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## 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