Index of refraction related to wavelength & frequency

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  • #1
I'm going through the Light & Optics chapter of Kaplan MCAT prep material & am having a hard time conceptually understanding the relationship between index of refraction & wavelength or with frequency.

It says in the book that n = c/v, & "when the speed of the light wave varies with wavelength, a material exhibits dispersion", then goes on to describe white light dispersion by a prism. Here is where I get confused, it continues to state that "violet light 'sees' a greater index of refraction than red does & so is bent to a greater extent"

The book also clearly indicates that larger f = smaller λ = larger n = more bending (e.g. for violet light relative to red). How is that so? Considering that v = fλ, smaller λ corresponds to smaller v & so by n = c/v it also corresponds to larger n & more bending, but shouldn't larger f = larger v = smaller n??

Any help would be appreciated! :)

Answers and Replies

  • #2
This is a good question. The frequency of the light doesn't actually change when the light crosses a boundary, only the wavelength does. Thus n = c/v = c/(fλ) and is thus inversely proportional to the wavelength.
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