Why does the bottom of the swimming pool appear shallower than it really is? – Explain in terms of refraction of light.
The correct answer and explanation is:
The bottom of a swimming pool appears shallower than it really is due to the refraction of light as it passes from water to air. Refraction is the bending of light when it moves from one medium to another with a different density. In this case, light travels from water, which is denser than air, to the air above the pool.
When light waves pass from the water to the air, they slow down and bend towards the normal line (the imaginary line perpendicular to the surface at the point of incidence). Since light is traveling from a denser medium (water) to a less dense one (air), the angle at which the light bends causes objects underwater to appear raised or closer to the surface than they truly are. This effect is stronger when the observer is looking from a shallow angle relative to the water surface.
This optical illusion is a result of the difference in the refractive indices of water and air. The refractive index of water is around 1.33, while the refractive index of air is approximately 1.00. The greater the difference between these two indices, the more pronounced the bending of light will be. When looking into the water from above, the light rays coming from the bottom of the pool bend as they exit the water, making the pool floor appear closer to the surface than it is in reality.
This phenomenon is similar to how a straw appears broken or bent when placed in a glass of water. The bending of light causes the straw to look different from what it actually is, and in the case of the swimming pool, it causes the depth to appear less than it really is.