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Difficulty: MediumPhysics Fundamentals and Everyday Applications

Optical fibers are widely used in modern telecommunication networks and medical endoscopy to transmit light signals across long distances with minimal loss of intensity. Which optical phenomenon is primarily responsible for guiding light through the core of an optical fiber?

  1. Total internal reflection at the core-cladding boundaryAnswer
  2. B
    Rayleigh scattering of light within the fiber core
  3. C
    Constructive interference between reflected light waves
  4. D
    Diffraction of light rays passing through the narrow core aperture

Answer

Total internal reflection at the core-cladding boundary
Optical fibers operate on the principle of total internal reflection. The inner core has a higher refractive index than the surrounding cladding. When light signals enter the fiber at an appropriate angle, they repeatedly strike the core-cladding interface at an angle greater than the critical angle, reflecting entirely within the core with negligible signal loss.

Step-by-Step Solution

1
Identify the structural composition of an optical fiber
An optical fiber consists of an inner core with a higher refractive index (n1n_1) surrounded by an outer cladding with a lower refractive index (n2n_2).
Light transmission requires light to travel from a denser medium toward a rarer medium.
2
Determine the conditions for total internal reflection
When light inside the core hits the core-cladding boundary at an angle of incidence greater than the critical angle (θc=arcsin⁡(n2/n1)\theta_c = \arcsin(n_2/n_1)), no light refracts into the cladding.
100% of the light energy is reflected back into the core, allowing high-efficiency propagation over long distances.

Key Concept

Total Internal Reflection in Optical Fibers
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Topics

Physics Fundamentals and Everyday Applications

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