Electromagnetic Waves, Energy, and Power

Preliminaries

ϵ0 = Quantity[1, "ElectricConstant"];
c = Quantity[1, "SpeedOfLight"];
μ0 = Quantity[1, "MagneticConstant"];

Savg[e_] := (1/2) ϵ0 c (e^2)

99.9 - The Hawk

The radio station broadcasts at 99.9 MHz with a power of 50,000 Watts.  What is the wavelength of the radio waves?  What are the maximum electric and magnetic fields at a distance of 1.25 kilometers from the station?  (Assume the power radiates evenly in all directions.)

f = Quantity[99.9, "MegaHertz"];

λ = c / f; UnitConvert[λ, "Meters"]

Use the 1/r^2 law to find the intensity.

P = Quantity[50000, "Watts"];
r = Quantity[1.25, "Kilometers"];

Intens = (P/(4 π (r^2))); UnitConvert[Intens, "Watts/Meter^2"]

Clear[e]
e = e /. Solve[Savg[e] == Intens && e > 0, e][[1]]

B = e/c ; UnitConvert[B, "Teslas"]

Laser Pointer

A 0.24 mW red laser pointer (λ = 655 nm) is focused onto a spot 3 cm^2 a distance 5.0 m away.  What is the frequency of the light wave?  What is the intensity of the laser?  What are the maximum values of the electric and magnetic field in the spot?

λ = Quantity[655., "Nanometers"];
f = c / λ; UnitConvert[f, "Hertz"]

A = Quantity[3.0, "Centimeters^2"]

P = Quantity[0.24, "Milliwatts"];

Intens = P/A; UnitConvert[Intens, "Watts/Meter^2"]

Clear[e]; e = e/. Solve[Savg[e] == Intens && e > 0, e][[1]]

B = e/c ; UnitConvert[B, "Teslas"]