Take the 2-minute tour ×
Physics Stack Exchange is a question and answer site for active researchers, academics and students of physics. It's 100% free, no registration required.

Where does the energy go when two photons interfere destructively at a point on a screen in Young's double slit experiment ?

share|improve this question
1  
If energy simply redistributes itself , then what is the explanation of this ? physics.stackexchange.com/questions/23930/… Anna v's answer ? –  user23503 May 3 '13 at 10:55
    
You might as well ask "Where does the energy go at the nodes of a vibrating string?". Answer: to places where the interference is not so destructive. –  dmckee May 3 '13 at 17:42
    
@dmckee What if it is destructive everywhere ? Answer: Energy stays in the very same places , but it changes to other forms . For example suppose I send 2 out of phase waves to a person . The person won't see the waves coming to him but will be getting the energy at the other end of the string. –  user23503 May 4 '13 at 5:22
    
" What if it is destructive everywhere ?" In general that's not how it works. You seem to be assuming that the classical description of E&M and the quantum description will give different results in a realm where they are both valid. They won't. They describe the same physics and where their regions of applicability overlap they give the same predictions. –  dmckee May 4 '13 at 6:07
    
@dmckee When I said destructive everywhere , I was replying in the context of string and not EM waves . Like you said for vibrating string . –  user23503 May 4 '13 at 7:10

1 Answer 1

up vote 1 down vote accepted

Each photon leaves its energy in the molecules of the screen. Destructive interference observed at the line x=1mm for example , means that the probability of finding a photon at x=1 is close to zero. Instead, the photon has very high probabiliy of depositing its energy at the construcive interference fringe.

share|improve this answer
    
Yes , supposedly , the YDSE happens adzactly according to what we predicted using probabilities, then there'll be no heat/energy at the dark fringes ? –  user23503 May 3 '13 at 12:45
    
Also , I'd very grateful if you could once have a look here and tell me if I am correct here or not ? Kindly read the transcript once . Sorry for wasting your time , but kindly read and tell me if there's something that I am understanding .chat.stackexchange.com/transcript/71/2013/5/1 –  user23503 May 3 '13 at 12:49
    
Yes, in a double slit expriment the dark fringe means no energy deposited there. Luboš Motl in his blog has a good formulation of how the individual photon fields build up the classical electromagnetic field motls.blogspot.com/2011/11/… . Sound is different. The energy of sound is propagated on the medium. EM needs no medium. –  anna v May 3 '13 at 13:14
    
But I think you wrote in that post in my question's comment ," when alignment was right , heat was observed at a region of dark fringe ?" –  user23503 May 3 '13 at 13:26
    
That was a possible hypothesis for total destructive interference, no bright fringes. a very special experimental setup, wired.com/wiredscience/2011/02/real-live-antilaser . I was exploring alternatives, and my answer was not popular."Or the truth is in between that the energy propagates and we can only see interference if the beams impinge on a medium, which will take care of energy conservation" –  anna v May 3 '13 at 16:55

Your Answer

 
discard

By posting your answer, you agree to the privacy policy and terms of service.