A student sitting at the back of the classroom cannot read clearly the letters written on the blackboard. What advice will a doctor give to her? Draw ray diagram for the correction of this defect.

AcademicPhysicsNCERTClass 10

She is suffering from a defect called myopia $(short-sightedness)$.  This defect can be corrected by using concave lenses in her spectacles.


Myopia, also known as near-sightedness or short-sightedness, is a defect of vision in which a person can\'t see the distant object clearly (appears blurred), though can see the nearby objects clearly. The far point of a myopic eye is less than infinity.

This defect occurs either due to the high converging power of the eye lens, (because of its short focal length). Or, due to the eye-ball being too long, which causes light to focus in front of the retina, instead of directly on the retina. 

It is corrected by using spectacles containing concave lenses, which should be of such a focal length (or power) that it produces a virtual image of the distant object (lying at infinity) at the far point of the myopic eye.

Updated on 10-Oct-2022 13:27:45