A lens is a transparent medium bounded by two surfaces, with one or both surfaces being…
Physics · Class 12 · CBSE — Ray Optics & Optical Instruments
A lens is a transparent medium bounded by two surfaces, with one or both surfaces being spherical. The focal length of a lens is determined by the radii of curvature of its two surfaces and the refractive index of its medium with respect to that of the surrounding medium. The power of a lens is reciprocal of its focal length. If a number of lenses are kept in contact, the power of the combination is the algebraic sum of the powers of the individual lenses.
A double-convex lens, with each face having same radius of curvature R, is made of glass of refractive index n. Its power is:
- \(\frac{2(n-1)}{R}\)
- \(\frac{(2n-1)}{R}\)
- \(\frac{(n-1)}{2R}\)
- \(\frac{(2n-1)}{2R}\)
Answer
(A) 2(n-1) R
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