Explain why a pencil appears bent when it is partially subme…

When light travels from water (denser) to air (rarer), it speeds up and bends away from the normal (an imaginary vertical line). Since our brains assume light travels in a straight line, we trace these bent rays back to a higher position. This creates an apparent depth that is shallower than the actual depth, making the submerged part look shifted or “bent” at the surface.