Question

Give scientific resons:
a. Simple microscope is used for watch repairs.
b. One can sense colours only in bright light.
c. We cannot clearly see an object kept at a distance less than 25 cm from the eye.

Answer 1

a. Simple microscope has convex lens which has the ability to produce 20 times larger as well as erect image of an object. This means the magnifying power of the microscope is very high. Thus, simple microscopes are used by watch makers to see the small parts and screws of the watch while repairing it.

b. The cells present on the retina and responsible for colour vision are known as cone cells. These cells become active only under bright light and remain inactive under dark. Thus, we are able sense only in bright light.

c. We cannot clearly see an object kept at a distance less than 25 cm from the eye. This is because ciliary muscles of our eyes are unable to contract beyond certain limit. If the object is placed at a distance less than 25 cm from the eye, then the object appears blurred because light rays coming from the object meet behind the retina.