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Momentum of light

  1. Oct 26, 2014 #1
    Is the momentum of EM radiation due to the EM radiation applying a force on the electrons?
    Last edited: Oct 26, 2014
  2. jcsd
  3. Oct 26, 2014 #2


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  4. Oct 26, 2014 #3
    I don't think that's what I'm thinking of.

    I mean:
    Light is said to possess momentum. That means it can push things around right? So I'm asking is the reason light can push stuff around because EM wave pushes electrons?
  5. Oct 26, 2014 #4


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    Yes, that is the basic mechanism by which light (which is electromagnetic radiation) transfers energy and momentum to objects.

    But do note the word "basic" - entire books can be and have been written on the interaction of light and matter.
  6. Oct 26, 2014 #5
    Thanks, basic mechanism is all I wanted.
  7. Oct 26, 2014 #6
    But hold on, how does EM radiation push objects forward (such as in solar sails)? Isn't the force in EM radiation oscillating perpendicular to the direction of travel?
  8. Oct 26, 2014 #7


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    An electromagnetic wave has both an electrical and a magnetic component. Both fields are perpendicular to the direction of travel. However, the force exerted by these fields is not in general parallel to the field direction. (google for "Lorentz force").
  9. Oct 26, 2014 #8


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  10. Oct 26, 2014 #9
    Last edited by a moderator: Oct 26, 2014
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