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Geometrical Optics question

2002 · Shift 0 · Q132
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Geometrical Optics question

2002 · Shift 0 · Q132

JEE MainPhysicsGeometrical OpticsMCQ+4 / −1
Which of the following is used in optical fibres?
  1. A
    total internal reflection
  2. B
    scattering
  3. C
    diffracttion
  4. D
    refraction
View written solutionFree

Correct answer: A

  1. Principle of optical fibre

    Optical fibres guide light through a long thin transparent medium.

  2. Working mechanism

    In an optical fibre, light travels inside the core and keeps reflecting from the core-cladding boundary.

    This happens when the light goes from a denser medium to a rarer medium at an angle greater than the critical angle.

    The phenomenon is called total internal reflection.

  3. Check the options

    • A: total internal reflection — Correct. This is the basic principle used in optical fibres.
    • B: scattering — Incorrect. Scattering spreads light in different directions and is not the guiding principle.
    • C: diffraction — Incorrect. Diffraction is bending of light around obstacles/openings, not the main mechanism here.
    • D: refraction — Incorrect. Refraction occurs at interfaces, but optical fibre operation mainly depends on repeated total internal reflection.

  4. Derived answer

    Therefore, the correct option is:

    A: total internal reflection\boxed{\text{A: total internal reflection}}A: total internal reflection​

  5. Comparison with stored answer

    Stored correct answer: A

    Our derived answer: A

    Hence, they agree.

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