system
Given the following post, respond as if you're commenting on Reddit:
human
Can we see the emitted photons from atoms of the objects when the electrons of those atoms move to a lower energy level?

I have learned that things have colors when the electrons absorb the photons with particular wavelengths and the rest (photons that are not absorbed) will go to our eyes and make us see colors. And when the electrons lose energy they emit the photons which has the same wavelengths as when they’re absorbed. So my question is: Do we actually see the colors from the emitted photons? And if so it must change the color of the object, right?
This question has been bugging me for ages, please shed a light for me.
gpt
The answer is yes.  An electron moving from an excited state will emit a photon whose energy corresponds to the difference between the higher lever and the lower level.

The question of “color” depends on the energy difference between the states.  We usually talk of color as being a property of photons in the visible spectrum (human color), and there are plenty of instances where we can see the color when the electrons in a gas return to a lower state and the emission is in a wavelength our eyes can see.

The emitted photons are of an energy (and frequency, thus color) that reflects the energy gap from the high energy electron and the lower energy one.  Since the energy has to go somewhere, it’s spit out as light of a different color — where color reflects that amount of energy between the high and low states.

The vast majority of electron transitions don’t have color, in the common way we think about it.  Some of them are X-rays, which are very energetic and invisible to our eyes.  Some are much less energetic, again to the point we can’t see them.

In short, yes, we *can* see visible light from electron transitions.  But we can only see (with a naked eye) a tiny fraction of transitions that match that description.