Question

20. (a)What is meant by the term ‘power of accommodation’? Name the component of eye that is responsible for the
power of accommodation. 5
(b) A student sitting at the back bench in a class has difficulty in reading. What could be his defect of vision? Draw ray
diagrams to illustrate the image formation of the blackboard when he is seated at the (i) back seat (ii) front seat. State
two possible causes of this defect. Explain the method of correcting this defect with the help of a ray diagram.

Answer 1

Power of accomodation is ability of eve lens to change focal length

Answer 2

The ability the eye lens to adjust the focal length is called accommodation

Ciliary muscle are responsible for power of accommodation

At back seat his defect is myopia it can be corrected by wearing convex lens

At front seat his defect is hypermetropia it can be corrected by wearing concave lens of suitable power