system
Given the following post, respond as if you're commenting on Reddit:
human
Why are certain electrons only excited by specific wavelengths?

I was reading about why glass is transparent to visible light. The stated reason was that photons of visible light don't have enough energy to kick the electrons within the silicon atoms up to a higher orbital, so they instead pass through the atom.

Thinking about this from a chemistry viewpoint, this lines up with what I was taught.

But thinking about this from a physics/engineering standpoint, I'm a little confused.

Visible light is just an electromagnetic wave with a frequency of several hundred terahertz. Electromagnetic waves being a propogating electric field and magnetic field at 90 degrees to one another. Electrons are influenced by both electric and magnetic fields. 

So it doesn't make sense to me that an electromagnetic wave of a particular frequency would just be ignored by an electron. Surely even these frequencies that 'don't interact' with the electrons still impart SOME energy, right?

Can someone please shed some light on this for me?
gpt
Electrons obey quantum mechanics, and if you have a quantum system confined to some finite region of space (for example, atoms, or lattice sites in a crystal), there are quantized energy levels. That means that the electrons can only exist at certain discrete energies. So if you want to excite an electron from one state to another, you have to provide just the right energy to reach that higher state.

In reality since the system is constantly interacting with external electromagnetic fields, it’s not really a closed system, and it can be shown rigorously how that leads to energy levels not being infinitely sharp. There is some natural linewidth associated with each energy level, so if you supply the atom with 0.99E rather than E, where E is the energy required for some given transition, you may still observe the transition anyway. But that’s just a technicality, the important thing is that bound quantum systems have discrete energy levels.

Now if you take a macroscopic piece of material with several 10^(23) atoms in it, the levels get smeared out, and what you end up with is some continuous absorption spectrum, but you can still see remnants of the microscopic quantum structure in resonances in the absorption spectrum. While the material still absorbs light off-resonance, the absorption might go up by orders of magnitude on the resonance.