Savchenko Problem 12.1.22
Physics · mechanics · fluid-mechanics
Problem
The amplitude of the electric field strength of a plane sinusoidal wave is equal to E₀. What is the average pressure exerted by this wave on a flat metal wall when it is normally incident on it?Intuitive explanation
When electromagnetic waves hit a conductor, they transfer momentum—and that momentum transfer creates pressure. The key insight is that the electric field oscillates sinusoidally, so you need to find the average energy density (which depends on ), then use the relationship between radiation pressure and intensity. For a perfectly reflecting metal wall with normal incidence, the pressure depends on how much momentum the wave carries per unit time per unit area.
Intuitive explanation
When electromagnetic waves hit a conductor, they transfer momentum—and that momentum transfer creates pressure. The key insight is that the electric field oscillates sinusoidally, so you need to find the average energy density (which depends on ), then use the relationship between radiation pressure and intensity. For a perfectly reflecting metal wall with normal incidence, the pressure depends on how much momentum the wave carries per unit time per unit area.