Explain how, a hair dresser makes you see hair at the back of your head after the hair cut is complete.

The phenomenon that applies here is multiple reflection that provides the image of back of the head to be viewed. A person is made to stand in front of a mirror and another mirror is held at the back of the head. The reflection from the mirror at the back is visible in the mirror in front of the person and hence the hair at the back of the head is visible to the person in the front mirror.