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Homework Help: How does light travel in a vacuum?

  1. Apr 14, 2005 #1
    I have been doing a science fair project and I am going to the Canada-Wide-Science Fair this May to Vanouver, BC, and I have been trying to brush up on my project, and the question is, how does light travel in a vacuum, if the vacuum does not consist of anything, not even electrons, and I already know that light does not travel in waves

    Thanks in advance mates :)
  2. jcsd
  3. Apr 14, 2005 #2


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    Uhm... light does travel as waves. Light travels in photons which have wave and particle characteristics so they do not need a medium to travel through. Think you need to really do some large scale brushing up lol.
  4. Apr 14, 2005 #3
    Light is an electromagnetic wave. Only mechanical wave need a medium in order to travel... electromagnetic waves are particles moving at the speed of light due the combination of a electrical and a gravitational field. But in the case of light I'm really sure...
  5. Apr 15, 2005 #4


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    Hopefully you meant a magnetic field?

    Light can indeed propagate through a vacuum because it is electromagnetic in nature. It consists of electric and magnetic fields oscillating perpendicular to each other. That is the classical model, anyways, which is all I know.
  6. Apr 16, 2005 #5
    I am not sure about this classical model and its relevance to your situation, but in any event, yes I can once again affirm that these people are correct in that EM waves to not require a medium to propagate through. Just a little background on the fascinating theory of light...

    It used to be believed that there had to be a medium to propagate through and it was given the term "luminiferous aether," or the aether since at the time people only knew mechanical waves and could not understand a medium-less wave. The greatest American experimental physicist, Albert Michelson and his partner Edward Morley, attempted to prove the existence of the aether by using what is known as an interferometer. The way they intended to prove it existed was by splitting a beam with a 50% reflective mirror and "racing" the two light beams to a mirror and back. From there, they would create a new pattern that was either constructive or destructive that could be studied to determine which beam arrived sooner. If one made it back sooner, it would prove that there was a "wind" in the aether and thereby prove its existence and also provide a means of study. Unfortunately, the experiment did not come out the way they planned and to this day it is known as the greatest failure because of the detail and incredible experimental design that went into the amazing device. Their findings later were used to help prove there was no aether.

    Michelson is also responsible for the most famous speed of light experiments. He determined the speed of light down to the meter per second with less than one meter per second possible error back in the late nineteenth century. Today, we have modified it by adding three significant figures in the last two decades, but his original value is still accurate (although not as precise as our current value).
  7. Apr 16, 2005 #6
    The fact that light is a transverse wave and transverse waves do not need any medium for propogation is a lot more theoretical and qualitative fact.What this guy needs is the quantitative proof.

    This link would help:

    http://www.theory.caltech.edu/people/patricia/ltrav.html [Broken]
    Last edited by a moderator: May 2, 2017
  8. Apr 16, 2005 #7
    Yes sorry... I am a very distracted person.
  9. Apr 16, 2005 #8
    On the Toronto Regionals, a High-school physics teacher said that Light does not travel in waves, and he babbled a bunch about wave mechanics and stuff, and I got confused, and Im asking for help..

    So is there an easy and simple explanation on how light exactly travles in a vacuum?
  10. Apr 16, 2005 #9


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    The guy was wrong, plane and simple.

    Other people will help you better understand why though.
  11. Apr 16, 2005 #10
    I couldn't get to the link, but I highly doubt that it will explain why "transverse waves do not need any medium for propogation" because except for light, they do.
    Last edited by a moderator: May 2, 2017
  12. Apr 16, 2005 #11
    you may aslo want to look up the experiment by michelson-morley who did a test to see if light needed something to propogate threw. this was done like 100 years ago so the theroy behind it is not to indept if you search it on google you should be able to find more in an language that u can understand good luck with everything
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