If the far point of a short-sighted person is $400 \ cm$, then the power of the lens required to enable him to see very distant objects clearly is

The near point and far point of a person are $40\,cm$ and $250\,cm$ respectively. Determine the power of the lens he/she should use while reading a book kept at a distance of $25\,cm$ from the eye $..........D$

$A$ person who can see things most clearly at a distance of $10 \, cm$ requires spectacles to enable him to see clearly things at a distance of $30 \, cm$. What should be the focal length of the spectacles?

Assertion : In a movie, ordinarily $24$ frames are projected per second from one end to the other of the complete film.
Reason : The image formed on the retina of the eye is sustained up to $1/10 \, s$ after the removal of the stimulus.

$A$ defective eye cannot see close objects clearly because their image is formed

$A$ 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 $25\, cm$?