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Homework Help: Wavelength of light in water

  1. Dec 8, 2008 #1
    1. The problem statement, all variables and given/known data

    "Light of wavelength 0.527 µm (in air) enters the water in a swimming pool. The speed of light in water is 0.700 times the speed in air. What is the wavelength of the light in water?"


    2. Relevant equations

    v = c /n, where n = 1.33 ,the index of refraction

    3. The attempt at a solution

    The wavelength of light in air is given. [tex]\lambda[/tex]=0.527
    I looked up the speed of light in air -- 299704644.54 m/s
    I also know that the speed of light in water is 0.700(299704644.54)

    I am not sure how to relate these numbers to v = c/n though, or the equation to use to find the [tex]\lambda[/tex] of light in water. Can anyone offer any insight? Thanks!
     
  2. jcsd
  3. Dec 8, 2008 #2

    Doc Al

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    Staff: Mentor

    What's the relationship between speed, wavelength, and frequency for any wave? Which of those parameters remains unchanged when light travels from one medium to another?
     
  4. Dec 8, 2008 #3
    frequency = v / [tex]\lambda[/tex], so I would think the frequency would be left unchanged.

    So I'm thinking I could do:

    f = (speed of light in air)/0.527

    to solve for the frequency, then use that value to solve for the wavelength of light in water?
     
  5. Dec 8, 2008 #4

    Doc Al

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    Staff: Mentor

    Good.

    OK, but even easier is to realize that the ratio v/λ must remain fixed, so λ decreases by the same factor that the speed decreases.
     
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