CBSE Class 12-science Answered
how do optical fibres transmit light without absorption
Asked by gazanfarali5782 | 09 Jan, 2023, 03:21: PM
The optical fibre works on the principle of total internal reflection.
When light ray travels from a medium of high refractive index to another medium of low refractive
index, if the light ray incident on high refractive medium at an angle greater than particular angle which is called
critical angle only reflection will take place and no refraction of light into low refractive index medium .
This phenomenon is called total internal reflection(TIR)
The phenomenon of TIR is exploited to pass light through optical fiber.Light rays can be used to transmit
a huge amount of data, but light rays travel in straight lines. So unless we have a long straight cable made up of
transparent medium without any bends at all, transmitting light is very tedious.
Instead, the optical cables are designed such that they bend all the light rays inwards using TIR.

In optical fiber there is inner core and outer clad both are transparent to light.
Refractive index of core is greater than that of clad . Hence, light rays travel continuously,
bouncing off the optical fibre walls due to TIR and transmitting end to end data.
Although light signals degrade over progressing distances, depending on the purity of the material used,
the loss is much less than using metal cables.
Answered by Thiyagarajan K | 09 Jan, 2023, 04:49: PM
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