# How can a photon move an electron if it has no mass?

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I’m trying to understand how a solar panel works but I’m having trouble. How can something with no mass move something with mass?

In: Physics

Tldr: the object causing the electrons to move is actually a distant electron in the light source. The photon is basically the “force”

A photon is actually a disturbance in the electric/magnetic field. It has more in common with a FORCE, not an object.

An electron can cause another electron to move without touching it using an electric field. So an electron the light source shifted. This means other electrons will be shifted as it’s electric field is now over there. This shift in the field travels outwards, very quickly, as a light wave (or photons). When it reaches the distant electrons they shift and jiggle in response.

Photons are little packets of energy that electrons absorb. It doesn’t *move* the electron so much as energizes it into a higher energy state. There really isn’t a good analogy, it’s just how photons work. When electrons absorb a photon, they move up in their energy levels – essentially, a higher “orbit” around their atomic nuclei.

Solar panels work by putting together materials so that there’s a sandwich of three things: a side with slightly too many electrons, a side with slightly too few electrons, and a material in the middle that doesn’t conduct electrons very well but *can* under certain circumstances.

Photons hit the side with slightly too many electrons, which energizes them into a higher “orbit” which is a bit farther away from the nucleus. That means the nucleus can’t hold onto the electron quite as well – the electron is normally attracted to the positive protons in the nucleus, but the farther away the electron is, the less force there is pulling it towards the protons.

So the electron is already kind of precariously whizzing around the nucleus, not held down super well. When it absorbs a photon and moves even farther away from the nucleus, it’s really not being held by that nucleus much at all. That won’t automatically make an electron leave, though, because the electron doesn’t have anywhere to go. That’s what the other side with slightly too few electrons is for. That energized electron now has somewhere to go, that has a slightly positive pull (because there are protons without matching electrons). So, poof, it zips across that semi-conducting barrier and *flows* to the other side.

That creates a new hole where the electron used to be, so a new electron jumps into that hole. *That* electron leaves a hole, so an electron behind it jumps into *that* hole, and so and so forth so that when you connect the two sides of the solar panel material sandwich, you get get a circle of electrons getting bumped across the barrier and pushing each other into the empty spots left by those electrons.