What is the amplitude of an EM wave?

Click For Summary
SUMMARY

The amplitude of an electromagnetic (EM) wave is a crucial parameter that relates to its intensity, which is defined as the power per area. The relationship between the electric field amplitude (E_0) and intensity (I) is given by the formula I = E_0² / (2cμ₀), where c is the speed of light and μ₀ is the permeability of free space. To derive the amplitude, one must consider the energy density of the electric (E) and magnetic (B) fields, as outlined in standard electromagnetic textbooks. Understanding this relationship is essential for grasping the fundamental properties of EM waves.

PREREQUISITES
  • Basic understanding of electromagnetic wave theory
  • Familiarity with the concepts of electric field (E) and magnetic field (B)
  • Knowledge of the speed of light (c) and permeability of free space (μ₀)
  • Ability to interpret mathematical formulas related to physics
NEXT STEPS
  • Study the derivation of energy density in electromagnetic fields
  • Learn about the relationship between intensity and amplitude in EM waves
  • Explore the role of the speed of light and permeability in wave equations
  • Review relevant sections in standard electromagnetic textbooks for deeper insights
USEFUL FOR

Students and professionals in physics, electrical engineering, and anyone interested in the properties of electromagnetic waves and their applications.

iScience
Messages
466
Reaction score
5
i always hear about the frequency/wavelength, and the speed of the wave, but i never heard about the actual amplitude of the wave itself? how would one derive this? I'm not referring to intensity... intensity deals with the number of photons being captured by a detector... I'm referring to the actual amplitude of the EM wave itself. if it truly is a wave, it MUST have an amplitude right? what is it? how do i derive it?
 
Physics news on Phys.org
Page 11 of this link gives the relation between E-field amplitude E_0 and intensity (power per area) I as

I = \frac{E_0^2}{2 \ c \ \mu_0}

Edit added:
The derivation comes from writing the energy density in terms of E and B (as given in any decent E-M textbook), and then using

\text{Intensity} = \text{Energy density} \cdot c
 
Last edited:

Similar threads

Undergrad Mechanism of Energy Conservation in Zero-Amplitude Sum of EM Waveforms
  • · Replies 21 ·
Replies
21
Views
3K
Undergrad Energy emitted by EM sources under constructive interference
  • · Replies 7 ·
Replies
7
Views
2K
Graduate EM waves, longitudinal EM propagation?
  • · Replies 15 ·
Replies
15
Views
3K
Undergrad What determines if wave components are independent vs coherent?
  • · Replies 3 ·
Replies
3
Views
816
Graduate Frequency of EM waves produced by linearly accelerating charges
  • · Replies 20 ·
Replies
20
Views
2K
Graduate Want accurate cartoons of EM Waves
  • · Replies 5 ·
Replies
5
Views
4K
Undergrad EM Power transmitted from one region to another (normal incidence)
  • · Replies 6 ·
Replies
6
Views
1K
Graduate Splitting and combining EM waves & amplitude/intensity
  • · Replies 11 ·
Replies
11
Views
3K
Undergrad Photon Displacement in EM Waves (Amplitude)
  • · Replies 8 ·
Replies
8
Views
3K
Undergrad EM wave propagation: respective phase of E and M field
  • · Replies 6 ·
Replies
6
Views
2K