# How do photon particles travel through glass?

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Been studying science in college for about 2 years and this simple question has me questioning my own IQ. I understand how light travels through different mediums but photons are particles right? Actually physical particles that can travel through solid blocks of glass?

I dont know if Im just stupid or my teacher doesnt care, this question could keep me up at night.

In: Physics

Photons are not *only* particles, they are also waves. You’ve probably heard that most of an atom is empty space. That’s *sort of* true. Electrons don’t “orbit” the nucleus in the sense of a tiny particle whizzing around the nucleus – electrons are *also* also waves. They exist in a “cloud” of probability around the nucleus where they *can* be in any position and behave in many ways as if they are in *every* possible position.

A photon will pass through these clouds of probability and interact with the electrons there.

Photons give electrons energy, energizing the electrons and moving them into a higher state around the nucleus. The more energy a photon has, the higher the energy state of the electron after it absorbs a photon. For quantum mechanics reasons, electrons can’t exist halfway between states. They are either all the way into the higher state or not at all. Think of it like an elevator that can’t stop halfway between floors.

Also for quantum mechanics reasons, these energy states can only have so many electrons in them. If the energy state is full, an electron *cannot* move into that state.

If a photon doesn’t have enough energy to move the electron *all the way* into an *empty* energy state, the photon cannot be absorbed by the electron and it will pass right through that electron cloud.

Glass and water and stuff that is transparent to visible light is transparent because the electrons are all arranged to fill up the energy states so that no photons in the visible part of the spectrum have enough energy to move any of the electrons all the way into the next empty state. Therefore, none of those photons can be absorbed and they go right through.