https://doi.org/10.1351/goldbook.08584
Smallest angle of incidence at which total internal reflection occurs.
Note:
If \(n_{2}\) and \(n_{1}\) are the refractive indices, and \(n_{2} > n_{1}\), at the boundary, \(\sin \theta_{\rm{c}} = n_1/n_2\).
If \(n_{2}\) and \(n_{1}\) are the refractive indices, and \(n_{2} > n_{1}\), at the boundary, \(\sin \theta_{\rm{c}} = n_1/n_2\).