Question

Refractive index of glass is 1.5. Find the speed of light in glass, if its speed in air is $3\times {10}^{8}m{s}^{-1}$. Also find critical angle for glass.

Answer 1

we know that refractive index $n=\frac{speedoflightinvacuum}{speedoflightinmedium}$

where $c=3\times {10}^{8}m/s$

$1.5=\frac{c}{v}$

$v=\frac{3\times {10}^8}{1.5}$

$v=2\times {10}^{8}m/s$

For critical angle we will use snell's law

C is critical angle

$n_{glass}sinC=n_{air}sin90$ $n_{air}=1$

$sinC=\frac{1}{n_{glass}}=\frac{1}{1.5}$

$C={41.8}^o$