Can the light create electromagnetic field?

[scientist91]

Very briefly, electrons in a metal can have certain energy levels that fall in the conduction band. These electrons can 'hop' from atom to another to make a current. But it's not as simple as classical particles moving. You need quantum mechanics to understand it properly, which I don't claim I do.

Ok, thank you.

 

[scientist91]

There must be some movеment of the electrons, when is in question the impact of the light on conductor.

 

[scientist91]

Is there any small current in conductor with circular closed loop impacted by the light?

 

[ZapperZ]

There's plenty! Search for loop pickup!

Zz.

 

[scientist91]

Can somebody explain better?

 

[rbj]

Can somebody explain better?

look at it this way, 91: imagine that you and i are standing some distance apart and facing each other. you're holding a positive charge and i am holding a negative charge and that we both are restricting our charges so they cannot move toward each other but they can move up and down and left and right (just not forward or backward). so i move my charge up a meter. since your charge is attracted to mine, your charge also wants to move up a meter and you allow that. then i move it down and your charge follows it down. now i move it to my right (your left) and your charge moves toward your left. then to my left (your right) and your charge follows it.

now i move my charge up and down repeatedly and your charge follows it up and down. that is an electromagnetic wave that originated with me moving my charge around and that wave moved toward you (at the speed of propagation of E&M waves which is "c") and caused your charge to move. in a very real sense, my moving charge is a "transmitting antenna" and your moving charge is a "receiving antenna". if, somehow, i could move my charge up and down a million times per second, you could tune your AM radio to 1000 kHz and hear a signal (a silent carrier). if i could move it up and down 100 million times per second, you could tune it in with your FM radio just between the 99.9 and 100.1 settings (provided no other stations were close by). if i could move it up and down 500 trillion times per second, you would see it as a blur of orange colored light. now i can't move it up and down an entire meter 500 trillion times per second because the speed of that movement would exceed c. but i can have a whole pile of like charges and move them up and down maybe 10 microns at a frequency of 500 trillion Hz. that is what happens in a transmitting antenna.

that is what light is (from a wave-property perspective) and it required no medium for these waves to travel. they just are there because unlike charges attract and like charges repel - there need be no medium in between for that to happen.

there are other phenomena that light exhibits that make it appear like it's made up of particles (such as the photo-electric effect). seems like a contradiction, but both behaviors are exhibited by light and all the physics is, is an attempt to coherently describe and explain both demonstrated properties. light, which is EM radiation at about 500 GHz, has both wave-like and particle-like behavior.

 

[scientist91]

look at it this way, 91: imagine that you and i are standing some distance apart and facing each other. you're holding a positive charge and i am holding a negative charge and that we both are restricting our charges so they cannot move toward each other but they can move up and down and left and right (just not forward or backward). so i move my charge up a meter. since your charge is attracted to mine, your charge also wants to move up a meter and you allow that. then i move it down and your charge follows it down. now i move it to my right (your left) and your charge moves toward your left. then to my left (your right) and your charge follows it.

now i move my charge up and down repeatedly and your charge follows it up and down. that is an electromagnetic wave that originated with me moving my charge around and that wave moved toward you (at the speed of propagation of E&M waves which is "c") and caused your charge to move. in a very real sense, my moving charge is a "transmitting antenna" and your moving charge is a "receiving antenna". if, somehow, i could move my charge up and down a million times per second, you could tune your AM radio to 1000 kHz and hear a signal (a silent carrier). if i could move it up and down 100 million times per second, you could tune it in with your FM radio just between the 99.9 and 100.1 settings (provided no other stations were close by). if i could move it up and down 500 trillion times per second, you would see it as a blur of orange colored light. now i can't move it up and down an entire meter 500 trillion times per second because the speed of that movement would exceed c. but i can have a whole pile of like charges and move them up and down maybe 10 microns at a frequency of 500 trillion Hz. that is what happens in a transmitting antenna.

that is what light is (from a wave-property perspective) and it required no medium for these waves to travel. they just are there because unlike charges attract and like charges repel - there need be no medium in between for that to happen.

there are other phenomena that light exhibits that make it appear like it's made up of particles (such as the photo-electric effect). seems like a contradiction, but both behaviors are exhibited by light and all the physics is, is an attempt to coherently describe and explain both demonstrated properties. light, which is EM radiation at about 500 GHz, has both wave-like and particle-like behavior.

