Does Energy Redistribution in Wave Interference Happen Superluminally?


by peter.ell
Tags: energy, happen, interference, redistribution, superluminally, wave
peter.ell
peter.ell is offline
#1
Mar2-12, 04:23 PM
P: 43
Because energy cannot be destroyed, when waves interfere destructively the energy doesn't really disappear, it's simply redistributed to areas of constructive interference, right? But isn't this energy redistribution instantaneous?
Phys.Org News Partner Physics news on Phys.org
Better thermal-imaging lens from waste sulfur
Scientists observe quantum superconductor-metal transition and superconducting glass
New technique detects microscopic diabetes-related eye damage
The_Duck
The_Duck is offline
#2
Mar2-12, 04:29 PM
P: 788
No, the energy flows continuously and always at speeds less than or equal to c.
questionpost
questionpost is offline
#3
Mar2-12, 05:49 PM
P: 198
Quote Quote by The_Duck View Post
No, the energy flows continuously and always at speeds less than or equal to c.
What about when a photon is measured? When you have a radio wave, it expands over many many meters, but then when a device picks it up it becomes measured and the entire photon localizes to that interaction point instantaneously.

eaglelake
eaglelake is offline
#4
Mar2-12, 09:21 PM
P: 128

Does Energy Redistribution in Wave Interference Happen Superluminally?


Quote Quote by peter.ell View Post
Because energy cannot be destroyed, when waves interfere destructively the energy doesn't really disappear, it's simply redistributed to areas of constructive interference, right? But isn't this energy redistribution instantaneous?
There is no redistribution of energy going on here!

Here, we are discussing classical waves that carry energy and momentum as they propagate through a vibrating medium. The wavefunction [tex]\psi (\vec r,t)[/tex] represents the displacement of the vibrating medium from its equilibrium position. In an interference experiment, some parts of the vibrating medium have a greater displacement than normal (constructive interference) and other regions have no displacement at all (destructive interference).

Where destructive interference occurs, the medium is not vibrating. That region never was vibrating. There is no such thing as “interference of displacements”. The medium can only vibrate in one direction at a time. It is impossible to get a medium to vibrate in opposite directions at the same time so that the total displacement “cancels out”. We need not worry about energy not being conserved.

If we set up the experiment so that interference occurs, then there are regions in the medium of enhanced displacement and regions of no displacement. Those regions are always there. There is no sudden destruction of the displacement going on and, likewise, there is no sudden transfer of energy from the “destructive” region to the “constructive” region in order to save conservation of energy.

Best wishes


Register to reply

Related Discussions
Would constructive interference still happen if no mirror at confluence point Quantum Physics 0
Where does photon interference happen Quantum Physics 0
Energy conservation in wave interference.... General Physics 7
Interference does not happen General Physics 9
Wave interference and energy conservation Classical Physics 1