Understanding Why a Fish Appears Higher in Water

When a person stands on the bank of a river and looks at a fish inside the water, they are observing the fish through two different media: water and air. Light rays originating from the fish travel through water and then enter the air before reaching the observer's eyes.

Water is optically denser than air. When light travels from a denser medium (water) to a rarer medium (air), it bends away from the normal at the interface between the two media (the surface of the water).

Let's visualize this:

• Imagine light rays coming from the actual position of the fish.
• As these rays cross the water surface and enter the air, they bend away from the perpendicular line (normal) drawn at the point of entry.
• The observer's brain perceives the object (the fish) as being located along the straight lines formed by these bent rays entering their eyes.
• Because the light rays bend away from the normal, these apparent straight lines appear to originate from a point that is higher than the actual position of the fish.

This phenomenon is known as refraction of light, and it causes objects in a denser medium, when viewed from a rarer medium, to appear shallower than their actual depth. The depth at which the fish appears to be is called the 'apparent depth', and it is less than the 'real depth'.

Therefore, the fish appears to be raised from its original position. It is seen 'just above' its actual location.

Based on this principle of refraction and apparent depth, let's evaluate the options:

• At the same depth but on the right hand side of the original position: Incorrect. The apparent depth is different from the real depth.
• At its original position: Incorrect. Refraction causes a shift in the apparent position.
• Just above the original position: Correct. The apparent depth is less than the real depth, making the fish appear raised.
• Just below the original position: Incorrect. The apparent depth is less than the real depth, not more.

Thus, a person standing on the bank of a river observes a fish inside the water appearing just above its original position due to the refraction of light.