Question

At some instant and location, the electric field associated with an electromagnetic wave in vacuum has the strength 98.5 V/m. Find the magnetic field strength, the energy density, and the power flow per unit area, all at the same instant and location.

Answer 1

Answer:

$B = 3.28 \times 10^{-7} T$

$u_{density} = 4.3 \times 10^{-8} J/m^3$

$Intensity = 12.88 W/m^2$

Explanation:

As we know that the electric field strength in vacuum due to electromagnetic waves is given as

$E = 98.5 V/m$

now we know the relation between electric field and magnetic field as

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

$B = \frac{98.5}{3\times 10^8}$

$B = 3.28 \times 10^{-7} T$

For energy density we know that

$u_{density} = \frac{1}{2}\epsilon_0 E^2$

$u_{density} = \frac{1}{2}(8.85 \times 10^{-12})(98.5)^2$

$u_{density} = 4.3 \times 10^{-8} J/m^3$

Power flow per unit area is given as

$Intensity = energy density \times speed$

$Intensity = (4.3 \times 10^{-8})(3\times 10^8)$

$Intensity = 12.88 W/m^2$