How is light formed, please help me!?

Question

I know how light is formed in a light bulb (not at all thoroughly though) and I have to find out how it forms with matches, fire, and the sun and stars. We haven't got our textbooks yet...

Answer 1

All photons are created (and destroyed) in interactions with electrons.

Answer 2

Both previous answers I believe are correct.

Additionally, light travels in the form of both Photon particles and Light waves.

Answer 3

Cosmo has it right enough.

To put some meat on the bones....

Electrons absorb the energy of photons to become more energetic electrons.  They can only do this though if the energy of the photon is exactly the right amount for the electron to make a transition from one of its allowable energy levels to another (electrons have to 'obey' these rules).

Similarly, when an electron changes from one of these 'allowable' energy levels to lower one, the difference in energy between the two levels is emitted as a photon.  If the energy of these photons is in a certain range we can see them because our eyes have chemicals in them that have molecules.. that have atoms.. that have electrons with just the right energy levels.  We can't see energy photons with higher or lower energy levels than this narrow range because the chemical in our eyes do not have electrons with the correct levels.

Electrons that release photons in this way are called bound electrons because they are stuck around the nuclei of atoms.  Electrons can also emit photons when they change direction.  This happens when there is a stream of electrons in a vacuum  and a magnetic field changes their direction.  Electrons that emit light in this way are called free electrons.

Torches, matches etc. all produce light with bound electrons.  Either electrical energy or chemical energy (as in matches) provides the energy for the electrons in the atoms to increase their energy levels.  After a very short time, the electrons drop back to the original levels and as they do, they emit the photons of light that you see.

All light generators on Earth use electrons as their source.  The contributor who mentions the sun is adding nuclear reaction 'to the mix'! The energy of all of the photons generated in the sun ultimately come form nuclear reactions.  Specifically, the so-called 'weak interaction'.  In these interactions, when say, two protons are forced together, excess energy is emitted as photons.  The excess energy has, rather like a garbage truck, to take away ALL the excess energy.  The amount of that energy corresponds to light that is more energetic than the the light we see, hence the gamma rays. Light generated in the core of the sun can take 150,000 to 200,000 years to make its way out because it gets absorbed and re-emitted countless times, often back in the direction it came from, so it is a long process.

Answer 4

While most light is due to interactions with electrons, it's not the whole story.  For example, in the core of the Sun, where fusion takes place, high energy gamma rays are released.  As i understand it, the plasma there doesn't have any electrons.