Question

The power of a wave having an electric field strength of 12.8 units is

(a) 0.217

(b) 0.721

(c) 0.127

(d) 0.172

I have been asked this question during a job interview.

This intriguing question originated from Transients in chapter Waveguides of Electromagnetic Theory

Answer 1

Correct answer is (a) 0.217

Best explanation: The power of a wave is given by P = 0.5 E^2/η, where E is the electric field intensity and η is the intrinsic impedance. On substituting for E = 12.8 and η = 377, we get P = 0.5 x 12.8^2/377 = 0.217 units.