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Electromagnetic Fields

Electromagnetic Fields

Electric fields generated by static charges, often referred to as electrostatic fields, are characteristically different from electric fields created by time-varying magnetic fields. While the former is a conservative field, implying that no net work is done on a test charge if it goes around in a complete loop in the field, the latter is, by definition, not a conservative field; net work is done, and it is proportional to the rate of change of magnetic flux.
However, the observation of Gauss's...

Dual Nature of Electromagnetic (EM) Radiation

Dual Nature of Electromagnetic (EM) Radiation

Electromagnetic (EM) radiation consists of electric and magnetic field components oscillating in planes perpendicular to each other and mutually perpendicular to radiation propagation through space. EM radiation can be classified as a wave, characterized by the properties of waves such as wavelength (denoted as λ) and frequency (represented by ν).
Wavelength is the distance between two consecutive peaks (the highest point) or troughs (the lowest point) in the wave. Frequency is the number of...

Intensity Of Electromagnetic Waves

Intensity Of Electromagnetic Waves

The energy transport per unit area per unit time, or the Poynting vector, gives the energy flux of an electromagnetic wave at any specific time. For a plane electromagnetic wave with E0 and B0 as the peak electric and magnetic fields and traveling along the x-axis, the time-varying energy flux can be given by the following equation:

Electromagnetic Waves in Matter

Electromagnetic Waves in Matter

Electromagnetic waves can travel in the vacuum as well as in matter. For example light, which is an electromagnetic wave, can travel through air, water, or glass.
Consider the electromagnetic wave passing through a dielectric medium. In such a case, Maxwell's equations get modified. In Ampere's law, ε0 , the dielectric permittivity of free space is replaced with ε, the permittivity of dielectric. Also, the vacuum permeability μ0 is replaced by the permeability of the medium, μ.
Furthermore, the...

Energy Carried By Electromagnetic Waves

Energy Carried By Electromagnetic Waves

Anyone who has used a microwave oven knows there is energy in electromagnetic waves. Sometimes, this energy is obvious, such as in the summer sun's warmth. At other times, it is subtle, such as the unfelt energy of gamma rays, which can destroy living cells. Electromagnetic waves bring energy into a system through their electric and magnetic fields. These fields can exert forces and move charges in the system and, thus, do work on them. However, there is energy in an electromagnetic wave,...

Electromagnetic Waves

Electromagnetic Waves

James Clerk Maxwell formulated a single theory combining all the electric and magnetic effects scientists knew during that time, calling the phenomena his theory predicted “Electromagnetic waves”. He brought together all the work that had been done by brilliant physicists such as Oersted, Coulomb, Gauss, and Faraday and added his own insights to develop the overarching theory of electromagnetism. Maxwell’s equations, combined with the Lorentz force law, encompass all the laws of electricity and...

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Related Experiment Video

Updated: Jun 22, 2026

New Framework for Understanding Cross-Brain Coherence in Functional Near-Infrared Spectroscopy (fNIRS) Hyperscanning Studies

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Degree of coherence for electromagnetic fields.

Jani Tervo, Tero Setala, Ari Friberg

|May 26, 2009

Summary

The study reveals flaws in the standard definition of electromagnetic field coherence. A new, more accurate measure is introduced, offering unique insights into electromagnetic fields and their interference patterns.

Area of Science:

Optics and Photonics
Quantum Optics
Electromagnetism

Background:

Spatial coherence is crucial for understanding interference phenomena.
Existing definitions of coherence may not fully capture the complexities of electromagnetic fields.
Two-pinhole interference experiments are fundamental for probing wave properties.

Purpose of the Study:

To assess the relationship between fringe visibility and spatial coherence in electromagnetic two-pinhole interference.
To identify and rectify limitations in the customary definition of the degree of coherence for electromagnetic fields.
To introduce a novel, formally robust definition of electromagnetic field coherence.

Main Methods:

Analysis of fringe visibility in two-pinhole interference patterns.

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Last Updated: Jun 22, 2026

New Framework for Understanding Cross-Brain Coherence in Functional Near-Infrared Spectroscopy (fNIRS) Hyperscanning Studies

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Theoretical derivation and validation of a new coherence metric.

Comparison of the new definition with established results for Gaussian statistics.

Main Results:

The customary definition of the degree of coherence for electromagnetic fields is demonstrated to be flawed.
A new quantity for the degree of coherence is introduced, overcoming formal drawbacks.
The new definition exhibits unique properties specific to electromagnetic fields, distinct from scalar fields.

Conclusions:

The proposed new definition of electromagnetic coherence is experimentally measurable through interference experiments.
This work provides a more accurate framework for understanding spatial coherence in electromagnetic wave phenomena.
The findings have implications for advanced optical systems and quantum information processing involving electromagnetic fields.