Question

An electromagnetic wave strikes a 1.12-cm2 section of wall perpendicularly. the rms value of the wave's magnetic field is determined to be 5.50 Ã 10-4 t. how long does it take for the wave to deliver 2780 j of energy to the wall?

Answer 1

Answer:

0.34 s

Explanation:

We are given that

Area,A=$1.12 cm^2=1.12\times 10^{-4} m^2$

$1cm^2=10^{-4} m^2$

Magnetic field,B=$5.5\times 10^{-4} T$

Energy,E=2780 J

Intensity of electromagnetic wave which strikes the wall ,$I=\frac{B^2}{\mu_0}c$

Where $\mu_0=4\pi\times 10^{-7}$

$c=3\times 10^8 m/s$

$I=\frac{(5.5\times 10^{-4})^2}{4\pi\times 10^{-7}}\times 3\times 10^8$

$I=7.22\times 10^7W/m^2$

Average  power emitted by electromagnetic wave,$P_{avg}=IA=7.22\times 10^7\times 1.12\times 10^{-4}=8086.4 W$

Time,t=$\frac{E}{P_{avg}}$

$t=\frac{2780}{8086.4}=0.34 s$