It is the interaction of light with electrons that is responsible for its creation and destruction. Electrons in matter can be described as occupying energy levels. Figure 1 . In Fig 1c, an electron in the upper level moves to the lower level by giving up an energy of 2 eV and emitting orange light.
Energy is conserved.
From the quantum theory, we know that the electrons are bound to the atom with fixed energies, the binding energies. This means that an energy of at least 1.839 keV must be given to an innermost electron to remove it from the silicon atom. These 1 keV energies lie in the x-ray portion of the spectrum. The outermost electrons in silicon have a binding energy of 3 electron volts. This is at the upper end of the visible light energy spectrum.