A person suffering from short-sightedness can see clearly up to a distance of $2 \mathrm{m}$. Find the nature and power of the lens required to correct his vision.

What are the causes of the following defects of vision and how can they be corrected?

Cataract      

What are the causes of the following defects of vision and how can they be corrected?

Presbyopia

A person sitting at the back of a class is not able to see what is written on the blackboard. He, however, sees it clearly when sitting on the front seat at an approximate distance of $1.5 \mathrm{m}$ from the blackboard.

(i) Name the defect of the eye he is suffering from. 

(ii) Draw a ray diagram to illustrate the image formation of the blackboard writing by his eye lens when he is seated at the back seat. 

Write the function of the following part of human eye:

Cornea

Write the function of the following part of human eye:

Iris

Write the function of the following part of human eye:

Crystalline lens 

Write the function of the following part of human eye:

Ciliary muscles.

A child is able to read his book comfortably but is unable to read the matter written on the blackboard at a certain distance.

(i) Name the defect of vision he's suffering from.

(ii) With the help of labeled ray diagrams show :

    $\left(a\right)$ the above-mentioned defect of vision.

    $\left(b\right)$ correction of the above-mentioned defect using a suitable lens.