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Homework Help: Force on a Lens

  1. Dec 5, 2008 #1
    1. The problem statement, all variables and given/known data
    A laser of power P with wavelength [tex]\lambda[/tex] is directed through a lens (focal length f) off the optical axis by a distance d. What is the sideways force on the lens?

    2. Relevant equations

    Not sure. The average radiation pressure is I/c, where I is the intensity. But this does not seem useful.
  2. jcsd
  3. Dec 5, 2008 #2


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    Science Advisor
    Homework Helper

    You can just think of this classicaly.
    Imaging a stream of particles being deflect downward by a certain angle - just calculate the resulting force on the deflector.

    The angle you get form the focal length - the number of particles (photons) from the intenisty and the momentum form the wavelength
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