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Electromagnetic Waves (concept)

  1. Sep 22, 2009 #1
    1. The problem statement, all variables and given/known data
    Given the electromagnetic wave traveling in the y direction at velocity c:

    B = +cEo sin(k y − ω t) ˆi.

    a) What happens to the ratio of the electric to magnetic field if the angular velocity ω of the
    wave is decreased? Does it decrease, increase, or remain the same?

    b) What happens to the velocity of the wave if the angular velocity ω of the wave is decreased? Does the velocity decrease, increase, or remain the same?

    c) What happens to the the wavelength of the wave if the angular velocity ω of the wave is
    decreased? Does the wavelength decrease, increase, or remain the same?

    2. Relevant equations

    E/B = v
    v= ω/k
    λ/c = 2*π/ω

    3. The attempt at a solution

    a) My guess: Since v= ω/k, decreasing ω would decrease v. So, if E/B = v, and v is decreasing, E/B also decreases. I think the ratio decreases. (INCORRECT)

    b) My guess: Since v=ω/k, velocity decreases as ω decreases. I think the velocity decreases.

    c) My guess: Wavelength is inversely related to angular velocity by λ/c = 2*π/ω. So, if angular velocity decreases, the wavelength increases. I think the wavelength increases.
     
  2. jcsd
  3. Sep 22, 2009 #2

    kuruman

    User Avatar
    Science Advisor
    Homework Helper
    Gold Member

    All electromagnetic waves in vacuum travel at the speed of light c regardless of their frequency or wavelength. Start from there and reconsider your answers.
     
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