I know that there is a particle model that describes the absorption of electromagnetic radiation in matter - A photon with energy E can excite ("absorbed") an atom if it has energy gap of the same size E.
What about a wave model for absorption, or is it only a particle phenomena ?
In the particle model, as you rightly pointed out, absorption is described in terms of photons — quantized packets of electromagnetic energy. When a photon with energy E encounters an atom, it can be absorbed if the atom has an energy gap of the same size E. This process is quantitatively described by Einstein's theory of the photoelectric effect and is a cornerstone of quantum mechanics.
Now, let's turn to the wave model. In classical electromagnetism, light is treated as a wave, characterized by its electric and magnetic fields. When an electromagnetic wave encounters a material, its oscillating electric field can interact with the charged particles (such as electrons) within the material. This interaction depends on the frequency of the electromagnetic wave and the natural frequencies of the electrons in the material.
If the frequency of the incoming electromagnetic wave matches a natural frequency of oscillation of electrons in the material, resonance occurs. At resonance, electrons absorb energy from the wave efficiently. This absorption leads to a transfer of energy from the electromagnetic wave to the material, resulting in the wave's amplitude decreasing as it passes through the material — a phenomenon we interpret as absorption.
So, in the wave model, absorption is not about discrete energy packets being transferred, but rather about the resonant transfer of energy from the wave to the material at specific frequencies. This model is particularly useful for explaining phenomena like why certain materials are transparent at some wavelengths but opaque at others.
In conclusion, the absorption of electromagnetic radiation in matter can indeed be described using both the particle and wave models. While the particle model (photon absorption) provides a more intuitive explanation for discrete energy exchanges, the wave model (resonant energy transfer) offers insight into the frequency-dependent nature of absorption. Both perspectives are complementary, reflecting the dual nature of light as both a wave and a particle, a fundamental concept in modern physics.
Arham Zahid has already described what happens when EM radiation hits the atomic level "by Einstein's theory of the photoelectric effect".
However, if one attempts to measure the wave character of visible light using a receiving antenna, this attempt fails. And this is not only due to the frequency of the light, but also to the properties of the light source. With a thermal source, the photons are emitted chaotically and are also not polarised. The electrons that are hit by such photons scatter the incoming energy and ultimately the temperature of the receiving body increases.
What about a wave model for absorption, or is it only a particle phenomena?
If the electrons in an antenna rod are accelerated synchronously forwards and backwards, polarised photons are emitted. With varying intensity. All photons together generate an EM wave, with their electric and magnetic field components, both perpendicular to each other and perpendicular to the direction of propagation and travelling forwards at c. A tiny fragment of this wave now hits the receiver and synchronously moves electrons up and down in a conductor. The tuned electronics can now filter out the sinusoidal wave from the rest of the EM radiation.
Yes, there are several wave models of EM absorption and emisslon. The most elaborate of these is John Cramer's Transactional Interpretation of Quantum Mechanics TIQM. Cramer's model is essentially modified from the older Wheeler-Fymann absorber theory by eliminating the fantasy and magic of the W-F model. Information about Cramer's model can be found in Wiki and the entire TIQM can be found online.
A good readable account of how energy is exchanged among particles consistent with Cramer's model can be found in the book Collective Electrodynamics chapter 5 by Carved A. Mead. In his book, Mead explains how energy is never found separate from matter and how energy is transferred from directly from one particle to another by means of a wave-like resonance rather than by a space traveling particle called a photon.
Another wave model much like the above is the Pope-Osborne Angular Momentum Synthesis POAMS by N.Viv Pope and Anthony Osborne. POAMS makes it emphatic that the constant c is not the speed of light but instead a dimensional constant in which distances separated by space are simultaneously separated by time at the ratio of one second for every 300,000 km. This makes c a ratio rather than a speed. The delay we see in an EM energy exchange is due to the amount of distance AND time (spacetime) we see between events at the ratio of c and not the due to the speed of light which is remote from our concept of time.
In both of the above models, EM energy exchanges among particles are direct particle to particle exchanges without the intuitive necessity of having energy pass through the space between either by itself or carried by a particle.
