Understanding Snell's Law: How to Know When Light Bends

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Elbobo
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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.
 
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Elbobo said:
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:
 


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. =/