Question

An electromagnetic wave with frequency 65.0hz travels in an insulating magnetic material that has dielectric constant 3.64 and relative permeability 5.18 at this frequency. the electric field has amplitude 7.20×10−3v/m.what is the intensity of the wave in a medium\?

Answer 1

Ans: Intensity = I = $5.8 * 10^{-8} W/m^2$

Explanation:
First you need to find out the speed of Electromagnetic wave:

Since
v = $\sqrt{ \frac{1}{\mu\epsilon} }$


v = $\sqrt{ \frac{1}{\mu_r\mu_ok\epsilon_o} }$
$\mu_r = 5.18 \\ \mu_o = 4 \pi * 10^{-7} \\ k = 3.64 \\ \epsilon_o = 8.85 * 10^{-12}$

Plug in the values:
v = $\sqrt{ \frac{1}{(5.18)(4\pi*10^{-7})(3.64)(8.85*10^{-12})} }$
v = $6.9 * 10^7$ m/s

Now that we have "v", we can use the following formula to find the intensity of wave:

$I = \frac{k\epsilon_o*v*E_{max}^2}{2}$

$I = \frac{(3.64)(8.85*10^{-12}) *(6.9*10^7)*(7.20*10^{-3})^2}{2}$

Intensity = I = $5.8 * 10^{-8} W/m^2$