Explain why a tank filled with water or swimming pool looks shallower. Explain with the help of a ray diagram.

Explanation

To an observer, a swimming pool or a tank filled with water appears shallower due to the phenomenon of refraction of light. The bottom of the pool or the tank appears to be raised. Two light rays starting from the edge of the object (O) kept at the bottom of the pool gets refracted at the water - air interface. The light rays move from a denser (water) to a rarer medium (air), hence they bend away from the normal. On externding the diverging rays, they appear to meet at point 1 to form the image which is virtual and appear to be raised. The distance of the object from the surface of water is called the Real depth and the distance of the image from the water surface is called Apparent depth. Apparent depth is less than the real depth. Therefore the bottom floor of the pool or an object at the floor of the pool appears to be raised.