1. Limited time only! Sign up for a free 30min personal tutor trial with Chegg Tutors
    Dismiss Notice
Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Homework Help: Plasma frequency, shield, laser

  1. Nov 28, 2013 #1
    1. The problem statement, all variables and given/known data
    A plasma is to be used as a shield against a laser in the visible spectrum (400 - 700 nm wavelength light) by attenuating the field amplitudes.

    (a) What is the minimum electron density that should be used?
    (b) What thickness of this shield would be needed to reduce the power of a 10 kW beam with wavelength 500 nm to below 1 W?

    2. Relevant equations
    omega p = √(Ne *e^2)/(me*epsilon0)

    Ne= electron density
    e= electron charge
    me= electron mass
    omega p = plasma frequencey

    V= Fλ

    V= velocity/speed of light
    F= frequency
    λ= wavelength

    3. The attempt at a solution

    For part a, is this the way to go about it?

    F=v/λ = 3x10^8 / 700nm = 4.29x10^14

    Ne= (omega p)^2 *me*epsilon0 / e^2 = 5.78 x10^-25

    Pretty stuck on what equations to use here

    any help much appreciated, thanks
  2. jcsd
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook

Can you offer guidance or do you also need help?
Draft saved Draft deleted