The sensation of vision in the retina is carried to the brain by

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

$A$ man suffering from short-sightedness (myopia) is unable to see objects distinctly at a distance greater than $2\,m$. The power of the lens required to correct this defect should be.......$D$

The light when enters the human eye experiences most of the refraction while passing through

$A$ student can distinctly see objects up to a distance of $15 \, cm$. He wants to see the blackboard at a distance of $3 \, m$. The focal length and power of the lens used,respectively,will be:

The ability of the eye to see objects at all distances is called