Question

A laser beam has intensity $2.5\times {10}^{14}W{m}^{-2}$. Find the amplitudes of electric and magnetic fields in the beam.

Answer 1

$C=\frac{E}{B}$

And $I=\frac{(E_{rms}{)}^2}{c{\mu }_o}$

or, $2.5\times {10}^{14}=\frac{(E_{rms}{)}^2}{3\times {10}^8\times 4\pi \times {10}^{-7}}$

$\therefore E_{rms}=30.7\times {10}^7$

Now, $E=\sqrt{2}\times E_{rms}$

$=\sqrt{2}\times 30.7\times {10}^7$

$=43.4\times {10}^{7}N{C}^{-1}$

$=4.34\times {10}^{8}N{C}^{-1}$

$\therefore B=\frac{E}{C}=\frac{4.34\times {10}^8}{3\times {10}^8}$

$B=1.44T$