EM Field vs EM Wave: Understanding Distance & Strength Differences

[spacebear2000]

Why does the strength of an electrical field diminish with distance from its source whereas the amplitude and frequency of a beam of light do not vary, regardless of distance?

 

[kote]

Why does the strength of an electrical field diminish with distance from its source whereas the amplitude and frequency of a beam of light do not vary, regardless of distance?

Spacebear, one way to think of it is that even though the individual photons may not lose energy, they are more spread out as you move farther from a source - you have fewer and fewer photons interacting with whatever it is you are using to measure the strength.

The flux or intensity can tell you how much spreading out has occurred and how much relative "strength" you have left at any region.

 

[astrokreng]

The difference between an electromagnetic (EM) field and an EM wave lies in their fundamental properties and behavior. An EM field is a region of space where electric and magnetic forces are present, while an EM wave is a disturbance that propagates through space, carrying energy and information. The strength of an EM field is determined by the magnitude of the electric and magnetic fields present in the space, while the amplitude and frequency of an EM wave are determined by the strength and frequency of the oscillating electric and magnetic fields.

The strength of an electrical field diminishes with distance from its source due to the inverse square law. This law states that the strength of an electric field is inversely proportional to the square of the distance from its source. This means that as the distance from the source increases, the strength of the electric field decreases rapidly. This is because the energy of the electric field is spread out over a larger area, resulting in a decrease in its strength.

On the other hand, the amplitude and frequency of an EM wave do not vary with distance because EM waves are self-propagating. This means that as the wave travels through space, it maintains its amplitude and frequency without any loss of energy. This is due to the fact that EM waves do not rely on a medium to propagate, unlike sound waves which require a medium such as air to travel. As a result, the amplitude and frequency of an EM wave remain constant regardless of the distance traveled.

In summary, the strength of an electrical field diminishes with distance from its source due to the inverse square law, while the amplitude and frequency of an EM wave remain constant due to their self-propagating nature. Understanding these differences is crucial in various fields of science and technology, such as telecommunications, where the properties of EM fields and waves play a significant role in signal transmission and reception.