RAS question
Optical fibre communication uses which principle?
Correct answer: (A) Total internal reflection.
Optical fibre communication uses total internal reflection to guide light signals through the fibre core over long distances with low loss.
Explanation
Optical fibre communication works on total internal reflection, not on ordinary bending of light alone. Light enters a high-refractive-index core and is repeatedly reflected at the core-cladding boundary, allowing the signal to remain confined inside the fibre. CBSE Academic, Class XII Physics Sample Question Paper 2023-24 supports the key point: propagation of light through an optical fibre is due to total internal reflection at the core-cladding interface. This is why optical fibres can carry light signals over long distances with minimal loss. Optical fibres also have practical advantages: high bandwidth, low loss, and immunity to electromagnetic interference, which make them suitable for modern communication links.
Why the other options are wrong
- (B) Refraction alone bends light at an interface, but by itself it does not keep the signal confined inside the optical fibre core.
- (C) Diffraction refers to the spreading of light, whereas optical fibre communication depends on repeated reflection at the core-cladding boundary.
- (D) Polarization concerns the direction of vibration of a light wave, not the principle that guides light through an optical fibre.
Concept
This tests the ray-optics concept of total internal reflection in a technology application. It recurs in RAS because optical fibre communication links basic physics with everyday science and technology infrastructure.