Question

Light rays move in straight lines. But through an optical fibre, they can move in any type of zig-zag path because

(a) the holes through the fibres are extremely fine

(b) light rays are absorbed at the entry end and relieved at the exit end of the fibre

(c) scattering of light occurs inside the fibre

(d) successive total internal reflections occur as a ray moves through the fibre

Answer 1

(d) successive total internal reflections occur as a ray moves through the fibre

The working of optical fibre is based on the phenomena of total internal reflection. Its inner part is core of higher refractive index surrounded by another layer of glass of lower refractive index. It is surrounded by plastic jacket.

When light enters from the one end of the core and moves towards cladding, then total internal reflection takes place again and again and light propagate through it. Optical fibres are used in decorative table lamps.