Help Layman Understand EM Wave Propagation

In summary, the conversation discusses the propagation of electromagnetic waves and how it differs from sound waves. It is explained that light can be thought of as a transverse wave in the electromagnetic field, and that photons are the quanta of this wave. The concept of waves and particles in quantum mechanics is also mentioned, and it is stated that light is not a complete mystery but rather well-understood through QED. The limitations of using analogies to understand light are also emphasized.
  • #1
Theheretic
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0
Hello everyone. I have tried to do as much research as my layman mind will allow on how an electromagnetic wave propagates in relation to how a sound wave for example does.

I understand that an acoustic wave is longitudinal and works on compression and that a light wave is a transverse wave that propagates perpendicular to the direction.

But I just don't understand how exactly it is propagating. I mean I know that science probably doesn't 100% understand it either but can someone clear up any of it at all? Or is it a complete 100% mystery?

For example let's say light is a packet of photons and they are traveling in a straight line, what is it exactly that is acting as a wave? If it is the photons that are transversely waving from side to side, what is it that's making them go from one side then come back to the other instead of flitting away in random directions? Is it the 'magnetic field' property? Is there basically a magnetic field around each photon that is making it swing like a pendulum in frequencies?

How does it work...?

Thank you.
 
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  • #2
From a classical electromagnetic theory, light can be thought of as a transverse wave in the electromagnetic field of a charged particle. So if I have a charged sphere and wiggle it, it will give off an electromagnetic wave that travels through the EM field of the sphere. Some phenomena can only be understood using this wave idea. Similarly, some phenomena can only be understood by thinking of light as a discrete particle like entity. The view of quantum mechanics is that the phenomena are real, but the wave/particle pictures are just stories we tell ourselves about what is happening. When you picture a photon as a little ball or point traveling in a straight line from point A to point B, that isn't a good way to think about it. Picturing it as a ball may sometimes help to explain what happens at B when its detected, but we'd be in error if we assumed it was a ball that traveled in straight lines all the time. The main thing is that if we accept both pictures, we can describe all the phenomena...they are opposite and contradictory, but they compliment each other. As Bohr would say, opposites are compliments.
 
  • #3
Photons are themselves quanta of an EM wave, they are not the medium in which the "vibration" is occurring.

Additionally, EM waves do not represent oscillations in displacement (like water waves, or sound waves do), but oscillations in the amplitude of an electromagnetic field.

Claude.
 
  • #4
EDIT: Claude Bile beat me to it. I didn't see his post, sorry.

Our normal intuition, built up from everyday life, leads us to believe that all waves must propagate in some medium. This idea is false for light, as I'm sure you probably know.

An example of transverse waves would be ripples in a pond. However, you should not take this analogy too far as water waves occur on a 2-dimensional boundary while light waves occur in 3-d space. Also, water waves have only one component (height) while EM waves have electric and magnetic components. Ultimately, we are incapable of visualizing EM waves directly. The best you can do is mathematical manipulation.

But I just don't understand how exactly it is propagating. I mean I know that science probably doesn't 100% understand it either but can someone clear up any of it at all? Or is it a complete 100% mystery?

Light is not a complete mystery. In fact it is quite the opposite; QED explains light so perfectly that you could say light is probably one of the best-understood phenomena in the Universe. Now gravity, that is what I would call tricky.

For example let's say light is a packet of photons and they are traveling in a straight line, what is it exactly that is acting as a wave? If it is the photons that are transversely waving from side to side, what is it that's making them go from one side then come back to the other instead of flitting away in random directions? Is it the 'magnetic field' property? Is there basically a magnetic field around each photon that is making it swing like a pendulum in frequencies?

Photons do not wave around, at least not in the classical sense of waving around. The DeBroglie picture is not wrong though, just incomplete.
In a sense, the photons are the waves.
Again, both the wave picture and the particle picture of light are both analogies and abstractions of a deeper physical truth, part of which has been captured in QED. You should not take these analogies too far as they will lead you into trouble. You should also know that these problems are resolved with the mathematics of QED.
 
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1. What is an electromagnetic wave?

An electromagnetic wave is a type of energy that is made up of electric and magnetic fields that are oscillating and perpendicular to each other. These waves are created when electrically charged particles, such as electrons, accelerate. They do not require a medium to travel through, meaning they can travel through empty space.

2. How do electromagnetic waves propagate?

Electromagnetic waves propagate through the process of oscillation. This means that the electric and magnetic fields are constantly changing, creating a wave-like pattern. These waves travel at the speed of light in a vacuum and can travel through different materials at different speeds.

3. What are the different types of electromagnetic waves?

There are several types of electromagnetic waves, which are classified based on their frequency and wavelength. These include radio waves, microwaves, infrared waves, visible light, ultraviolet waves, X-rays, and gamma rays. Each type has a different frequency and wavelength, which determines its properties and uses.

4. How are electromagnetic waves used in everyday life?

Electromagnetic waves have a wide range of uses in our daily lives. Radio waves, for example, are used for communication, while microwaves are used for cooking. Infrared waves are used for remote controls and thermal imaging, and visible light is essential for vision. Ultraviolet waves have uses in medicine and sterilization, while X-rays are used in medical imaging. Finally, gamma rays are used in cancer treatment and sterilization.

5. What factors affect the propagation of electromagnetic waves?

The propagation of electromagnetic waves can be affected by various factors, including the frequency and wavelength of the wave, the medium it is traveling through, and any obstacles or interference it may encounter. The properties of the medium, such as its density and composition, can also affect how the wave propagates. Additionally, the strength and direction of the electric and magnetic fields can impact the propagation of the wave.

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