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

$A$ 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 $25\, cm$?

Myopia is a defect of the eye due to which a person experiences difficulty in seeing .......

$A$ man can see only between $75 \, cm$ and $100 \, cm$. The power of the lens required to correct the near point will be:

$A$ student studying the similarities and differences between a camera and the human eye makes the following observations:
$I$. Both the eye and the camera have convex lenses.
$II$. In order to focus,the eye lens expands or contracts while the camera lens moves forward or backward.
$III$. The camera lens produces upside down real images while the eye lens produces only upright real images.
$IV$. $A$ screen in a camera is equivalent to the retina in the eyes.
$V$. $A$ camera adjusts the amount of light entering in it by adjusting the aperture of the lens. In the eye,the cornea controls the amount of light. Which of the above statements are correct?

$A$ man who cannot see clearly beyond $5 \, m$ wants to see stars clearly. He should use a lens of focal length ....... $m$.