A swimming pool appears deeper than its actual depth. Its reason is

A swimming pool appears deeper than its actual depth due to refraction (option A). Refraction occurs because light changes speed and direction as it passes from water (which has a higher refractive index) to air (which has a lower refractive index). When viewing the pool from above the water’s surface, light rays from the bottom of the pool are refracted as they exit the water, bending away from the normal. This bending causes the rays to reach the observer’s eye at a shallower angle than if there were no refraction, making the pool’s depth appear greater than it actually is. This optical illusion is why objects underwater, such as the bottom of a swimming pool, seem displaced from their true positions when viewed from above the water’s surface. Therefore, refraction is responsible for the visual effect that makes a swimming pool appear deeper than its physical depth when observed from outside the water.