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Can someone help me understand the (basic) physics behind white dispersion in prisms?

  • Thread starter Elbobo
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  • #1
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Not really a homework question, but I don't understand the concept. How do I know when the light bends upward or downward? How do I know qualitatively how much the red and violet lights disperse apart?

I know it has something to do with Snell's law, but I can't seem to get the necessary equations to predict what happens. My teacher hasn't explained it, nor does my book.
 

Answers and Replies

  • #2
tiny-tim
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How do I know when the light bends upward or downward?
Light always is nearer the perpendicular in the denser medium.
How do I know qualitatively how much the red and violet lights disperse apart?
It depends on the speed of red and violet light …

cacluating those speeds is way too difficult for your course :wink:
 
  • #3
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Oooh, ok I understand the answer to my first question now, thanks :)

On the 2nd part, I figured as much, but I'm not trying to calculate exact speeds. For example, if I were to compare the dispersion of colors in Air-Prism vs. Water-Prism, how do I determine if the colors expand or contract? That's where I tried to find a formula combining wavelength and index of refraction, only to get confused and wind up here. =/
 

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