Electromagnetic wave emission after source vanishes

AI Thread Summary
Electromagnetic waves can continue to propagate even after the source has stopped emitting them. When a charge accelerates, it creates a disturbance in the electric field, which in turn generates a magnetic field, allowing them to sustain each other. If the source charge vanishes, the existing changing electric and magnetic fields will still propagate outward. This phenomenon is similar to ripples in a pond that continue to spread after a pebble is thrown in, despite no new waves being generated. The discussion clarifies that the waves do not cease immediately upon the source's disappearance.
PeteyCoco
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I'm reading about electromagnetic waves and I can't make sense of their self-sustaining nature. If a charge accelerates for a moment and then stops a disturbance in the electric field is sent out. This changing electric field creates a changing magnetic field and they continue to sustain each other, propagating infinitely outward. Now, if the source charge were to vanish there would still be a changing E/B field in its immediate vicinity which will continue to exist. Wouldn't this mean that the waves are emitted forever?
 
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Nevermind. Stupid question.
 
no, not a stupid question

Yes the EM wave continues to propagate outwards after the source stops emitting

not really too different than if you throw a pebble into a pond, the initially generated waves will still radiate outwards, even tho new waves are not being created at the source

Dave
 
I was using the Smith chart to determine the input impedance of a transmission line that has a reflection from the load. One can do this if one knows the characteristic impedance Zo, the degree of mismatch of the load ZL and the length of the transmission line in wavelengths. However, my question is: Consider the input impedance of a wave which appears back at the source after reflection from the load and has traveled for some fraction of a wavelength. The impedance of this wave as it...
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