Explain why a stamp placed under a rectangular glass slab appears raised? ?

Question

i need the answer please

Answer 1

The light passing through the glass is 'Refracted' (or Bent) which gives the impression to the viewer that the stamp is above its actual level under the glass.

It's the same effect as when you hold a knife or other utensil in a bowl of water it appears to be bent when viewed from above the water.