Question

The powers of lenses used in the spectacles of a person are -2.5D and +2D respectively.State the focal length and nature of these lenses. ​

Answer 1

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• For concave lens Power is -ve
• P = 1/f
• f = 1/-2.5
• = -0.4m = -40cm
• For Convex Lens Power is +ve
• F = 1/2
• = 0.5m = 50cm