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Homework Help: Properties of light?

  1. Sep 10, 2010 #1
    1. The problem statement, all variables and given/known data

    i have read in my 7th grade text book, "LIGHT TRAVELS IN STRAIGHT LINE". But in my 12th grade text book, it has been mentioned " Light is an electromagnetic wave and transverse in nature". Transverse means the vibrations are perpendicular to the direction of propagation. Which is true? If light is a transverse wave, then it will have crest and trough which is not straight lines, but curves. Could u please elaborate me, revered members?

    2. Relevant equations

    3. The attempt at a solution
  2. jcsd
  3. Sep 10, 2010 #2


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    Staff: Mentor

    (Thread moved from Advanced to Intro Physics)

    Think of the transverse wave like travelling waves on a string. If you have a long straight string, and pluck the near end, that sends a transverse impulse down the string. If you drive the near end with a sinusoidal sideways displacement, that sends a travelling wave dow the string. The fact that the displacements of the string are orthogonal to the direction of travel doesn't alter the fact that the travelling wave propagates in a straight line down the string.
  4. Sep 11, 2010 #3


    Staff: Mentor

    When a wave is called transverse that simply means that it can be polarized, it does not mean that it actually moves in a transverse direction.

    Waves on a string as berkeman mentioned may be polarized: you can wiggle the string up and down or you can wiggle it left and right. They also consist of material physically moving in the transverse directions.

    EM waves may also be polarized: the E-field may point vertically or the E-field may point horizontally. However, there is no material physically moving vertically or horizontally.
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