# Microwave photons, when do they become real?

Gold Member

## Main Question or Discussion Point

A microwave oven produces microwaves that can heat food.

Can we consider the electromagnetic energy leaving the magnetron and traveling in the waveguide virtual photons and when the electromagnetic energy leaves the waveguide the electromagnetic energy "becomes" real photons? Or are they "real" once produced in the magnetron?

Thanks for any help!

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ZapperZ
Staff Emeritus
Virtual photons do not heat food or transmit signals.

Zz.

Gold Member
Virtual photons do not heat food or transmit signals.

Zz.
Real photons travel at c, energy in the wave guide travels slower then c, --> not real?

ZapperZ
Staff Emeritus
Real photons travel at c, energy in the wave guide travels slower then c, --> not real?
Since when does the group velocity of light defines if it is real or virtual? Do you even know what is a virtual photon?

Zz.

Gold Member
Since when does the group velocity of light defines if it is real or virtual? Do you even know what is a virtual photon?

Zz.
Can you give me a multiple choice test?

Nugatory
Mentor
Can we consider the electromagnetic energy leaving the magnetron and traveling in the waveguide virtual photons and when the electromagnetic energy leaves the waveguide the electromagnetic energy "becomes" real photons? Or are they "real" once produced in the magnetron?
There's no really good answer because we're using English to kinda vaguely talk our way around a concept that is most clearly expressed in the language of mathematics. So don't be too disappointed if no one comes up with a really clear answer.

But with that said, I'll give it a try. Wherever there is electromagnetic radiation, there are photons - real photons, not virtual ones. When one person says "the magnetron produces photons" and another person says "the magnetron produces waves", that's just two different ways of saying the same thing.

One pretty good rule of thumb though: Any time you find yourself reading about virtual photons.... If you don't also see a page full of equations, you're reading something that is oversimplified enough that you should think of it as a metaphor or an analogy, not a serious explanation of the way things really are.

Just to add to Nugatory's overall great post is that virtual photons are more like a math artifact to better suite our understanding of the world and the forces in it than a real particle.
If it would be real there would be separate detectors for virtual photons but there are no such things.You only detect real photons.

Even though as with any transmitter the microwave oven does have a far field and near field phenomenon I suppose.So @ Nugatory the magnetron produces photons one says, yes, other says it produces Em waves again yes but back to the first picture it does also produce virtual photons as they constitute a part of the near field.So there is electromagnetic radiation but according to what I just checked virtual photons included.
But then again are they in the near field because of the way we do our math or because they really are there , the answer would be the math.
I recall a thread here on PF in which i too took part that discussed these things.

Khashishi
The microwaves are real once they are produced by the magnetron.

Gold Member
From, "How Atom Smashers Work"

http://science.howstuffworks.com/atom-smasher4.htm

"The major structure of the particle accelerator is the copper tube. The copper tube has a strong vacuum inside through which the particles travel. The tubes are made of copper because copper conducts electricity and magnetism very well. At the SLAC linac, the copper tube is made of more than 80,000 copper cylinders brazed together for more than 2 miles (3.2 km)!

The copper tube is arranged to form a series of cells called cavities. The spacing of the cavities is matched to the wavelength of the microwaves. The spacing allows the electric and magnetic fields to repeat their pattern every three cavities. Electrons or positrons in the beam come through the cavities in small bunches. The arrival of each bunch is timed so that it gets a push from the electric field across the cavities. "

Ignoring any mistakes above, if I substituted the above system for the microwave oven in the top post are the microwaves accelerating the electrons just as real?

See diagram below.

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ZapperZ
Staff Emeritus
This is getting seriously off topic. You were told in many different ways of what is real and what is virtual. Somehow, you are refusing to accept them and continue to ask the same thing.

Zz.

Gold Member
This is getting seriously off topic. You were told in many different ways of what is real and what is virtual. Somehow, you are refusing to accept them and continue to ask the same thing.

Zz.
How do you rate the accuracy of the wiki article on virtual photons?

http://en.wikipedia.org/wiki/Virtual_particle

ZapperZ
Staff Emeritus