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Judi
What difference can you think of between the photon and the electron?

 
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While both the photon and the electron are very tiny there is one key difference to them.

Have you started studying relativity?

If you haven't all you really need to know from this is that mass is actually not constant (as in classical physics). If one accelerates a small particle (because a big one is too hard to do) to speeds near that of the speed of light (denoted by c, equal to ~3x10^8 meters/second) you will find that it's observed mass increases with its speed. This is really hard to observe at everyday speeds though, to see a 1.00kg object increase its mass to 1.66kg you have to accelerate it to ~.8c. Now this is incredibly fast. In these terms traveling on the highway at a normal 65mph (or 105 kph) is only
.00000001c (amazing, right?).

This new variable mass as a function of speed spawned a few new terms. The phenomenon I described is called "variable mass" and to denote the difference between what mass you were describing we termed the "rest mass" of a particle to be its measured mass when it is not moving in your measured reference frame (it is impossible to make something absolutely not move, but that is a question for another day).

Now to the big cheese: what does all this stuff have to do with electrons and photons? Simple, an electron has a measurable rest mass of 9.11x10^-31kg while the photon has NO rest mass. It is either impossible to measure it or observe it. I'm not up to date or aware of any modern experiments that tried to slow photons down to 0 but I can't imagine them being very successful.

To reiterate (for those speed reading):
electron rest mass = 9.11x10^-31 kg
photon rest mass = 0 kg

Hope this helps!

Comments from Judi:
awesome!
Mr Robert Stevens IV USA
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1. Photon has absolutely no mass while electron has a definite mass.
2. Photon has no electric charge whereas electron has unit negative charge.
3. Photon has a fixed velocity - velocity of light which is constant. Electron
can be made to travel at various velocities, all less than that of photon.
4. Photon exhibits only the wave form while electron exhibits both WAVE FORM AND MATTER FORM.

Mr Joseph Vempeny India
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Hi There,

The photon is the packet or unit of light, usually thought of as a particle, but also having wave like properties. Photons have no mass, though they do contain energy, and all photons contain the same amount of energy.

The electron is a sub-atomic particle that carries a negative charge. When a lot of electron all flow in the same direction through a material (such as a metal wire) it gives rise to an electric current.

Journo
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