# What is the range of electric field of an photon?

Obviously every electric field has an specific range upto which it can have effect on.What is the range from the median line for an electric field of a photon.As most physics textbooks and physicist visualize the electric field of an photon as straight line and also the electric field has only one electric field strength at an instant.How this visulaization affect the range.Does it have effect on particles on the left and right side of the straight line that we visualized.This may be a bizzare question,but we got to understand everything about it to manipulate it.So please give your best opinions,Thank you.

Photons carry no electrical charge. For objects like electrons which are charged, their field lines extend to infinity.

• But their field strength drops,photons doesn't carry no electrical charge but they contain electric field and as electric field drops by a factor of 1/r(squared),it has a a specific range where it can have effect on.Same is for an electron,field lines are imaginary.I am asking upto what distance the electric field can have effect on a charged particle. – Anns Jul 17 '18 at 7:19
• any force field that goes as 1/r^2 has infinite range. the effects get small, but they never go to zero. – niels nielsen Jul 17 '18 at 15:49

The photon is a zero mass elementary point particle in the standard model of particle physics. It has no extent, and the only measurable quantities it has are a spin , + or - to its direction of motion, and its momentum/energy, since its mass is zero.

What is the range from the median line for an electric field of a photon.

The photon does not have a volume or a real electric field attached to it, so

As most physics textbooks and physicist visualize the electric field of an photon as straight line

this is wrong.

and also the electric field has only one electric field strength at an instant.

and this is also wrong.

The photon as a point particle travels in straight lines and when it interacts it interacts at a point, as can be seen in this double slit single photon at a time experiment, Single-photon camera recording of photons from a double slit illuminated by very weak laser light. Left to right: single frame, superposition of 200, 1’000, and 500’000 frames.

But also the photon is a quantum mechanical entity, and it has a wavefunction

which gives the probability distribution in (x,y,z,t) to see a photon interacting. The interference pattern seen is the complex congjugate square of the probability distribution for the single photons to interact with the double slits, and that does have in its complex definition the E and B fields that zillion such photons wavefunctions, superposed, will generated the classical light beam, with its E and B fields.

So in the sense of probabilities, a photon will have a range given by the superposition with other photons.

How classical fields originate from the quantum mechanical understructure can be studied here given quantum field theory knowledge.

I cannot answer the emergent question: "how close must two photons be in spacetime in order to produce a classical beam by superposition", as this is the only question that can have some answer as far as photons and fields go.

• All i am trying to ask is upto how much distance will the particles feel the photon.if r is the distance of particle from a photon then what is the maximum value of r. – Anns Jul 17 '18 at 11:19
• It depends on the quantum mechanical interaction crossection. these are usually calculated in energy momentum space. for space one can use the estimate of the Heisenberg uncertainty principle ΔxΔp>h/2π to give a probable distance estimate for a given momentum, where quantum mechanical probabilities reign and one can talk of photons. when energies and distances fulfill the HUP then one is in the classical light regime, not photons. – anna v Jul 17 '18 at 14:24

Physics theories give conflicting visualizations of light and particles, which is often frustrating to students.

In geometrical optics, lights are rays.

In classical electromagnetics, light is a wave. Like Niels Nielsen wrote, there is no charge of a propagating wave electromagnetic wave.

In quantum mechanics, light is a particle, a photon. I think Anns may be asking about the shape of that particle, and its ability to interact based on proximity to other particles, yes? Well, in quantum mechanics there really is no physical model of the photon.

In quantum field theory, the relativistic extension of quantum mechanics, photons are discrete excitations in a quantum field. Particle collisions have a "cross section" (you can read up on this, if this is what you are getting at) determining the probability of interaction. This cross section is sometimes thought of as a physical width, but it depends on the combination of particles.