Question

Estimate the wavelength at which plasma reflection will occur for a metal having the density of electrons $N\approx 4\times {10}^{27}{m}^{-3}$. Take ${\epsilon }_0\approx {10}^{-11}\text{and}m\approx {10}^{-30},$ where these quantities are in proper SI units

• A. 200 nm
• B. 600 nm
• C. 800 nm
• D. 300 nm

Answer 1

The correct option is B 600 nm

$\lambda =\frac{2\pi c}{\omega }$

$=\frac{2\pi c}{\sqrt{\frac{N{e}^2}{m{\epsilon }_0}}}\approx 600nm$