How Is the Speed of Light Calculated in Flint Glass?

[jimbo43]

Homework Statement

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

Homework Equations

Don't know where to start

The Attempt at a Solution

refractive index of 1.61
625 / w = 1.61
w = 625 / 1.61 = 388 nm.

 

[G01]

You know the index of refraction of the medium. This should be all you need to find the speed in the glass.

HINT: How does the speed of light in a material relate to the speed of light in a vacuum and the index of refraction?