The amplitude of the electric field component of an electromagnetic wave is increased from E to 3E. What is the corresponding change in the intensity of the wave?
A)The intensity is unchanged by the increase in E.
B)The intensity increases by a factor of nine.
C)The intensity increases by a factor of three.
D)The intensity decreases by a factor of three.
E)The intensity decreases by a factor of nine.

Question

Quizplus · Accepted Answer

The intensity of an electromagnetic wave is proportional to the square of the electric field amplitude. Therefore, if the electric field amplitude is increased by a factor of 3, the intensity will increase by a factor of (3)^2, or 9. Thus, the correct answer is B, the intensity increases by a factor of nine.

The Amplitude of the Electric Field Component of an Electromagnetic