Radio wave photons and light photons have a different wavelength. But they also appear to have a much different "thickness" in that light photons "fit" cleanly through small pigeonholes, where the corresponding radio wave would interact with its border.

So the two kinds of radiation don't seem to only differ in wavelength as such - a property that is much more subtle - but also in it's "diameter" (the extent of possible interaction orthogonal to their travelling direction).

If that is correct so far, I wonder why that isn't spelled out in introductory textbooks more often - it seems to be the much more intuitively understandable concept than the wavelength.

If that is true, my next question would be if that extent is the same, or roughly the same, as the quantum-mechanical wave-function: I.e, does the space with a reasonable probability to "find the particle" in (not that I have yet fully understood what that means) spread around the line of traveling more for lower-frequency particles?

If that is also true, does that not mean that the general idea of elementary particles as sub-microscopical is flawed in that particles are really entities of any size - in particular including macroscopic sizes?

  • $\begingroup$ You are suffering from a misconception. A classical electromagnetic wave of a given wavelength can exist on any length scale, including ones that are much smaller than the wavelength. Classical theory predicts that if the length scale is smaller than the wavelength the interaction with matter will be very weak. Observations shows this not to be true in general (atomic absorption/emission lines) and quantum mechanics explains why classical theory fails in making the correct predictions. $\endgroup$ – CuriousOne Jan 1 '15 at 18:55
  • $\begingroup$ I would also suggest that you read some of the wave-particle duality questions on this site to get an idea for why particles don't exist in the quantum world. What exists are quanta, but thats a completely independent concept. $\endgroup$ – CuriousOne Jan 1 '15 at 19:11
  • $\begingroup$ @CuriousOne Both those objections don't seem to address the question: Why does a wave with a smaller wavelength fit through smaller holes? The answer to that won't care about whether EM waves are particles or not, right? The answer will also not care about the length scale (in traveling direction) of the wave, right? $\endgroup$ – John Jan 2 '15 at 11:05
  • $\begingroup$ The wavelength of an electromagnetic wave is not the same as its size. There is no such thing as a size for an electromagnetic wave and bringing particles into the picture only confuses the problem (there are no such things as particles to begin with). The only question one can ask is what happens if we try to excite an electromagnetic wave of a certain frequency in a certain geometry. As it turns out, one can excite these just fine, they will simply not travel very far if the volume is smaller than the wavelength, and this is true for any direction. $\endgroup$ – CuriousOne Jan 2 '15 at 11:16

Electromagnetic waves travel in the form of time varying electric and magnetic feilds and the are produced by accelerated electric charges or it can be produced in a nuclear transition or in the annihilation of an eletron or positron they travel with the speed of light and their velocity is 3x10 raise to 8 m/s


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