A plano-convex lens of unknown material and unknown focal length is given. With the help of a spherometer we can measure the, (a) refractive index of the material (b) focal length of the lens (c) radius of curvature of the curved surface (d) aperture of the lens

Answer: (c). A spherometer measures the sagitta h of a curved surface; with leg distance l, R = l²/6h + h/2. It gives only the radius of curvature, not μ or f (those need more data). So the answer is (c) radius of curvature of the curved surface.

A plano-convex lens of unknown material and unknown focal length is… | NEET 2020 (Phase 2)

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Spherical Surfaces & Thin Lenses

A plano-convex lens of unknown material and unknown focal length is given. With the help of a spherometer we can measure the,

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Answer: (c)

A spherometer measures the sagitta $h$ of a curved surface; with leg distance $l$ , $R = \frac{l^2}{6h} + \frac{h}{2}$ .
It gives only the radius of curvature, not $\mu$ or $f$ (those need more data).
So the answer is (c) radius of curvature of the curved surface.

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