What is a photon?

Is it just a form of energy or is it a particle? I've never found out what it really is.

this is from the online encyclopedia britanica.

"Photon - Minute energy packet of electromagnetic radiation. In 1900 M. Planck found that heat radiation is emitted and absorbed in distinct units, which he called quanta. In 1905 A. Einstein explained the photoelectric effect, proposing the existence of discrete energy packets in light. The term photon came into use for these packets in 1926. The energies of photons range from high-energy gamma rays and X rays to low-energy infrared and radio waves, though all travel at the same speed, the speed of light. Photons have no electric charge or rest mass and are the carriers of the electromagnetic field."

Hope this sheds some light for you.

Yes, Yes... I already know about the quanta thing, but I'm not sure if it mean's it's nothing but energy or a particle.

Hmm god I had a brain fart, I know on the tip of my tongue what they call this.

Is it..."Particle-wave duality" or is it simply "partical duality" plurality what? TN1 help me out here

Anyways...it's both. In some ways it behaves as a particle in others it behaves as a wave and in both cases there's formulae and experiments that show both are true.

It is litterally both a wave and a particle at the same time, at least this is true with the electron I'm most certain it is with the photon HOWEVER!

If I'm to be less mistaken in this statement: They do not know about the photon.

I think last I heard they weren't sure if it was a wave "Electromagnetic radiation" or a particle "photon" or a bit of both, I think I saw once a show on this.

They did an odd experiment...where they had something like to verticle slits in a card, and shone a focused light through them, where instead of on the wall opposite, where you'd think there would be two slits of light, there were many slits of light.

In effect this showed that it was a wave (I think) and then of course there's probably something saying it's a particle too.

I think it's that duality thing, but maybe I'm wrong and they aren't sure yet.

Sincerely,
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Everything propagates like a wave and exchanges energy like a particle .
A photon obeys the particle-wave duality ,so it can be assumed to as a wave and a particle at the same time !
Light is made up from massless particles called photons .
But photons and light can be expressed as waves .Light is part of our electromagmetic spectrum ,therefore photons are electromagnetic radiation .
The other parts apart from the visible part of spectrum are:Ultra-violet,infa red, microwaves ,X-rays radio waves,gamma rays.
The energy is coming to us in the form of packets or quanta therefore is said to be quantised !
I will give you the reason for that.The energy
E=n^2 p^2 h^2/2mL^2.This is the formula for the energy.
As you can see h is just the Planck's constant,p is the greek pi or 3.14 (another constant), m is the mass of any given particle ,L is the region that it is confined.But n depends on the energy level that the particle is .For example for n=1 then n^2=1 ,but for n=2 then n^2=4 .Therefore because of the term n^2 we cannot have values like n^2=3 , why is that??Because simply
n=1,2,3,4.... Only integers....

Maybe your problem is in your question.

Einstein found out that energy can form mass and vice verse (or so they believe and are testing in labs).

It may be a matter of appearance for photons. They act like a wave and a particle, but they are probably different sides of the same coin.

Is a photon a wave or particle? Both. It is probably a matter of perspective or positioning.

Wait TN1 that forumla can't be right for the Energy of a photon though...photons have no mass and anything over zero is undefined or whatever...

I thought the energy of a photon was different like Ep=hc/L where h is Planck's Constant c the speed of light and L lambda or the wavelength of that light, hence showing it's "Wave properties" versus its partical-like properties which is displayed in other ways...?

Yeah...quantised, that deals with photons too I suppose but so far I only know of electrons and their "quantum levels" Maybe the formula you gave was for the energy of an electron? Or is it the energy for any particle?

Except I still don't see how it can include the photon though, which is supposed to not have any mass...which is an interesting aspect because that means Energy does not have to be dependant on mass!

Ahh my mind has gone numb over the winter, and is sorta waking up so everything simple is like a revelation to me...heh

Sincerely,
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[Edited on 12-1-2003 by FreeMason]

The photon problem (as it is still not completely understood) is not whether it is a particle or a wave (from an energy source). The problem lies in creating an explanation which can be properly understood, and can be summed up in this: The photon sometimes behaves like a particle, and other times, behaves like a wave, so what is it?

