Two light rays A and B travel from a medium into air at angles of incidence 15 degrees and 42 degrees respectively. In the medium, light travels 3 cm in 0.2 ns . Will there be total internal reflection? If so, which ray?

Step-by-step solution

The speed of light in the medium is v = d t = 3 10⁻² m 0.2 10⁻⁹ s = 1.5 10⁸ m/s . The refractive index of the medium is n = c v = 3 10⁸ 1.5 10⁸ = 2 . The critical angle _ c is given by ( _ c ) = n_ air n_ medium = 1 2 . Thus, _ c = 30^ . Total internal reflection occurs when the angle of incidence i > _ c . For ray A, i_ A = 15^ For ray B, i_ B = 42^ > 30^ , so total internal reflection occurs for ray B. Answer: Yes, B