Question

What is the power of concave lens?

• A. Positive
• B. Negative
• C. Neutral
• D. None

Answer 1

Answer: (B)

Negative

Correct answer (b)

Concave lens surfaces have a virtual and therefore negative radius of curvature. The convention signs used for focal length are also used for optical power. Convex lenses, which have a real focus, have a positive focal length and optical power. Concave lenses, with a virtual focus, have a negative focal length and optical power.