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How and why does a prism split white light into the colour spectrum

  1. Oct 20, 2011 #1
    [Solved] How and why does a prism split white light into the colour spectrum

    1. The problem statement, all variables and given/known data

    How and why does a prism split white light into the colour spectrum?

    2. Relevant equations

    Red light has a lower frequency than violet light. As speed of light = wavelength * frequency, red light has a larger wavelength than violet light.

    3. The attempt at a solution
    For a prism to split the visible waves of varying wavelengths that collectively add up to form white light, the angles at which the waves are bent need to be different between the two extremes of red light and violet light.

    Where I'm stuck is, how and why is the angle of refraction different between red light waves and violet light waves?
     
    Last edited: Oct 20, 2011
  2. jcsd
  3. Oct 20, 2011 #2

    Borek

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    Staff: Mentor

    Light speed in the glass is a function of the wavelength.
     
  4. Oct 20, 2011 #3
  5. Oct 20, 2011 #4
    Keep in mind that this is purely an empirical relationship, i.e., you can measure a material's refractive index at various wavelengths and then find a set of "B"s and "C"s so that Sellmeier's equation makes a generally good fit. However, note that it predicts an infinite refractive index whenever the wavelength is equal to one of the "C"s. Check out "anomalous dispersion" for more info.
     
  6. Oct 20, 2011 #5

    Borek

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    Staff: Mentor

    Yes. Do you know how refractive index depends on the speed?

    Simplest answer: you find it experimentally.
     
  7. Oct 20, 2011 #6
    Snell's Law, n1/n2 = v1/v2, conveniently also = sin(o1)/sin(o2)
     
  8. Oct 20, 2011 #7

    Borek

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    Staff: Mentor

    So - for introductory physics - you know everything you need :smile:
     
  9. Oct 20, 2011 #8
    Good, thanks. :smile:
     
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