The drawing shows three materials, $a, b,$ and $c .$ A ray of light strikes the $a-b$ interface at an angle of incidence that just barely exceeds its critical angle. The reflected ray then strikes the $a-c$ interface at an angle of incidence that just barely exceeds its critical angle. Rank the three materials according to their indices of refraction, largest first.
Problem A ray of light is incident at the $a-b$ interface with an angle of incidence that just barely exceeds the critical angle of $\theta_{\mathrm{c}}=40.0^{\circ} .$ The index of refraction of material $a$ is $n_{a}=1.80 .$ Find the indices of refraction for the two other materials. Be sure your ranking of the indices is consistent with that determined in the Concept Question.