Question

The intensity of the sunlight reaching the earth is $1.380W{m}^{-2}$ Assume this light to be a plane, monochromatic wave. Find the amplitudes of electric and magnetic fields in this wave

Answer 1

We know, Intensity of wave
$=\frac{1}{2}{ϵ}_0{E}_0^{2}c$
Here, ${ϵ}_0=8.85\times {10}^{-12},E_0=?,C=3\times {10}^8,I=1380w/m^2$
Then $1380=\frac{1}{2}\times 8.85\times {10}^{-12}\times E_0^2\times 3\times {10}^8\Rightarrow E_0^2=\frac{2\times 1380}{8.83\times 3\times {10}^{-4}}=103.95\times {10}^4{E}_0=10.195\times {10}^2=1.02\times {10}^{3}Since{E}_0=B_{0}C{B}_0=\frac{E_0}{C}=\frac{1.02\times {10}^2}{3\times {10}^{28}}=3.398\times {10}^{-6}=3.4\times {10}^{-6}T$