What is the relation between the refractive index of core n1 and cladding n2?

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ALP CBT 2 Electronic Mechanic Previous Paper: Held on 21 Jan 2019 Shift 1
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  1. n2 is less than n1
  2. n1 is equal to n2
  3. n1 is less than n2
  4. No relation between n1 and n2

Answer (Detailed Solution Below)

Option 1 : n2 is less than n1
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  • Optical fibers are cylindrical solid glass material acting as waveguides made of two concentric layers of very pure glass.
  • The core (the interior layer) with refractive index n1 serves as the medium for light propagation, while the cladding (the exterior layer) has a lower refractive index n2 where n1 > n2 assuring that light rays are reflected the core.
  • Since the cladding does not absorb any light from the core, the light wave can travel great distances.

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Explanation:

  • The working principle of optical fibers is Total Internal Reflection.
  • Optical fiber mostly used for communication purposes with negligible loss of energy.
  • The “Total Internal Reflection” of light is the boundary between transparent media of two different refractive indices.
  • At present, Optical fiber cables are used for communication like sending images, voice messages, etc.
  • The designing of this cable is done with Plastic or glass so that data can be transmitted effectively and quickly than other modes of communications
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