A teacher drew the diagram of heart on the blackboard and told the students to copy it in their notebooks. Mahesh couldn’t see the diagram clearly as it appeared blurred to him.
Mahesh consults an eye doctor and is prescribed suitable lenses to correct the defect. Which type of lens do his spectacles have?
Topic: Correction of myopia
Answer
A CONCAVE (diverging) LENS.
A concave lens DIVERGES the light rays slightly before they enter the eye. The over-converging eye then has less bending left to do, and the focus is pushed BACK onto the retina.
THE PAIR to learn together: MYOPIA — image IN FRONT of the retina — CONCAVE lens HYPERMETROPIA and PRESBYOPIA — image BEHIND the retina — CONVEX lens
A way to keep them straight by shape: a CONCAVE lens is thin in the middle and spreads rays apart; a CONVEX lens is thick in the middle and brings them together. If the image is forming too early, you need to spread the rays — concave.
Parts (a), (b) and (c) of this question form one chain — defect, image position, lens — and getting the first right makes the other two follow.