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# What is the phase velocity of light in glass? Watch

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

I have used eqn n=c/vp =λ0/λ

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.
2. (Original post by little pixie)
What is the phase velocity of light in glass if n=1.5 at λ=500nm?

I have used eqn n=c/vp =λ0/λ

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.
your answer is correct, you don't need the wavelength, it is only given as the refractive index can vary with wavelength (for example air is no longer transparent to high energy UV radiation)

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