(a) For a ray of light travelling from a denser medium of refractive index `n_(1)` to a rarer medium of refractive index `n_(2)`, prove that `(n_(2))/(n_(1)) = sin i_(c)`, where `i_(c)` is the critical angle of incidence for the media.
(b) Explain with the help of a diagram, how the above principle is used for transmission of video signals using optical fibers.

Explanation

### Solution:

**(a)** To prove that \(\frac{n_2}{n_1} = \sin i_c\), where \(i_c\) is the critical angle of incidence for light traveling from a denser medium (refractive index \(n_1\)) to a rarer medium (refractive index \(n_2\)), we can use Snell's Law.

1. **Understanding Snell's Law**: Snell's Law states that:
\[ n_1 \sin i = n_2 \sin r \]
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