In effect, the answer to the question, What is a photon?, has not been fully uncovered. However ironic it may be, research over the past century has been able to learn much about the photon and formulate theories and equations that are proven perfectly effective in predicting the behaviour of photons and related observations without actually knowing what a photon exactly is. This isn't a problem though, since science (particularly physics (even more particularly, quantum mechanics)) does this all of the time. Even if the question is never answered, what is known regarding photons is still valuable in physical research and related theories.

What about the supposed "gravitons"?

Here's a simple site explaining a bit of it. I hope this helps.

newton.dep.anl.gov...

Photons are emmited or absorbed when electrons move from one energy level to another.What i gave you is the predicted energy of an electron in different energy levels ,this is the expression of a particle in a box ,coming from the simple solution of schrodingers equation ...
The formula E=hf=hc/L is just the energy of the photon when you know the wavelength or the frequency....

Yes TN1 admit it I was correct!!!!

When you were talking about the energy in your other post, you were "suggesting" that it was the energy of the photon, you didn't actually state what it was the energy of, but it was only of the electron. However they are closely related, oh well, it's too early to be discussing this all yet, soon enough though...soon enough

Also man...do you know of any theories that try and explain Gravity as a form of energy?

For instance, I'm beginning to think Gravity is not the attraction of mass, but rather the "want" for all particles to achieve only potential energy...therefore when a partical is "elevated" it has kenetic energy it wishes to release by "falling".

This doesn't really yet explain why it has kenetic energy just for being raise, nor does it yet explain why things orbit blah blah....but then we really don't know how gravity affects Space yet, or rather how Space affects Gravity so maybe Space plays an important roll in this, as in Space is purely potential energy....while all mater has some kenetic value and hence large quantities tend to attract or orbit and such.

Anyways...think about it

Sincerely,
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Of course, it simply states "We don't know" in a prettier way, hehe....

A better Question to ask is what is white light energy. Knowing that a all matter contains or appers to contain White light energy is somthing that needs to be explored more. If the Wavelength freqs could be identifed white light energy in theory could be produced. Just think what could be accomplished if that knowledge was known.

This is all that I have to say about this subject this is my 2 cents on this issue.

Falcon

Very good idea !
You know that every colour has its own wavelength,for example the visible part of spectrum corresponds to a range between 300-650)nm .I don't know if you are familiar with the international system of units but by the way nm means nanometers. A nm=10^-9 m ,so it is actually a very small length compare to the lengths we experience every day!
Now as you move in the visible part of spetrum the wavelength increases and the frequency decreases according to the formula c=Lf .Where c is the speed of light which is a constant (it is actually a constant ,not as others claim in various posts),f if the frequency and finally L is the wavelength .
From the violet part of the spectrum with L almost 300nm, to the red part of spectrum (600nm),we have a range of energies E=hf .Therefore the energy depends on the particular frequency and wavelength of the radiation.
White light now is created if we mix all the colours (visible) and produce a unique one.Have you ever heard about Newton's disk??Is just a disk with all the colours that when you start spinning it fastly the white colour is produced.
Therefore the white colour has a unique energy and wavelength since it is part of the visible spectrum and has probably energy and wavelength between (300-650)nm.I am not guite sure what is the numerical value ,but it will probably depend on how many colours are there at the first instance.

Ehmmm, TN1

It's actually our stupid eyes that produce the sensation of white light. It is an ensemble of colours that all combined deliver you the sensation of white. People working with HTML might have noticed that colours can be defined as the brightness of red, green and blue combined. Our eyes have receptors that are most sensative to these colours but these receptors add up their values to produce the colours that we "see".

You know!

I'm doing by physics at college at the moment and you've just answered my question i was stuck on?
Cheers everyone, i owe ATS one!

ps,

If your still confused, watch Stargate Sg-1 and listen to Major Carter (Amande Tapping), she their resident Theoretical Astrophysicst!

You are right Devil's advogate ,but i gave a physical explanation of the different colours and their mixtures ..You know,different wavelenghts-different colours.
It is true that our eyes are sensitive and can peak only certain types of wavelenghts(visible part) ,so we cannot see the infared.