# Interference and photons

1. Sep 22, 2007

### free_electron

What is the current interpretation of the interference of two plane waves in the photon picture?

Does a photon still possess the properties of its plane wave form? What is the meaning of the intensity maxima and minima?

2. Sep 23, 2007

### meopemuk

Photon is a quantum particle. So, the propagation of its wave function is described by the Schroedinger equation. If you solve this equation for the double-slit configuration, and if you take the square of the photon's wavefunction in the vicinity of the photographic plate, you'll obtain the same sequence of maxima and minima which is measured in experiment and which is called the interference picture.

The (quantum) mechanism of formation of the interference picture is the same for one photon and for the flux of billions of photons that we normally call the light wave.

Eugene.

3. Sep 23, 2007

### free_electron

Okay, so a single photon exhibits all the maxima and minima simultaneously? What about the photon wavefunction just before and just after the two slits?

4. Sep 23, 2007

### fleem

There is no consensus for the interpretation. We have phrases like superposition, decoherence, multiple universes, Copenhagen interpretation, hidden variables. These are all interpretations (or refusals to interpret), and arguments on which is best still rage.

5. Sep 23, 2007

### ZapperZ

Staff Emeritus
If you have access, this is a good paper to read:

T. Marcella, Eur. J. Phys. v.23, p.615 (2002).

Zz.

6. Sep 23, 2007

### meopemuk

Of course, just shooting one photon through the slits once you'll not get the interference picture. To get maxima an minima you'll need to repeat this experiment many times. But it seems that each photon "knows" about interference and it has a higher chance to fall into the "maximum" area than into the "minimum" area.

In most optics textbooks you can find a picture of EM wave passing through two slits. The (real part of) wavefunction looks exactly the same. You can also use the Huygens principle to find it qualitatively.

Eugene.

7. Sep 26, 2007

### free_electron

Thanks, all. I would be interested in any reference which solves Schrodinger's equation for a photon going through 2 or more slits. TIA.

8. Sep 26, 2007

### meopemuk

You can find discussions of the double-slit interference based on the Huygens principle in any optics textbook. The same arguments are qualitatively valid for photon's wave function satisfying the Schroedinger equation. Also you can take a look at Feynman's books and lectures. It was his favorite topic.

Eugene.