Question

A spherically spreading EM wave comes from an 1800-W source. At a distance of 5.0 m, what is the intensity, and what is the rms value of the electric field?

Answer 1

Step-by-step explanation:

It is given that,

Power of EM waves, P = 1800 W

We need to find the intensity at a distance of 5 m. Also, the rms value of the electric field.

Intensity,

`I=(P)/(4\pi r^2)\\\\I=(1800)/(4\pi* (5)^2)\\\\I=5.72\ W/m^2`

The formula that is used to find the rms value of the electric field is as follows :

`I=\epsilon_o cE^2_(rms)`

c is speed of light and
`\epsilon_o` is permittivity of free space

So,

`E_(rms)=\sqrt{(I)/(\epsilon_o c)}\\\\E_(rms)=\sqrt{(5.72)/(8.85* 10^(-12)* 3* 10^8)}\\\\E_(rms)=46.41\ V/m`

Hence, this is the required solution.