physics
posted by jay .
The electromagnetic wave that delivers a cellular phone call to a car has a magnetic field with an rms value of 1.90 1010 T. The wave passes perpendicularly through an open window, the area of which is 0.20 m2. How much energy does this wave carry through the window during a 35s phone call?

Multiply the Poynting flux vector S by the window area and the 35 s time interval.
You will need an electromagnetism textbook to relate the Poynting (energy) flux to the rms B field. S is proportional to the square of the B field.
S (W/m^2) = 2*[10^7 c/(8 pi)]*Brms(T)^2
If B = 1.9*10^10 T, the electromegnetic flux is
S = 2.38*10^14*Brms^2
= 8.6*10^6 W/m^2
Energy = 6.02*10^5 W