
Interference
Constructive and Destructive Interference
In this animation, the north magnetic fields are shown in red and the south magnetic fields are shown in blue. The upper row of photon fields is provided for reference. The lower row is two separate groups of photon fields as they move. This illustrates the destructive interference when the red fields overlap the blue fields. At the top are the waveforms of the two rows of photons fields. When the waveforms are in phase we see constructive interference and the light level increases. When the waveforms are 180 degrees out of phase we have destructive interference and the light goes dark. Light plus light equals dark in that situation. This darkening is due to the energy flows in the north magnetic field and the south magnetic fields canceling each other so that the energy supplied to the photon itself ceases.
Now you know why there are dark areas and bright areas in the interference patterns above. It is all about the energy flows within the fields around each photon.