Question

In the evening you go back to the swimming pool with your friends. The object is still lying on the bottom of the pool in the same location as before, but since it's dark now, you use a flashlight to show it to your friends. Remembering the apparent location of the object in daylight, where should you aim to illuminate the object with the flashlight? Assume you hold the flashlight at eye level.
Aim it above point, below point, or same location?

Answer 1

Answer: You should aim at an above point.

Explanation:

The light when it goes from the air to a densier substance as water suffers the effect called refraction in which the relative angle of incidence is different, in general, from the refracted one, as shown in the picture. Since water has greater density than air, then the refracted angle is smaller than the incident angle of the light beam, then to reach the actual location of the object from outside de pool it is necessary to aim a little above the real location, so that the light reaches it.