Question

Which one of the following is the working principle behind optical fibers?

• A. Reflection
• B. Refraction
• C. Diffraction
• D. Total internal reflection

Hint:

Optical fibers rely on repeated total internal reflection to transmit light signals efficiently over long distances with very low attenuation.

Answer 1

The Correct Option is D

Concept: Optical fibers work on the principle of total internal reflection (TIR). When light travels from a denser medium to a rarer medium and the angle of incidence exceeds the critical angle, it gets completely reflected back into the denser medium.

Step 1: Understanding light propagation in optical fibers.
An optical fiber consists of:
• Core (denser medium)
• Cladding (rarer medium) Light is guided through the core.

Step 2: Condition for total internal reflection.
Total internal reflection occurs when:
• Light travels from denser to rarer medium
• Angle of incidence $>$ critical angle

Step 3: Application in optical fiber.
Inside the fiber, light continuously undergoes total internal reflection at the core-cladding boundary, allowing it to travel long distances with minimal loss.

Step 4: Final conclusion.
Thus, the working principle of optical fibers is: \[ Total internal reflection \]