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NEET2026PhysicsChapterActual

Optical fibers are extensively used for transmitting audio and video signals over long distances without significant loss of intensity. Which of the following statements correctly describes the design principle and the optical phenomenon responsible for guiding light inside the fiber?

Options

  1. AThe core must have a higher refractive index than the cladding, and light is guided by successive refractions.
  2. BThe core must have a lower refractive index than the cladding, and light is guided by total internal reflectio
  3. CThe core must have a higher refractive index than the cladding, and light is guided by total internal reflecti
  4. DThe core must have a lower refractive index than the cladding, and light is guided by successive refractions.

Correct answer

C. The core must have a higher refractive index than the cladding, and light is guided by total internal reflecti

Step-by-step solution

Optical fibers operate on the principle of total internal reflection. For total internal reflection to occur, light must travel from an optically denser medium to an optically rarer medium, and the angle of incidence must be greater than the critical angle. Therefore, the core of the optical fiber must have a higher refractive index than the surrounding cladding. Answer: The core must have a higher refractive index than the cladding, and light is guided by total internal reflection.

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