The human eye forms the image of an object at its

$(i)$ What is the least distance of distinct vision for a normal eye?
$(ii)$ Does the above distance increase or decrease for a long-sighted eye (hypermetropia)? Give a reason for your answer with a diagram.

$A$ person cannot see objects farther than $12\, m$ from the eye clearly. Name the defect of vision he is suffering from and the lens that should be used for correction of this defect. Illustrate with the help of a diagram,how this lens will correct the defective vision?

Presbyopia is a type of far-sightedness.

$A$ $14$ 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.

How can a change in the size of the eyeball be a reason for $(a)$ Myopia and $(b)$ Hypermetropia? Compare the size of the eyeball with that of a normal eye in each case. How does this change in size affect the position of the image in each case?