When radiation of any kind- gamma rays, visible light, radio waves, etc. -impinges on a shell (as IT does on shell "A'' in the diagram), it stimulates the shell to absorb energy of that wavelength. This action reverses the function of the harmonic shell ("a"), causing it to become an emitter across the spectrum except for waves of the frequency mat triggered its partner (emission represented as -ir). Roughly half of this energy is absorbed by the inner side of the first shell, but where the harmonic shell lies outside the first, this broad-band radiation escapes into me second sphere (shells "B", "b ). Impinging on me ianer shell of the second sphere ("b"), the radiation stimulates that shell to absorb energy of the received wavelength (the whole spectrum except for IT). The outer shell then becomes the harmonic, and reverses its function to become an emitter across the spectrum except for waves of the frequency that triggered its partner. Since "b" is absorbing everything but 7t, "B" emits only tr, at the wavelength identical to the original stimulus.