refraction help

[wikidrox]

Here is the question:
Violet light has a frequency of 7.5 * 10^14 hz and travels from air to glass at an angle of 30 degrees. The index of refraction for violet light is 1.54.
A) Find the angle of refraction
B) Find the wavelength in air
C) Find the wavelength in glass
D) What is the speed of propogation in glass.

I was able to find the angle of refraction to be 19 degrees. But now I don't know how to find the wavelengths in each of the mediums. Can someone help me?

[Doc Al]

Apply the wave equation: V = f*λ, where V is the speed of light in the medium. Realize that the speed of light in glass is slower than in air by a factor equal to the index of refraction. The frequency of light remains unchanged as it passes from air to glass.