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Plasma frequency, shield, laser

  • #1

Homework Statement


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?


Homework 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



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

(b)
Pretty stuck on what equations to use here

any help much appreciated, thanks
 

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