Question about photons

[khaled]

I'm just curious to ask ...

 

Since light is photons, I have some questions ..

 

1. Is the photon speed the same, among all photons ?

 

2. does the photon have any properties, like particles ?

 

3. In classical physics I learned that light is just waves, in modern physics it's a photon ..

where is the difference, where are we exactly .. matter, wave, energy ?

 

.. thanks

[timo]

1. Is the photon speed the same, among all photons ?

Yes for vacuum. Some people speak of photons in media like glass (which technically is a problematic statement). Since in media the speed of light can depend on the wavelength (which e.g. causes the spectral decomposition in a prism) so does the speed of those "photons".

 

2. does the photon have any properties, like particles ?

Yes. Mass (zero), electric charge (zero), color charge (zero), spin (one), momentum (depending on momentum ), energy (depending on momentum), velocity (depending on momentum), speed (speed of light), wavelength (depending on momentum), frequency (guess what that may depend on ...) spontaneously come to my mind.

 

3. In classical physics I learned that light is just waves, in modern physics it's a photon ..

where is the difference, where are we exactly .. matter, wave, energy ?

To keep it simple: Light indeed is just waves, except that there is some minimum amplitude ("height") for those waves. A photon is just a wave with the minimum amplitude. Larger amplitudes than the minimum one are created by adding up multiple minimum-amplitude waves (photons). There is a little bit more to it in reality, but I think the "minimum-amplitude wave" picture is already better than most laymen ideas about photons.

[IM Egdall]

I'm just curious to ask ...

 

Since light is photons, I have some questions ..

 

1. Is the photon speed the same, among all photons ?

 

2. does the photon have any properties, like particles ?

 

3. In classical physics I learned that light is just waves, in modern physics it's a photon ..

where is the difference, where are we exactly .. matter, wave, energy ?

 

.. thanks

 

 

1. As timo said, all photons travel at the same speed in a vacuum; about 670 million miles per hour.

 

2. Photons are a form of energy, and per Einstein's E=mc^2, energy (such as a photon) has weight and produces a graviational field just like mass does.

A photon is a massless particle. Its energy is proportional to its frequency (the higher the frequency the greater the energy).

 

3. Per modern physics, that is quantum mechanics, light (photons) behaves like a wave and like a particle.. So do electrons, quarks, neutrinos, atoms, and molecules! They all travel from place to place all spread out like a wave. We see this in the interference pattern they produce in a number of experiments, such as the famous double-slit experiment. But a photon, electron, etc. is detected in only a single location like a particle.

Edited August 31, 2011 by IM Egdall

[Klaynos]

2. Photons are a form of energy, and per Einstein's E=mc^2,

 

I would disagree here, photons have energy, they are not energy.