Radiation intensity and distance, help?

Question

Sunlight falling on the upper layers of the Earth's atmosphere has an intensity of 1380 W/m2. If all the energy were carried by a single wave, (a) what would be the electric field amplitude Emax for this wave (V/m)? (b) What would be the magnetic field amplitude Bmax (T)?

Answer 1

The rate of energy transport per unit area is described by the Poynting vector S:

S = (1/mu ) (E X B) =1380 W/m2.

E(max)/B(max)= c = 3 x 10^8 m/s

Where mu = the magnetic permeability of vacuum

Two equations and two unknowns so solve for them.