Question

A microwave oven operates at 2.4 GHz with an intensity inside the oven of 2800 W/m2 .Part A What is the amplitude of the oscillating electric field? Part B What is the amplitude of the oscillating magnetic field?

Answer 1

Definition of Intensity: I = P/A
For an electromagnetic wave the electric field amplitudeis E­_o, and magnetic field amplitude is B₀

I = (1/2)xCxℰ₀x(E₀)² = (1/2)x (C/μ₀)x(B₀)²

Therefore starting with Part B:
I = (1/2)x(C/μ₀)x(B₀)²
(B₀)² = (2μI)/C
(B₀)² = (2x(4πx10^-7)x2800]/(3x10⁸)
(B₀)² = 2.3445x10^-11
Hence, B₀ = √(2.3445x10^-11)

                = 4.8x10^-6 T

Then for Part A:
E₀ = CxB₀
E₀ = (3x10⁸) x (4.8x10^-6)
Therefore, E₀ = 1440 V/m