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Wavelength, Frequency, & Speed of Light in Different Media

  1. Nov 5, 2008 #1
    1. The problem statement, all variables and given/known data

    A beam of light from a monochromatic laser shines into a piece of glass. The glass has thickness L and index of refraction n=1.5. The wavelength of the laser light in vacuum is L/10 and its frequency is f. In this problem, neither the constant c nor its numerical value should appear in any of your answers

    How long does it take for a short pulse of light to travel from one end of the glass to the other?
    Express your answer in terms of some or all of the variables f and L. Use the numeric value given for in the introduction.

    2. Relevant equations

    c = [tex]\lambda[/tex] * f
    f = 1/t
    n = c/v

    3. The attempt at a solution

    t = 15/f

    i know this answer is correct, but I still cannot come up with how the correct answer was derived.
    Last edited: Nov 5, 2008
  2. jcsd
  3. Nov 5, 2008 #2


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    Science Advisor
    Homework Helper

    The speed in the glass is c/n = c/1.5
    The time through the glass is distance/speed = L / (c/1.5)
    Since you know c = [tex]\lambda[/tex] * f, you simple have to rearrange the equation subsituting for c.
  4. Nov 5, 2008 #3
    thanks you. i will begin working out the substitution.
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