Monochromatic Light Frequency in Glass (5.20 x 10^2 nm, n=1.50)

[_Ankoku_]

Homework Statement

Monochromatic light of a wavelength of 5.20 x 10^2 nm enters glass (n=1.50). What is the frequency of light in the glass?

Homework Equations

I am thinking I am supposed to use the formula : wave length = d(sin ( ) )/n
and then v=Frequency(wave length)

The Attempt at a Solution

This is where i got lost...

I attempted to use the formulas but got really confused.

 

[Dick]

Forget the formulas. What's the frequency outside of the glass? Can the frequency inside of the glass be different? Frequency counts the number of waves passing per second. If the number outside and inside are different, where are the extra waves going?? This may be more of an understanding question than a formula question.