in autumn when trees have shed all their leaves,one can frequently see shadows from two parallel branches.the lower branch produces a sharp dark shadow and the upper brancha broder and lighter one.if two such shadows are accidentally superimposed,one can see abright light stipein the middle of the darker shadow,so that the shadow seems to be a double one.how do u explain this phenomenon?
1The branches act like a opening and the two light rays are in same phase difference so they form an interference pattern.
And the broader and lighter shadow from upper branch because it is more far from the screen ( i.e. the ground ).
P.S. It is just a guess :P
