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justwild
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In wikipedia's description of transmitter, if an alternating current is given to an antenna, then the antenna radiates off em wave.
But why this happens so?
But why this happens so?
The simplistic description is this:
1. An electric current produces a magnetic field.
2. An oscillating (alternating) electric current produces an oscillating magnetic field.
3. An oscillating magnetic field "produces" an oscillating electric field, which in turn "produces" more oscillating magnetic fields, which in turn "produce" more oscillating electric fields, etc. via the time-derivative terms in Maxwell's equations. These oscillations propagate at speed c.
A more accurate version of step 3 is that oscillating magnetic fields are inevitably associated with oscillating electric fields, both propagating at speed c, again via the time-derivative terms in Maxwell's equations. This avoids the implication of a circular cause and effect chain.
Ok, oscillating electric current can produce electromagnetic waves from an antenna. Frequency of generated electromagnetic wave is the same as frequency of oscillations of current in the antenna. I think I'm correct on my last sentence.
Then I think it is also possible to observe visible light from an antenna by controlling frequency of oscillations of its current.
Just a thought.