Concepts of Physics

IIT JEE Physics (1978-2018: 41 Years) Topic-wise Complete Solutions

Advantage of having Two Eyes


To know the advantage of having two eyes.


glass, coin



Keep a glass of water on a table. Ask your friends to sit about 5 metre from the table. Hold a coin in your hand and move it slowly near the glass. One by one your friends should cover one eye and say when the coin is just above the glass. When they say so, drop the coin. You will find that in most cases your friends judge the position of the coin wrongly, and the coin falls outside the glass. But if they look through both the eyes, they will be able to judge the position of the coin correctly most of the time, and the coin will drop into the glass. This happens because we are unable to judge depth, or the relative distance between objects, with one eye, especially when the objects are at some distance from the eye. Two eyes are required to perceive depth. Also, we can see a wider area with two eyes than with one eye.