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The power of a lens is +8D. What kind of lens is this?  (A) Convex (B) Concave (C) Concavo Convex (D) Convexo concave

Last updated date: 16th Jun 2024
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Hint Convex lenses are thin at the edges at budget at the middle whereas concave lenses are thin at the centre and budget at the sides. Power of a lens is positive for a convex lens because focal length of the convex lens is positive.

Complete step-by-step solution
Power of a lens is defined as the reciprocal of focal length in meters. Its unit is in Dioptre. Focal length of a convex lens is positive because it is a converging lens. As the power of a lens is reciprocal of the focal length, the convex lenses have positive power.

Therefore, the correct answer is A.

Note: We can find the focal length of this lens in m by doing a reciprocal of power which will give us focal length as 0.125 m or 12.5 cm. Power of the concave lens is negative as the focal length of the concave lens is negative. As power is the reciprocal of focal length the reciprocal of a negative focal length is again a negative value. Hence, a concave lens has negative power.