Question

an electromagnetic radiation point source operates at a 250W power with a 10% efficiency. The average energy density at a point distant 10m from the source is​

Answer 1

Answer: 6.6 x 10^(-11)J/m^3

Explanation:

We know that intensity is given by the formula Power/Area.

Where,

Power= 250W

Area= 4x3.14x100= 1256 m^2

I= 250/1256

But

Intensity = Uc

Where U= Average Energy Density

And c= Speed of light

So U = I/c

= 6.6x10^(-11)J/m^3