$A$ student finds the writing on the blackboard blurred and unclear while sitting on the last desk in a classroom. He,however,sees it clearly while sitting on the front desk at about $2\, m$ from the blackboard.
$(a)$ 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.
$(b)$ Name the defect of the eye from which the student is suffering.
$(c)$ Name 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 him to see clearly.

(N/A) $(i)$ When the student is seated at the last desk,the image of the distant object forms in front of the retina because the eye lens is unable to focus light rays from distant objects onto the retina.
$(ii)$ When the student is seated at the front desk,the object is closer,and the eye lens can focus the light rays onto the retina,resulting in a clear image.
$(b)$ The student is suffering from myopia (near-sightedness).
$(c)$ The defect can be corrected by using a concave lens of suitable focal length. The concave lens diverges the incoming light rays from the distant object,making them appear to come from the student's far point,thus allowing the eye lens to focus them onto the retina.