dispersion and indices of refraction

[MDwannabe7]

So, if I understand this correctly, every material that light passes through has an intrinsic index of refraction, but per wavelength. In other words, while glass may have an index of refraction of 1.5 (say, for blue light), that is only for that (blue) wavelength of light, and may be 1.52 for a different (say, red) wavelength. This is known as dispersion and that's the gist of it, right? IF I do understand that correctly, then the longer wavelengths should have larger indexes of refraction, correct? (Based on n = c/v; longer wavelengths have slower velocities, right?)

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[BerkReviewTeach]

So, if I understand this correctly, every material that light passes through has an intrinsic index of refraction, but per wavelength. In other words, while glass may have an index of refraction of 1.5 (say, for blue light), that is only for that (blue) wavelength of light, and may be 1.52 for a different (say, red) wavelength. This is known as dispersion and that's the gist of it, right? IF I do understand that correctly, then the longer wavelengths should have larger indexes of refraction, correct? (Based on n = c/v; longer wavelengths have slower velocities, right?)

Right idea, but wrong final thought. Longer wavelengths "bend" less than shorter wavelengths, so red light has a lower index of refaction than blue light. Just recall the mnemonic, "Blue on bottom."

 

[Descarteo]

Right idea, but wrong final thought. Longer wavelengths "bend" less than shorter wavelengths, so red light has a lower index of refaction than blue light. Just recall the mnemonic, "Blue on bottom."

I understand the general concept, but wouldnt you expect longer wavelengths to have lower energies and thus be deflected more? Im a little confused on this one

 

[BerkReviewTeach]

I understand the general concept, but wouldnt you expect longer wavelengths to have lower energies and thus be deflected more? Im a little confused on this one

A good way to think about it is in terms of visualizing a transverse wave travelling through a thick medium. If it has a short wavelength, then it pushes up and down more through the medium than it would with a longer wavelength. This slows the wave down, meaning that a shorter wavelength correlates to a slower speed, and thus a greater index of refraction.