# Two Lenses A And B Have Power of (I) +2d and (Ii) −4d Respectively. What is the Nature and Focal Length of Each Lens? - Science

Two lenses A and B have power of (i) +2D and (ii) −4D respectively. What is the nature and focal length of each lens?

#### Solution

Power of lens A = +2D
Power of lens B = -4D

Power =1/focal length

or  focal length= 1/power

Thus, focal length (fA ) of A =1/2=0.5m =50 cm

Focal length (f) of B = 1/-4=-0.25m=-25  cm

Therefore, lens A is a convex lens as it has a positive focal length and lens B is concave as it has a negative focal length.

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#### APPEARS IN

Lakhmir Singh Class 10 Physics (Science)
Chapter 5 Refraction of Light
Q 30.1 | Page 262