Destructive Wave Intference

AugustusMaximus

Small questions. When there is constructive wave interference with light, the light wave that comes out of it increases in size.

What happens when it is destructive. WHere does all the energy go ?

I mean, if this were to happen in a vacuum, it can't come out as heat or sound energy.

Are small amounts of matter such as electrons created when this happens ?

Gurgle

A wave doesn't 'contain' energy, its the propagation (movement) of energy. If 2 waves cancel each other out (destructive interference) then no energy is being moved, its just staying where it is.

AugustusMaximus

What about the case of a two photons of light.

I mean, the two photons are particles with wave like properties.

What happens to both photons in this case considering that both waves are cancelled out ?

JoeB-

He he, it can get confusing when thinking about small quantities...

In the famous slit experiment to show wave interference, the interference effect happens even if you use actual particles.. like electrons... this shows that streams of particles can be considered as waves and will show interference effects. What is most amazing is that the interference effects remain even if the electrons are fired one at a time.. so the individual electrons are interfering with themselves (and passing through both slits at once)!!!!

Disclaimer: I could be wrong.

Michael Collins

JoeBallantine wrote: »

Disclaimer: I could be wrong.

No, you are quite right. The interesting part is the interference dissapears if you try to detect which slit the electron goes through. And Quantum Mechanics is born!

In the original question, you really only think of photons when light interacts with matter. So propagating light in free space should be considered in terms of waves. When waves interfere destructively somewhere, the also interfere constructively somewhere else. So the total energy is always conserved. This is essentially what Gurgle has said.