$A$ man is suffering from colour blindness for green colour. To remove this defect,he should use goggles of

If the distance of the far point for a myopia patient is doubled,the focal length of the lens required to cure it will become

The substance present in the choroid is:

$A$ person has been using spectacles of power $-1.0$ diopter for distant vision and a separate reading glass of power $+2.0$ diopters. What is the least distance of distinct vision for this person in $cm$?

Hypermetropia is a:

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