A Light Beam Having a Wavelength Of $470 \mathrm {~nm}$ In Air Is Directed into Glycerine at an Angle Of In Air

A light beam having a wavelength of $470 \mathrm {~nm}$ in air is directed into glycerine at an angle of $75.0 ^ { \circ }$ with the normal in air. Glycerine has a refractive index of $1.47 . \left( c = 3.0 \times 10 ^ { 8 } \mathrm {~m} / \mathrm { s } \right)$
(a) What are the frequency and wavelength of the light in the glycerine?
(b) What angle does the light beam make with the normal in the glycerine?