Question

Find the power of a concave lens of focal length $2m$.

Answer 1

Step 1, Given data

Focal length $=-2m$ (It is concave lens)

Step 2: Formula used

Power of lens $=\frac{1}{focallength}$

Step 3: Finding the power

Power of the lens $=\frac{1}{-2}=-0.5D$

Hence the power of the lens is -0.5 D.