A student find the writing on the blackboard as blurred and unclear when sitting on the last desk in the classroom. He, however, sees it clearly when sitting on the front desk at an approximate distance of 2m from the blackboard. Draw ray diagrams to illustrate the formation of image of the blackboard writing by his eye-lens when he is seated at the (i) last desk (ii) front desk. Name of the kind of lens that would help him to see clearly even when he is seated at the last desk. Draw a ray diagram to illustrate how this lens helps from to see clearly.

Explanation

Defect of vision - myopia (Short-sightedness)
Two causes of this defect: (a) Ciliary muscles get weak, (b) Eye ball gets elongated.
Concave lens is used for the correction of myopic eye (seated at last desk)