Which of the following is true for the power of a concave lens?
Answer & explanation
Correct answer: option 2
The correct answer is Option (2) → The power of a concave lens is always negative
The power of a lens is P = 1/f, with f in metres, and its unit is the dioptre. A concave lens is a diverging lens and its focal length is negative under the sign convention, so its power is always negative. A convex lens has a positive focal length and a positive power.