What causes shadows to stretch in this way?

Question

With the sun behind me and a pole in front of me I move my hand such that my hand's shadow approaches the pole's shadow. As my shadow draws nearer, the pole's shadow stretches out to meet my hand's shadow (it is always the shadow of the front object that stretches). Why does this occur?

Answer 1

because of diffraction.... and that light is not unidirectional and incoherent.....

when light waves bend around an edge the waves interfere with each other and forms diffraction patterns... but these patterns can not be closely seen... not clear... or not as edgy as the obstacle like your hand or post...

in this case, the edge of your hand and the edge of the post are edges, so when they are close, the 'kissing' of the shadows is the part of the pattern where light waves don't exactly meet the way they should...

Answer 2

Shadows from the sun may appear to be sharp, but they're not. Your eye's instantaneous contrast range is rather limited and cannot resolve the gradations in contrast of the shadow's edge.

However, when two shadows come close together, their combined shadowing creates a sufficiently dark enough region that your eye is able to discern the parts of the individual shadows that your eye's limited contrast couldn't before.

Answer 3

must be a reunion case...