Question

Two lens have power (1)=+2d (2)-4d. what is the nature of focal length of each lens?

Answer 1

focal length 1=1/2 m = 50 cm     converging lens
focal length 2 =1/-4 m = -25 cm       diverging lens

Answer 2

(1). +2D indicates that the lens is converging lens(convex lens)

p=1/f.....where f in meter.....so focal length f=50cm

(ii). -4D indicates that the lens is diverging lens (concave lens)

similarly the focal length is -25 cm

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