Question

A straight stick partly dipped in water obliquely appears to be bent at the surface of the water.

A rod immersed partially and obliquely in water appears to be bent. Explain.

Answer 1

The phenomenon is due to refraction of light.

A ray of light OC coming from O passes from water into air and is refracted away from normal (along CX). Another ray, OD, gets refracted along with DY. The two refracted rays CX and DY, when produced backwards, appear to meet at the point I. Thus, I is the virtual image of the end O of the stick. Therefore, the stick appears to be bent as shown below.

Answer 2

1. Light Refraction: When light passes from one medium (e.g., water) to another (e.g., air), it changes speed and direction. Light rays traveling from the submerged part of the stick (in water) to the observer's eyes (in air) bend away from normal at the water’s surface.
2. Apparent Bending: Due to this bending of light, the part of the stick underwater appears shifted upward. As a result, the stick seems bent at the surface of the water, even though it is straight.