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

The image formed on the retina is:

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

$A$ person cannot see distinctly at a distance less than $1 \, m$. Calculate the power of the lens that he should use to read a book at a distance of $25 \, cm$.

The lens used to correct long-sightedness (hypermetropia) is:

Your friend is having an eyesight problem. She is not able to see a distant uniform window mesh clearly,and it appears to her as non-uniform and distorted. The doctor diagnosed the problem as: