EM Wave creation in different frames of reference

In summary, there are two observers, one stationary (S) and one moving back and forth (A) in front of a charged particle. S sees no magnetic field from the particle, while A sees the particle as accelerating and decelerating, creating an electromagnetic wave. However, from S's perspective, there is no EM wave. The difference between the two perspectives is due to the fact that A is accelerating while S is not, making them non-equivalent observers. This highlights the need for special relativity when calculating the exact speed of electromagnetic radiation.
  • #1
ealbers
34
0
OK, I'm sure I'm just not thinking about this the right way, so please point out my simple mistake.

Imagine a charged particle and 2 observers.

Observer S is stationary relative to the charged particle, so sees no magnetic field from it.

Observer A moves back and forth in front of the particle, accelerating, then decelerating over and over, back and forth.

Would not Observer A see the charged particle as accelerating and decelerating, from their point of view/frame of reference?
Would not the acceleration of a charged particle from Observers A perspective create a EM wave which would propagate outwards?

Now from Observer S's perspective, there is just a charged particle and the other Observer moving around, no EM wave is created.

What am I missing??
Thanks for your time!
E
 
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  • #2
Because S and the particle are moving back and forth (as opposed to inertially, in a straight line with constant speed) they know that they are being accelerated at each turnaround. S and A are not equivalent observers; if they're both holding a mass on a spring, S's spring is alternately tensing and relaxing while A's is not. Thus, they both know to do the calculations for an accelerated charge I stead of one at rest.

(Be aware, however, that you still will find a problem if you try calculating the exact speed of the electromagnetic radiation relative to the two observers using classical physics. That's why we need special relativity)
 

Related to EM Wave creation in different frames of reference

1. What is an EM wave?

An electromagnetic (EM) wave is a type of wave that is created by the oscillation of electric and magnetic fields, and carries energy through space. It is composed of perpendicular electric and magnetic fields that are in phase with each other and travel at the speed of light.

2. How is an EM wave created in different frames of reference?

In different frames of reference, an EM wave is created when an electric charge accelerates or decelerates. This acceleration causes a disturbance in the surrounding electric and magnetic fields, resulting in the creation of an EM wave that travels outward from the source.

3. Can the creation of an EM wave be observed in all frames of reference?

Yes, the creation of an EM wave can be observed in all frames of reference. However, the observed properties of the wave, such as its frequency and wavelength, may vary depending on the observer's frame of reference due to the effects of relativity.

4. How does the creation of an EM wave in different frames of reference affect its speed?

The creation of an EM wave in different frames of reference does not affect its speed, as the speed of light is constant and independent of the observer's frame of reference. However, the observed frequency and wavelength of the wave may change, resulting in a perceived change in its speed.

5. What is the significance of understanding EM wave creation in different frames of reference?

Understanding EM wave creation in different frames of reference is crucial in modern physics, as it helps us to better understand the fundamental principles of relativity and how the laws of physics apply in different reference frames. This knowledge also has practical applications in technologies such as GPS and satellite communication.

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