Electromagnetic Waves: A Confusing Abstraction

[darkchild]

I am having some trouble understanding the concept of electromagnetic waves, I suppose because I expect them to be analogous to physical waves you can see or touch (such as on a string). Yes, I know one can actually see them at visible wavelengths, but that doesn't help because I don't experience light as a wave.

First of all, there's wavelength. This should be a physical distance, according to the units, but the question is: the distance from where in space to where?

Someone tried explaining to me something to the effect that, if one of the fields is at its maximum strength at some point in space, the distance between that point and the next point in space at which that same maximum occurs (along the direction of propagation) determines the wavelength. Well, that raises the question of what exactly is "propagating." I'm sure my old professor would say that the fields are propagating, but that tells me nothing about the real world because the fields are just abstractions, not actual objects that can move. So, what precisely is moving along?

Also, please help me out with the electric field of a moving charge. If we have a single charged particle just sitting somewhere, the electric field can be represented by field lines pointing outward radially. If the particle starts moving, I'm picturing those field lines picking up stakes and moving right along with it, so that, at any instant in time, the electric field is exactly the same as in the case of electrostatics. I'm guessing that's totally wrong, though.

I think my biggest problem is my inability to tell the difference between what physics explanations are just part of an abstract model and what is actually, physically going on, or what could be detected. Of course, in a sense physics is all abstract models, but hopefully people understand what I mean when I assert that some of it is more "real" (things we can touch and see, like force or friction) than other parts of it (things that are totally made up, like fields).

Thanks.

 

[valleyman]

good question, I'm waiting for some answer too

 

[astrokreng]

I completely understand your confusion and frustration with the concept of electromagnetic waves. It is true that these waves cannot be seen or touched like physical waves on a string, and this can make it difficult to grasp the concept. However, I assure you that electromagnetic waves are very real and have a significant impact on our daily lives.

To address your questions, let's start with the concept of wavelength. You are correct in thinking that it is a physical distance, but the distance is not from one point in space to another. Instead, it is the distance between two consecutive peaks or troughs of the wave. In the case of electromagnetic waves, these peaks and troughs represent the maximum and minimum values of the electric and magnetic fields.

Now, to your question about what is "propagating" in electromagnetic waves. It is the disturbance in the electric and magnetic fields that is propagating through space. Think of it like a ripple on the surface of a pond - the water itself is not moving, but the disturbance is propagating through the water. Similarly, in electromagnetic waves, the fields themselves are not moving, but the disturbance is propagating through the fields.

As for the electric field of a moving charge, your understanding is partially correct. The electric field of a stationary charge can be represented by field lines pointing radially outward, but when the charge is in motion, these field lines will also change and move along with the charge. This is because the motion of the charge creates a changing electric field around it, which in turn creates a changing magnetic field, and the two together form an electromagnetic wave.

Finally, I understand your struggle with distinguishing between abstract models and physical reality. While fields may seem like abstract concepts, they are actually very real and can be measured and detected. For example, we use electromagnetic fields every day in radios, cell phones, and Wi-Fi signals. These fields may not be tangible, but they have a very tangible impact on our lives.

I hope this explanation has helped to clarify some of your confusion about electromagnetic waves. It is a complex and abstract concept, but it is a fundamental part of our understanding of the physical world. Keep asking questions and seeking understanding, and I am confident that you will continue to deepen your understanding of this fascinating topic.