More Applications

Before a photons takes a particular paths it considers all possible paths. The probability of it taking a particular path or ending up in a certain place is calculated by adding up the phasor arrows for all the alternatives and squaring the resultant.

In General

Photons will most probably take the shortest, quickest path. (But, when lots of photons are involved many don't.)

When calculating the probability of a photon arriving at a particular place we need only consider the most obvious paths.

Here are a few more situations which can be explained with this many paths model.