The magnitude of focal length of a concave lens is 2 m. What is the power of the lens?
[amp_mcq option1=”+0.5 dioptre” option2=”-0.5 dioptre” option3=”+2.0 dioptre” option4=”-1.0 dioptre” correct=”option2″]
This question was previously asked in
UPSC CAPF – 2022
The formula is P = 1/f.
For a concave lens, the focal length is conventionally considered negative.
Given the magnitude of the focal length of the concave lens is 2 m, the focal length f = -2 m.
Power P = 1 / (-2 m) = -0.5 m⁻¹ = -0.5 dioptre (D).