Wavelength / index of refraction

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mspeedwagon

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Have a question that seems like it should be very simple, but can't get the right answer.

Light has a wavelength of 600 nm in vacuum. It passes into glass, which has an index of refraction of 1.50. What is the wavelength of the light in the glass?

Thanks!

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400nm

c/n=v therefore nv=c(a constant) therefore n1v1=n2v2

v=frequency*wavelength therefore n1*frequency*wavelength1=n2*frequency*wavelength2 (recall frequency is not changed when light passes into a new medium)

therefore n1*wavelength1=n2*wavelength2

wavelength2=n1*wavelength1/n2=1*600nm/1.5=400nm
 
Perfect. Thanks!

400nm

c/n=v therefore nv=c(a constant) therefore n1v1=n2v2

v=frequency*wavelength therefore n1*frequency*wavelength1=n2*frequency*wavelength2 (recall frequency is not changed when light passes into a new medium)

therefore n1*wavelength1=n2*wavelength2

wavelength2=n1*wavelength1/n2=1*600nm/1.5=400nm
 
Perfect. Thanks!

If you think about it conceptually, the light slows down when it hits the glass due to its higher index of refraction. Since the frequency is constant (its coming from the same source), the wavelength must decrease (V=F*L). Since the index of reaction is increased by a factor of 1.5, the wavelength must decrease by a factor of 1.5
 
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