An object at P in water appears to be at P' as seen by an observer in air, as Fig. shows.

Fig.

The paraxial light emitted by P is refracted at the water surface, for which

1.33 sin i 1 = sin i 2

As i 1 , i 2 are very small, we have the approximation 1.33 i 1 = i 2 . Also,

i 2 = α ≈ , i 1 = β ≈ .

Hence, we have

= . = 3 ft.

Let the distance between the apparent location of the fish and the center of the lens be u, then

u = 2 + = 5 ft.

From = + , we have

v = – 6 ft.

Therefore, the image of the fish is still where the fish is, four feet below the water surface.