Fish Apparent Position Using Refraction in Water

[physicsmaths1613]

Homework Statement

A fish is 60 cm under water. A bird directly overhead looks at the fish. If the bird is 120 cm above the water level, find the apparent position of the fish as seen by the bird.

The question is solved by using the principles of refraction. But, if the bird is directly overhead, there should be no bending of the light rays. Then why do we use refraction here?

 

[Buzz Bloom]

Hi pm1613:

I suggest that you consider how far underwater the fish appears to be from the perspective of the bird.

Regards,
Buzz

 

[haruspex]

Homework Statement

A fish is 60 cm under water. A bird directly overhead looks at the fish. If the bird is 120 cm above the water level, find the apparent position of the fish as seen by the bird.

The question is solved by using the principles of refraction. But, if the bird is directly overhead, there should be no bending of the light rays. Then why do we use refraction here?

From a given point on an object being viewed, light rays go out in all directions. Some of these fall on the lens of your eye, and are brought back together by the lens to focus on your retina. If, along the way, they pass from water into air, they will diverge a little at that boundary. If you project the diverged lines back under water, they will meet at a point closer to the surface than the actual object. That is where you will perceive the object to be.