Short-sightedness (myopia) is caused due to the elongation of the eyeball.

$A$ human eye can focus objects at different distances by adjusting the focal length of the eye lens. This is due to

What is the muscular structure located behind the cornea in our eye called?

$A$ $14$ year old student is not able to see clearly the questions written on the blackboard placed at a distance of $5\, m$ from him.
$(a)$ Name the defect of vision he is suffering from.
$(b)$ With the help of labelled ray diagrams show how this defect can be corrected.
$(c)$ Name the type of lens used to correct this defect.

What is near-sightedness?

$A$ man wearing glasses of focal length $+1\, m$ cannot see objects beyond $1\, m$. What is the defect in his eye?