Boojho while waving his hand very fast in front of his eyes, observes that his fingers appear blurred. What could be the reason for it?

The impression of an image does not vanish immediately from our retina but persists there for 1/16 th of a second. So, if we move or hands at a rate faster than this then it will appear as moving in a blurred manner. This is what happening with Boojho as his fingers are appearing blurred due to the fast movement of his hand.