(Searched and although this has been asked before I still can’t find an answer that makes much sense to me)
So how does a photon come into existence, and how can it instantly be travelling at C? I turn on a light bulb and photons are instantly created and travelling at C…but created from what, exactly? The light bulb filament is in a vacuum, but every time I turn on the light bulb new photons are simply created out of nothing (with no “fuel” to draw from)?
I guess I’m struggling to understand how heating the filament results in billions (?) of photons in a constant stream travelling at C, when a millisecond earlier there was just an inert metal thread in a vacuum.
In: Physics
When an electric charge changes its direction of travel (accelerates), there’s a change in the local electric field which produces a magnetic field. As that magnetic field grows and then shrinks, it produces a corresponding electric field. These two interweaving fields are self-perpetuating and will continue to travel in the initial direction of the electric charge as fast as they possibly can, which happens to be light speed. Though it’s nothing more than a magnetic and electric field going back and forth, it’s distinct enough that we’ve given it a name: The photon.
When that photon is produced by the charged object’s acceleration, it takes a little bit of that objects energy away from it. That’s the “fuel” that you’re wondering about. Every light bulb, no matter how it works, is made of atoms or molecules. And, if you remember your high school chemistry, you’ll know that atoms and molecules have a dense nucleus with negatively charged electrons going around them.
In the case of an LED bulb, the electrons are given a tiny bit of energy that makes them go around the nucleus faster than usual. As the electrons go around the more energetic orbital, they accelerate, making them want to release that energy as a photon so that they settle into a more stable orbital that won’t allow them to lose any more energy.
With older incandescent bulbs, the atoms are simply heated up, making them jiggle in place as they collide with one another. Because they’re made of combinations of charged particles, they’ll release a photon every time they change direction from a collision, again removing a little bit of energy from the system.
This, by the way, is why particle accelerators have to be built larger to make the particles go faster. A smaller loop makes the particles accelerate more sharply, causing them to release photons and lose energy. Larger loops generate less acceleration, making the energy loss less pronounced.
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