If refractive indices for water and glass are $4/3$and $5/3$respectively and light is tending to go from glass to water, the critical angle is

Given that ${\mathrm{\mu }}_{\mathrm{w}}=4/3, {\mathrm{\mu }}_{\mathrm{g}}=5/3$

Light is travelling from glass to water then [$\because {\mathrm{\mu }}_{\mathrm{g}}={\mathrm{\mu }}_{\mathrm{w}}$we get critical angle]

$\frac{{\mathrm{\mu }}_{\mathrm{w}}}{{\mathrm{\mu }}_{\mathrm{g}}}=\frac{\sin \mathrm{c}}{\sin 90}$

${}_{\mathrm{w}}\mathrm{\mu }_{\mathrm{g}}=\frac{1}{\sin \mathrm{C}}$              glass – denser

$\frac{{\mathrm{\mu }}_{\mathrm{g}}}{{\mathrm{\mu }}_{\mathrm{w}}}=\frac{1}{\sin \mathrm{C}}$

$\frac{1}{\sin \mathrm{C}}=\frac{5}{4}\Rightarrow \sin \mathrm{C}=\frac{4}{5}$

$\mathrm{C}={\sin }^{-1}\left(\frac{4}{5}\right)$