A coin is dropped in a swimming pool filled up with water. A man approaching the pool is just able to see the coin when he is at a distance of 1 metre from the edge of the pool. Next day the water of the pool was drained out. Now, at what distance from the edge, the coin will be just visible?
Less than 1 metre
In the experiment 'The reappearing coin', we had seen that pouring water into a bowl makes its bottom visible to even more distant person due to deviation of light coming from water to air. That deviation we call refraction.
Applying same concept we can say, when the water is there in the pool, the coin is visible from even farther distance. So, when the water is removed, the person will have to approach the pool a little more to see the coin.