19.13) When light enters a medium of refractive index 1.4 from a medium of refractive index 2, for which of the following angle of incidence would

19.13) When light enters a medium of refractive index 1.4 from a medium of refractive index 2, for which of the following angle of incidence would total internal reflection take place?

**** The answer is47.95° but I need to know how (step-by-step, all formulas written out)****