Fundamentals of Physics Extended (10th Edition)

Published by Wiley
ISBN 10: 1-11823-072-8
ISBN 13: 978-1-11823-072-5

Chapter 33 - Electromagnetic Waves - Problems - Page 1001: 17b



Work Step by Step

The average intensity of electromagnetic radiation is equal to the average value of the Poynting vector, which is equal to $$S=\frac{E_mB_m}{2\mu_o}$$ Using the fact that $B_m=\frac{E_m}{c}$, the formula becomes $$S=\frac{E_m^2}{2\mu_o c}$$ Substituting known values of $E_m=2.0V/m$, $\mu_o=4\pi \times 10^{-7} H/m$, and $c=3.00\times 10^8m/s$ yields an average intensity of $$S=\frac{(2.0V/m)^2}{2(4\pi \times 10^{-7}H/m)(3.00\times 10^8m/s)}=0.0053W/m^2$$
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