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The glass of optical fibre has a refractive index 1 . 55 and cladding with another glass of refractive index 1 . 51 . When the surrounding medium is air, the numerical aperture will be

Options

  1. A0 . 625
  2. B0 . 350
  3. C0 . 528
  4. D0 . 704

Correct answer

B. 0 . 350

Step-by-step solution

For air, μ 0 = 1 . Here, μ 1 = 1.55 , μ 2 = 1.51 N A = μ 1 2 - μ 2 2 μ 0 = 1.55 2 - 1.51 2 1 = 0.350

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