Keshav enters a dark room from a brightly lit area. He experiences difficulty in viewing objects, but gradually his vision improves.

Explain the role of the photoreceptors in this case.

During light adaptation:

1. Rods and cones become active.
2. Rods and cones become inactive.
3. Rods become active and cones inactive.
4. Cones become active and rods inactive.

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.

(a) Name the defect of the eye Mahesh is suffering from.

(b) Where is the image formed in this defect?

(c) Mahesh consults an eye doctor and is prescribed suitable lenses to correct the defect. Which type of lens do his spectacles have?