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:

When objects at different distances are seen by the eye,which of the following remains constant?

Myopia is due to

Myopia can be corrected with the help of a/an ...

$A$ 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 $25 \, cm$.