A symmetric double convex lens in cut in two equal parts by a plane perpendicular to the principal axis. If the power of the original lens was 4 D, the power a cut-lens will be

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2 D The lens is cut into two equal parts by a plane perpendicular to the principal axis. Thus, the radius of curvature of both the lenses become half of its original value. As, f = R/2 P = 1/f Radius of curvature becomes half. Therefore, the focal also reduces to half its original value. Thus, the power (P) of the two cut-lenses will be equal. 2 P = 4 D P = 2 D

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