What is the phase velocity of light in glass?

[ZedCar]

Homework Statement

What is the phase velocity of light in glass if n=1.5 at λ=500nm

Homework Equations

n=c/vp =λ0/λ

The Attempt at a Solution

1.5 = (3x10^8) / vp
vp = (3x10^8)/1.5

I'm not entirely sure if the equation I have used is the correct one. It does not use the λ=500nm as given in the question.

 

[mfb]

It is right, and you do not need the wavelength. In general, n will depend on the wavelength, but that is not relevant here.

 

[ZedCar]

Thanks mfb!