Question

The refractive index of the core of an optical fiber is ${\mu }_2$ and that of the cladding is ${\mu }_1$. The angle of incidence on the face of the core so that the light ray just undergoes total internal reflection at the cladding is

• A. $si{n}^{-1}\left(\frac{{\mu }_1}{{\mu }_2}\right)$
• B. $si{n}^{-1}({\mu }_2-{\mu }_1)$
• C. $si{n}^{-1}\left(\sqrt{{\mu }_2^2-{\mu }_1^2}\right)$
• D. $si{n}^{-1}\left(\sqrt{{\mu }_1^2-{\mu }_2^2}\right)$

Answer 1

The correct option is C $si{n}^{-1}\left(\sqrt{{\mu }_2^2-{\mu }_1^2}\right)$

$i=si{n}^{-1}\left[\sqrt{{\mu }_2^2-{\mu }_1^2}\right]$