Refraction of Light

Recently, in the Term 3 Science topic Physics, I have learned about an interesting topic of Science, which is refraction of light. Basically, this is a change of the direction of light due to an increase or decrease in its speed. This can be observed when light changes medium at any other degree other than 90°. As we all know, the angle of incidence is between the incident ray and the normal. As for the angle of refraction, it it just the angle between the refracted ray and the normal.

But why does the light ray bend closer towards the normal when it enters from air to another medium, for example water, or glass? This is because water and glass are optically denser than air, in which glass is the most dense, therefore the velocity of light decreases while passing through these medium, and therefore it travels closer towards the normal. However, this cannot be observed when light travels through another medium at a right angle. This is because it travels through the medium in a straight line and is not refracted. This is why when hunting for fish, birds have to overcome the problem of refraction, as the fish seem to be closer to the surface of the water, however, they would not have this problem if they were to hunt the fish from directly above, when refraction is minimized.