Answer
The energy of the radio waves excited electrons in some neon atoms. When the free electrons return back to their original states, they release the excess energy as photons.
Work Step by Step
Neon signs are glass tubes filled with neon gas. When the sign is turned on, an electric current begins to flow through the tube. This current causes some of the valence electrons of some neon atoms to break free from their orbits. As these free electrons move from one electrode to the other, they collide with neon atoms and cause other electrons to break free. Eventually, the excited electron falls back into their normal energy level in one of the positively charged ions and releases their excess energy as photons.
The radio station emits radio electromagnetic waves. The energy carries by these waves causes the electrons in some neon atoms in the tube to break free. When they fall back into their normal energy level, they emit photons. Because there is not a significant amount of energy being transmitted, a smaller percentage of electrons get excited, causing the glow to be fainter.
