Like I understand light is photons. But from whence the photons? How come if I’m in a dark room (by the way, why is the room dark? Why no photons in the room?) and I turn on a flashlight, suddenly there’s photons everywhere?
In: Physics
Photons are little bundles of electro-magnetic energy of that operate both as waves & particles. Depending on the amount of energy in the photon, it will vibrate with a different frequency/wavelength and that frequency/wavelength will determine what kinds of matter it can interact with. A small subset of photons have the right frequencies/wavelength to interact with the photo-receptors in our eyes and these photons get referred to as visible light.
So if you are in a dark room, there are lots of photons flying around, but it’s dark because those photons don’t have the right wavelength to light up your eyes. Devices like flashlights are specifically designed to release photons in the visible spectrum so that we can see.
Electrons want to exist in stable configurations known as “energy levels” and when an electrons has too much energy, it release some as photons. This means that when you apply energy into a system, you can make electrons release photons in specific ways. Here are a couple of examples:
1) When a flow of electrons are forced to move through the filament of a tradition light bulb, they transfer some their energy to the filament, which gets turned into a bit of thermal energy (heat) and released as light.
2) When a flow of electrons are forced to move through a LED (Light Emitting Diode), they transfer some of their energy to diode where it gets released as light.
3) Phosphorescence. This one is actually really neat. When the electrons in certain substances absorb photons from the environment, they temporally shift up a partial energy level and stay there for a bit of time before releasing a photon and returning to their original energy level. This is why some substances will light up if you shine a light on them.
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