Question

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

• A. Half
• B. Double
• C. The same but a convex lens
• D. The same but a concave lens

Answer 1

The correct option is B Double

Focal length = $-$( Detected far point )

For curing myopia, a concave lens of focal length equal to the distance of the eye’s own far point is used. i.e. $f=-d$ Hence, if distance d is doubled, then the focal length will also be doubled.