CONCEPT ∘
Total Internal reflection: The total reflection of light from a higher refractive index medium to back in its medium at an angle more than a critical angle known as total internal reflection.
∘ It always happens when light travels from denser medium to rarer medium.
∘At critical angle
it makes 90° angles with normal separating two media.
Sin
=
[where
= rarer medium,
= denser medium]
∘Optical fibre: ∘ It is a very thin fibre made of glass and plastic having a radius of the order of a micrometre (10-6 m).It works on the
principle of Total Internal Reflection. ∘It is lightweight, fast, and useful for long-distance data and light transmission with very few losses.
∘A bundle of such thin fibres forms a light pipe.
Refraction: When a ray of light passes from
one medium to another it suffers a
change in direction at the boundary of two media is called refraction.
∘The change in direction because the speed of light travels at different speeds in different mediums.
∘Refractive Index of a medium defines that it is denser or rarer
∘
Refractive Index = Speed of light in Vacuum /speed of light in that medium. Refractive Index = η = c/v where, c = Speed of light in Vacuum, v= speed of light in that medium.
∘
Dispersion of light: The splitting of white light when it passes through a glass prism into its constituent spectrum of colours.
∘The constituents of white light are Violet, Indigo, Blue, Green, Yellow, Orange and Red. i.e. seven colours (VIBGYOR)
EXPLANATION ∘As explained above, the optical fibre works on the principle of Total Internal Reflection (TIR) for high-speed data transfer.
∴
Option 2 is correct.