#### Question

Find the focal length of a lens of power -2.0 D. What type of lens is this?

#### Solution

Power of lens, *P*= 1/*f **P*= -2D*f*= -1/2 = -0.5 m

A concave lens has a negative focal length. Hence, it is a concave lens.

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Solution Find the focal length of a lens of power -2.0 D. What type of lens is this? Concept: Refraction at Spherical Surfaces and by Lenses - Power of a Lens.