Below is a paragraph taken from the web site, physicsclassroom.com:
It is often useful to think of these electrons as being attached to the atoms by springs. The electrons and their attached springs have a tendency to vibrate at specific frequencies. Similar to a tuning fork or even a musical instrument, the electrons of atoms have a natural frequency at which they tend to vibrate. When a light wave with that same natural frequency impinges upon an atom, then the electrons of that atom will be set into vibrational motion. (This is merely another example of the resonance principle introduced in Unit 11 of The Physics Classroom Tutorial.) If a light wave of a given frequency strikes a material with electrons having the same vibrational frequencies, then those electrons will absorb the energy of the light wave and transform it into vibrational motion.
Can the above be right? Wouldn't the vibrational frequencies of the electrons in atoms be just non classical? How could there be a natural frequency of the electrons that matches a light wave with the same natural frequency if one is non classical (the electron) and the other is classical (the light wave)?
Perhaps they have this all wrong and resonance just refers to vibrational frequencies of molecules matching specific light wave frequencies. But that idea seems unlikely since molecules just vibrate within the infra-red range. For example, I've heard that the human body has a resonant frequency around 68 Hz. I've heard all objects have a resonant frequency.
What is meant by the resonant frequency of an object?