Question

A concave lens always gives a virtual image. In optical lenses worn by humans which of the following statements is true?

• A. The lens can never be concave
• B. In some cases the lens can be concave if the focal length is much larger than $25$cm
• C. All local length concave lenses are possible
• D. All focal length convex lenses are possible

Answer 1

The correct option is B In some cases the lens can be concave if the focal length is much larger than $25$cm

Corrective lens can both be convex and concave. Range of vision is from infinity to 25 cm for a normal person. Concave lens corrects short sightedness by making image of infinite object at far point. Since image should be formed at a greater distance than 25 cm , so focal length should be greater than 25 cm.
So In some cases the lens can be concave if the focal length is much larger than 25cm