Photons?

[H2SO4]

Ive always been interested in light, but never realy understood it. Now i think its time i should understand it.

 

Here are my questions about light.

 

 

 

First of all, is a photon just like a part of an electron or something?

 

Second, why is it that they travel so incredibly fast? and why (according to einstein) can nothing exceed the speed of light. What makes them so special.

 

Im thinking there (maybe, energy) emitted from electrons as they fall back into their correct energy levels. Im thinking this because a LASER bumps a lasable (i.e. ruby) materials electrons out of order, then as they fall back, laser light is created.

 

And also, can photons collidide with other particles (you know, not like a wall, but like other forms of radiation or other photons). I was wondering all this because i got a green laser pointer and have been absolutely obsesed with it and all these questions started coming to mind.

 

If you can help, thanks.

[H2SO4]

I already saw the thread about wether electrons are energy or matter, and lets not turn this into the same argument. But ya, i know the laser thing is more complicated than that, but i was just throwing it out there.

[5614]

Photons are not electrons.

 

They travel fast because photons have no mass, so they are permitted to travel faster than objects with mass.

 

To accelerate an object with mass a force is needed, as the speed gets higher more force is required to accelerate the object further, if we continue this pattern eventually an infinite amount of energy would be required to accelerate the object any faster, this is the speed of light.

 

Photons are produced when an electron is excited, or gains energy, or jumps to a higher energy level, however it will almost immediately jump back down to it's original (lower) energy level, this requires the electron to lose energy, this energy is (because conservation of energy, energy can neither be lost or gained) released in the form of a photon.

 

Lasers work by exciting an already excited electron, this results in two photons being produced, these photons are synchronised and have identical wavelengths and phase, as seen here http://static.howstuffworks.com/gif/laser4.gif (I'm not using tags because it's a big-ish picture and you only need to see it once really!)

 

If you think about how much light there is in the air, photons must collide as some point, this doesn't mean they will interact with each other.

 

When a photon hits a wall or some such it excites the electrons in the atom (part of the wall) it hits, the electron will then de-excite releasing a photon, this is how we see the wall, and also the reason for colour, each atom will release a photon at a specific wavelength and frequency (it is the wavelength or frequency (which are indirectly proportional, ie. one gets bigger the other gets smaller) which dictates the colour we see the photon as).

 

There's lots more, ask questions and we can answer!

 

http://science.howstuffworks.com/laser.htm Is good for laser details.

 

Understand that light is not a wave AND a particle, that is merely a way of visualising it, photons are a single "thing" which exhibits properties of both a wave and a particle depending on how it is measured.

[H2SO4]

Ya, i completely understand the laser thing, and the wavelengths. Is that true that when photons hit a wall there exciting the electrons in the wall, so they produce light? I always thought they were being reflected (because we were always told that a black object reflects litttle light and obsorbs thge energy, where as a green object absorbs all wavelengths of light except green).

 

 

Oks, so when a photon is being "shot" out of an electron, its just automaticaly the speed of light? Now, from what i understand form what you have told me, it travels so fast because it's just energy. do other forms of radiation move this fast (gamma, x-ray, betta, ect)?

[Johnny5]

Ya' date=' i completely understand the laser thing, and the wavelengths. Is that true that when photons hit a wall there exciting the electrons in the wall, so they produce light? I always thought they were being reflected (because we were always told that a black object reflects litttle light and obsorbs thge energy, where as a green object absorbs all wavelengths of light except green).

 

 

Oks, so when a photon is being "shot" out of an electron, its just automaticaly the speed of light? Now, from what i understand form what you have told me, it travels so fast because it's just energy. do other forms of radiation move this fast (gamma, x-ray, betta, ect)?[/quote']

 

Gamma rays, and X-rays are photons, so they leave the emitter at c.

 

Beta particles are positively charged electrons, and leave the emitter at less than c.

[5614]

Gamma and x-rays are part of the electromagnetic (EM) spectrum... if you look here http://www.mhhe.com/physsci/astronomy/arny/instructor/graphics/ch03/0305.jpg it shows the EM spectrum, all of these are 'light' with different wavelengths/frequencies. So just like red is a lower frequency form of green, so radio waves are lower frequency form of gamma rays.

 

Light is "reflected" but technically it is being absorbed and re-emitted.

 

Yes it "just automaticaly" travels at the speed of light (the symbol for speed of light is c, so light always travels at c)

 

Beta, as in beta radiation, is a stream of electrons, these with their small mass can travel at almost the speed of light, but their mass stops them from getting there. Gamma/x-rays are part of the EM spectrum and are referred to (along with the rest of the EM spectrum) as electromagnetic radiation (EMR).

[5614]

Beta particles are positively charged electrons

umm, excuse me... WHAT!?!?

[parkinho]

Yes, visible light (along with gamma,x-rays, microwaves etc) is a small part of the electromagnetic (EM) spectrum and they travel at the speed of light, which in a vacuum is 300,000,000 m/s.

 

The colour of light photon depends on its energy, which is dependent on frequency (E = hf where h is Planck's constant). And of course, the higher the frequency, the shorter the wavelength (and vice versa)

[swansont]

Beta particles are positively charged electrons, and leave the emitter at less than c.

 

 

Beta particles are both positively and negatively charged. Electrons and positrons.

[H2SO4]

So what happens to the atom that emits a beta particle. Does it then give up a proton to balance it out?

[Nylex]

So what happens to the atom that emits a beta particle. Does it then give up a proton to balance it out?

 

If an electron is emitted, one of the atom's neutrons is turned into a proton. If a positron (a positron has the same mass as an electron, but is positively charged) is emitted, it is a proton in the nucleus that turns into a neutron. There's a whole page on beta decay here.

[5614]

Beta particles are both positively and negatively charged. Electrons and positrons.

Isn't that technically incorrect because beta is either positive or negative depending on whether it is electrons or positrons, it's not a bit of both, and if it is both (is it???) then surely you must define beta as either B+ or B- and you can't say a beta particle (a single particle) is both?!? (I know you said particles but people often talk about a beta particle)