The circular part in the centre of the retina is called:

$A$ person cannot see an object clearly if it is placed beyond $100 \, cm$. Find the power of the lens required to see an object clearly at infinity.

$A$ person cannot see objects clearly placed at a distance of more than $40 \, cm$. He is advised to use a lens of power:

$A$ person can see objects clearly only when they lie between $50\, cm$ and $400\, cm$ from his eyes. In order to increase the maximum distance of distinct vision to infinity, the type and power of the correcting lens the person has to use will be

$A$ man can see up to $100 \, cm$ of the distant object. The power of the lens required to see far objects will be

The sensation of vision in the retina is carried to the brain by