Answer –
The incident, refracted and emergent rays associated with a glass prism ABC are shown in the given figure.
Angle of prism, therefore is A = $60°$
Refractive index of the prism is $\mu$= 1.524
$i_{1}$ is the Incident angle
$r_{1}$ is the Refracted angle
$r_{2}$ is the Angle of incidence at the face AC
e is the Emergent angle = $90°$
According to Snell’s law, for face AC, we can have:
$\frac{sin e}{sin r_{2}}=\mu$
$sin r_{2}=\frac{1}{\mu}\times sin\;90°$
=$\frac{1}{1.524}
= 0.6562$
Therefore $r_{2}=sin^{-1}0.6562=41°$
Therefore $r_{1}=A-r_{2}=60-41=19°$
It is clear from the figure that angle A=$r_{1}+r_{2}$
Using the Snell’s law, we have the relation:
$\mu=\frac{sin i_{1}}{sin r_{1}}$
$sin i_{1}=\mu sin r_{1}$
=$1.524\times sin 19°$=0.496
Therefore $i_{1}=29.75°$
Therefore, the angle of incidence is $29.75°$