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JEE Advanced2013PhysicsRay OpticsActual

The image of an object, formed by a plano - convex lens at a distance of 8 m behind the lens, is real and is one-third the size of the object. The wavelength of light inside the lens is 2 3 times the wavelength in free space. The radius of the curved surface of the lens is

Options

  1. A1 m
  2. B2 m
  3. C3 m
  4. D6 m

Correct answer

C. 3 m

Step-by-step solution

V = 8m Magnification = v u = - 1 3 u = -24 also μ = c V m = λ a λ m = 3 2 1 f = μ - 1 1 R 1 - 1 R 2 ​ 1 f = μ - 1 1 ∞ - 1 - R 1 f = 3 2 - 1 1 R f = 2R from lens formula 1 v - 1 u = 1 f 1 8 + 1 2 4 = 1 2R 4 24 = 1 2R ⇒ R = 3 m

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