# Classical Model Electrodynamics

• fred3142
In summary, the classical model of electrodynamics explains the behavior of plane waves hitting a conductor by using the concept of dipoles and electron movement. The wave reflects with a 180° phase shift because the electrons in the conductor re-arrange to cancel out the incident field, leading to an antiphase internal field that is re-radiated due to the conductor's inability to absorb energy. Math can be helpful in summarizing this behavior, but for a better understanding, one may need to consult sources that offer in-depth explanations without relying heavily on math.

#### fred3142

Hi,

I am trying to gain a better understanding of the classical model of electrodynamics, so what I mean by this is, using the idea of dipoles and electron movement to understand electrodynamics. More specifically, I'm studying plane waves, and I can't understand why when a plane wave hits a conductor, it reflects with a 180° phase shift. I 'get' why it reflects (electrons move in the conductor to oppose the incoming plane wave) but no idea why this would cause a phase shift. I thought only dipoles could cause phase shifts...

My books are filled with math and some offer limited explanations. Don't get my wrong, the maths is really helpful and certainly does neatly summarise what happens, it just doesn't offer much insight into why. I have other questions similar to the above one which I'm hoping I would be able to answer if I understood the model better. Could anyone point my to a source (book) that has actual explanations (I don't care much if it lacks maths, I have plenty of books with the maths...).

Thanks.

The simplest hand-waving explanation I know of is that a perfect conductor never has any field inside. Thus, when hit by an incident wave, its charges are re-arranged so that the incident field is exactly cancelled. That means the internal fields must by exactly in the antiphase. This field is then re-radiated (it has to be because a perfect conductor cannot absorb energy).

## 1. What is the Classical Model of Electrodynamics?

The Classical Model of Electrodynamics is a physical theory that describes the relationship between electric and magnetic fields and the motion of charged particles. It is based on the laws of electromagnetism developed by James Clerk Maxwell in the 19th century.

## 2. What are the main principles of the Classical Model of Electrodynamics?

The Classical Model of Electrodynamics is based on three main principles: Coulomb's law, which describes the force between two stationary charged particles; Gauss's law, which relates the electric field to the distribution of electric charges; and Faraday's law of induction, which states that a changing magnetic field will induce an electric field.

## 3. How does the Classical Model of Electrodynamics differ from Quantum Electrodynamics?

The Classical Model of Electrodynamics is a classical theory that describes electromagnetic phenomena on a macroscopic scale. It does not take into account the quantum nature of particles and their interactions. In contrast, Quantum Electrodynamics is a quantum field theory that describes the behavior of charged particles and their interactions with electromagnetic fields at the microscopic level.

## 4. What are some practical applications of the Classical Model of Electrodynamics?

The Classical Model of Electrodynamics has many practical applications in modern technology. It is used in the design of electric motors and generators, radio and television broadcasting, telecommunications, and many other electronic devices. It also underlies the principles of optics, which is the study of light and its interactions with matter.

## 5. What are some current research topics related to the Classical Model of Electrodynamics?

Some current research topics related to the Classical Model of Electrodynamics include the study of electromagnetic waves in complex media, the development of new materials with unique electromagnetic properties, and the use of electromagnetic fields for medical imaging and therapy. Additionally, scientists are also exploring the unification of classical and quantum theories of electromagnetism to better understand the fundamental nature of electromagnetic interactions.