Question

A ray of light incident at ${49}^{c}irc$ on the face of an equilateral prism passes symmetrically. Calculate the refractive index of the material of the prism.

Answer 1

When rays passes symmetrically ,then rays is going to through minimum deviation.
Minimum deviation $\delta =2i-A$

An equilateral prism so, A is prism angle $A={60}^o$

For minimum angle the angle of refraction should be half of prism angle.

So $r=A/2={30}^o$

Now using the snell's law

$n_{air}sini=n_{glass}sinr$

$1\times sin49=n_{glass}sin30$

$n_{glass}=\frac{0.75}{0.5}$

$n_{glass}=1.51$