Astigmatism (for a human eye) can be removed by using

The far point of a myopic eye is $250 \, cm$. What is the focal length of the lens required to correct this defect?

The impact of an image on the retina remains for......$sec$.

$A$ far-sighted person has a near point of $60\, cm$. What power lens should be used for eyeglasses such that the person can read a book at a distance of $25\, cm$?

$A$ person cannot see objects clearly beyond $2.0 \, m$. The power of the lens required to correct his vision will be:

$A$ person cannot see objects clearly beyond a distance of $40 \, cm$. What power of lens should be prescribed for them?