Okay so if you put a florescent light bulb in front of a certain radio, the radio waves excite the mercury inside a causes them to emit UV light which makes the outer coating of the light bulb light up. But, how can this be if the radio waves are of a lower frequency and thus have less energy that the electrons in the mercury that emit a wave of UV light?


1 Answer 1


There are two separate processes going on. Radio waves provide a non-zero electric field throughout the gas. At any time in a gas, some small percentage of atoms are ionized due to thermal collisions. The resulting free electrons are accelerated by the electric field due to the radio waves. These accelerating electrons smash into other atoms, causing further ionization. This cascades, until the gas is largely ionized. This population of ionized electrons is constantly being recaptured by atoms, and then reionized. The capturing process releases UV rays.

So, you're right that the radio waves do not directly ionize the electrons - radio waves have too low a frequency to do so. The radio waves instead cause free electrons to accelerate until they collide with atoms, and that process ionizes more electrons. It is the ionized electrons that are randomly re-captured that produce the UV rays.

  • $\begingroup$ oh, so wait, then the radio waves would have to be of a high amplitude to accelerate the free electrons that much. I mean its teh law fo conservation of energy, what you put in is what you get out $\endgroup$
    – House
    Apr 7, 2015 at 1:49
  • $\begingroup$ Sure, the higher the amplitude, the more those charges are accelerated. $\endgroup$
    – Brionius
    Apr 7, 2015 at 9:13

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