Question about electromagnetics (waves and particles)

[samy4408]

I saw that we can talk about the light as particles (photons ) or as an electromagnetic wave , the question is that do we represent other electromagnetic waves (like microwaves or radio waves ) as particles (like we do with light ) ?

 

[PeroK]

I saw that we can talk about the light as particles (photons ) or as an electromagnetic wave , the question is that do we represent other electromagnetic waves (like microwaves or radio waves ) as particles (like we do with light ) ?

Yes. Quantum Electrodynamics (the quantum mechanical theory of light) applies to the entire electromagnetic spectrum.

In general there is no physical distinction between visible light and light that our eyes do not detect, such as radio waves, microwaves, x-rays, infrared and ultraviolet radiation.

 

[Baluncore]

I saw that we can talk about the light as particles (photons ) or as an electromagnetic wave , the question is that do we represent other electromagnetic waves (like microwaves or radio waves ) as particles (like we do with light ) ?

We use the model that works best for us at the time.
"(like microwaves or radio waves )". The fact that we call them waves is a clue that the photon model is not as useful as the wave model.

Consider a 100 MHz 1 watt transmitter.
Photon energy; E = h⋅freq; where Planck constant, h = 6.62607015×10^-34 J / Hz.
E = 6.626e-34 * 1e8 = 6.626e-26 joule per photon.
1 watt is 1 joule per second. That is 15.1×10²⁴ photons per second.
Counting photons at radio frequencies is going to be quite difficult.

 

[sophiecentaur]

Counting photons at radio frequencies is going to be quite difficult.

Once you get to visible light, individual photons can be fairly easily measured with photo sensors and people claim that individual photons can be seen by a fully dark adapted human eye as tiny flashes of light 'in the pitch dark'. (Never saw it myself and I wonder whether it's just random noise on the retina.)
Go up a bit higher in frequency and individual γ photons are easily heard with the clicks and crackles of a Geiger counter from a very low intensity Gamma Ray source.

 

[Albrecht]

We use the model that works best for us at the time.
"(like microwaves or radio waves )". The fact that we call them waves is a clue that the photon model is not as useful as the wave model.

Consider a 100 MHz 1 watt transmitter.
Photon energy; E = h⋅freq; where Planck constant, h = 6.62607015×10^-34 J / Hz.
E = 6.626e-34 * 1e8 = 6.626e-26 joule per photon.
1 watt is 1 joule per second. That is 15.1×10²⁴ photons per second.
Counting photons at radio frequencies is going to be quite difficult.

That is a great response. When I asked for a specific property of photons as particles some time ago, I got the response that photons are clearly waves and not particles and that I am stating nonsense by asking for particles; and my access to the forum was blocked. What has changed?

 

[Baluncore]

What has changed?

You asked the right question. It was answered by a pragmatic engineer. I half expected to be punished for having strayed from the Engineering into the Physics part of the forums.

It is important that while exploring Physics for the first time, you have faith, and avoid questioning the fundamental paradigms.

The application of the particle tools and the wave tools overlap. Use what works best in your application. If you insist on defining a hard boundary, you must be wrong in some way.

 

[Mister T]

For the wave properties to appear you need large numbers of photons.

 

[Mister T]

I got the response that photons are clearly waves and not particles

You must have misunderstood what you saw or you remember it incorrectly. Photons are particles. If you have a large collection of photons then the wave properties can appear.

 

[sophiecentaur]

Photons are particles.

There's a lot more to that statement than you are implying. Just what do you mean when you use the word 'particle'? First thing is that you cannot treat a photon as a little bullet; its position and 'extent' have no meaning so a flash of light is not a shower of photons (in the way people understand what a shower is).

It's a lot easier if we limit our mental picture of a photon as a packet of energy. That's all we can be really sure of from experiment.

Using the word Photon in an argument or description (at least at this level of things) will, in no way, make the argument any more substantial or demonstrate better understanding. Second order partial differential equations are hard so it's forgivable to try to avoid the (wave) description of many optical phenomena but you cannot get away from them by trying for the photon approach. PDE's also sneak into describing what a photon will do.

 

[Maarten Havinga]

I would say photons are better described by their wavefunction (complex and real part of it) and are therefore wave packets. Only on measurement they become pointlike particles, by some unknown process observed as wavefunction collapse.

 

[Klystron]

As stated, use the tool appropriate to the task at hand. To list some items

• The electromagnetic (EM) radiation spectrum is continuous from large to tiny wavelengths or small to large frequencies as you prefer. Wavelength and frequency are reciprocal measurements.
• Engineers often prefer the term wavelength while others use frequency, as for radio stations.
• 
  
• Wave terminology for EM is ubiquitous and useful but EM fields mathematically describe EM radiation. Radio transmissions, microwaves, light waves, X-rays are the same thing measured at different frequencies for different applications.
• 
  
• Photons (bosons) are the quanta of EM energy useful for describing EM at the smallest discrete level.
• Electrons (leptons) appear to be the elementary particle at the root of EM phenomena.
• Terminology and theories progress over time as new technology improves measurement.

To paraphrase previous comments, we mostly measure and manipulate EM radiation as fields and herd electrons as aggregate charge carriers. Articles and textbooks describe physics experiments using the equipment, theories and mathematics available in their time. Try to learn as much mathematics as you are able in order to really understand science and engineering.