how do i do these questions?

Question 3 0 / 2 points The critical angle from a particular medium into air is 57. What is the index of refraction for this medium? (round answer to 2 decimal places) Answer: 0.84 x (1.19) Question 6 0 / 2 points The speed of violet light (7.51014 Hz) in deep water is 2.4x108 m/s and its angle from the incident ray to the boundary is 20 degrees. If its angle from the refractive ray to the boundary in shallow water is 30 degrees, the wavelength of the light in shallow water is abc nm? Record as abc. Answer: (468)