1. The problem statement, all variables and given/known data A beam of light, wavelength 625 nm in air, is incident on a block of flint glass at an angle of 31.5. Find: A) the speed of light in the flint glass 2. Relevant equations Don't know where to start 3. The attempt at a solution refractive index of 1.61 625 / w = 1.61 w = 625 / 1.61 = 388 nm.