Question

Find the focal length of a lens of power -2d. Identify the type of lens

Answer 1

Power = 1/Focal length
Focal length = -1/2 m = -0.5 metres = -50 centimetres
So, this Lens is a concave lens, i.e a diverging lens because the focal length is negative.

Hope this helps you !

Answer 2

Answer:

f=-50cm

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