrees, then one wave would be at maximum/minimum amplitude when the other wave was at equilibrium/at the 0 position, and this would not affect either wave and not qualify as destructive interference, right? Thanks.

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[sv3]

Two waves need to be 180 degrees out of phase in order to interfere destructively, right? If it were 90 degrees, then one wave would be at maximum/minimum amplitude when the other wave was at equilibrium/at the 0 position, and this would not affect either wave and not qualify as destructive interference, right? Thanks.

I can only answer that 180 out of phase would be destructive, yes.
The other parts i dont know. I didnt cover this but it popped up in one question and i just memorized. One of those things i unfortunately don't understand.

 

[Tokspor]

Two waves need to be 180 degrees out of phase in order to interfere destructively, right? If it were 90 degrees, then one wave would be at maximum/minimum amplitude when the other wave was at equilibrium/at the 0 position, and this would not affect either wave and not qualify as destructive interference, right? Thanks.

Since the wave at equilibrium has an amplitude of 0, it has no value, negative or positive, to add (superimpose) to the first wave. The total amplitude would just be that of the first wave.

 

[wanderer]

Two waves need to be 180 degrees out of phase in order to interfere destructively, right? If it were 90 degrees, then one wave would be at maximum/minimum amplitude when the other wave was at equilibrium/at the 0 position, and this would not affect either wave and not qualify as destructive interference, right? Thanks.

0 or 360 degrees is constructive interference
180 is destructive interference
Anything else is just interference.


Not really sure what something like 179 or 1 degree would qualify as but I wouldn't worry about it.

 

[sv3]

0 or 360 degrees is constructive interference
180 is destructive interference
Anything else is just interference.[/QUOTE]

but at 90 its not right?

 

[wanderer]

0 or 360 degrees is constructive interference
180 is destructive interference
Anything else is just interference.[/QUOTE]

but at 90 its not right?

Just plain old interference. In destructive interference the "net wave" has an amplitude that is less than or equal to the contributing waves at all points, or if the two waves are identical in amplitude then it is zero at all points. If it's at 90 there will still be a non zero wave as a result of the supposition.

 

[sv3]

Just plain old interference. In destructive interference the "net wave" has an amplitude that is less than or equal to the contributing waves at all points, or if the two waves are identical in amplitude then it is zero at all points. If it's at 90 there will still be a non zero wave as a result of the supposition.

I'm just trying to confirm what an above poster said about at 90 degrees since the amp is 0, it has no effect?

just piecing together what your both saying to create the pic in my head

thanks again

 

[wanderer]

I'm just trying to confirm what an above poster said about at 90 degrees since the amp is 0, it has no effect?

just piecing together what your both saying to create the pic in my head

thanks again

I wouldn't say that it has no effect. Yes when one wave is exactly 90 and one is 0 (or 180) then one will have an amp of 0. But if one wave is at 45 and the other is at 135 (or any set that doesn't include 0,90,180 or 270) they will both have non-zero amplitudes.