Question

Define power of a lens. A convex lens has a focal length of 10 cm. What is its

Power? Two thin lenses of focal length +10cm and -5cm are kept in contact. What

Is the focal length and power of the combinations?​

Answer 1

Answer:

The power of a lens is defined as the reciprocal of the focal length. Lens power is measured in dioptres (D). Converging (convex ) lenses have positive focal lengths, so they also have positive power values. Diverging (concave ) lenses have negative focal lengths, so they also have negative power values.

Explanation:

Focal length of the lens      f=10 cm =0.1 m

Power of lens     P=f1

∴   P=0.11=10  D