But is there any small current or something? And can the light itself to be current, because it have part of electric and part of magnetic field?

 

[Mentz114]

But is there any small current or something? And can the light itself to be current, because it have part of electric and part of magnetic field?

The electric and magnetic fields in EM radiation are sourceless. There is no charge, therefore no current. The electric field can induce a current in an antenna. Read rbj's post carefully.

 

[Xezlec]

But is there any small current or something? And can the light itself to be current, because it have part of electric and part of magnetic field?

Current means charges moving. Light = fields moving, but not charges moving. When light hits a conductor, there is a tiny current.

 

[scientist91]

Current means charges moving. Light = fields moving, but not charges moving. When light hits a conductor, there is a tiny current.

Ok, I understand, but what is the shape of the magnetic field of the electron? Can that electron be excited of its own magnetic field?

 

[scientist91]

and how do the electrons release their excess of energy (in conductor with current)? Do they release their energy in form of photons and get back to their orbitals?

 

[scientist91]

It's hard to explain in such simple language. Pick up a spring. Hold it by one end. Move it up and down slowly. Now try moving it faster, and faster, and faster. Eventually the spring won't bounce very much anymore because you're shaking it too fast. It can't keep up.

Electrons have mass, and they also have other things "holding" them. They are stuck in a "soup" of other electrons, so they can't just move as fast as you want.

So they will stop moving right?

 

[scientist91]

look at it this way, 91: imagine that you and i are standing some distance apart and facing each other. you're holding a positive charge and i am holding a negative charge and that we both are restricting our charges so they cannot move toward each other but they can move up and down and left and right (just not forward or backward). so i move my charge up a meter. since your charge is attracted to mine, your charge also wants to move up a meter and you allow that. then i move it down and your charge follows it down. now i move it to my right (your left) and your charge moves toward your left. then to my left (your right) and your charge follows it.

now i move my charge up and down repeatedly and your charge follows it up and down. that is an electromagnetic wave that originated with me moving my charge around and that wave moved toward you (at the speed of propagation of E&M waves which is "c") and caused your charge to move. in a very real sense, my moving charge is a "transmitting antenna" and your moving charge is a "receiving antenna". if, somehow, i could move my charge up and down a million times per second, you could tune your AM radio to 1000 kHz and hear a signal (a silent carrier). if i could move it up and down 100 million times per second, you could tune it in with your FM radio just between the 99.9 and 100.1 settings (provided no other stations were close by). if i could move it up and down 500 trillion times per second, you would see it as a blur of orange colored light. now i can't move it up and down an entire meter 500 trillion times per second because the speed of that movement would exceed c. but i can have a whole pile of like charges and move them up and down maybe 10 microns at a frequency of 500 trillion Hz. that is what happens in a transmitting antenna.

that is what light is (from a wave-property perspective) and it required no medium for these waves to travel. they just are there because unlike charges attract and like charges repel - there need be no medium in between for that to happen.

there are other phenomena that light exhibits that make it appear like it's made up of particles (such as the photo-electric effect). seems like a contradiction, but both behaviors are exhibited by light and all the physics is, is an attempt to coherently describe and explain both demonstrated properties. light, which is EM radiation at about 500 GHz, has both wave-like and particle-like behavior.

tell me what actually happens? Why with the high frequency there can't be induced current? In normal magnetic field when you move the magnet from the on side of the coil that is + and from the other side - and when you pull back the place where the + was now is - and the place where the - was now is +. So with high frequency the + and - can't change so fast or what?

 

[rbj]

tell me what actually happens? Why with the high frequency there can't be induced current? In normal magnetic field when you move the magnet from the on side of the coil that is + and from the other side - and when you pull back the place where the + was now is - and the place where the - was now is +. So with high frequency the + and - can't change so fast or what?

i really don't understand your question. i didn't say anything in my simplistic thought experiment about moving or stationary magnets. i was talking only about electrostatic charges and actions.

and no one, other than you, are saying that high frequency changes in magnetic fields do not induce an electrical voltage (which will result in a current if the loop is closed). so i don't accept your premise, and thus cannot answer that specific question.

now magnetic effects can be thought about in two manners: probably the most fundamental way to think about it is that magnetic effects are nothing other than the electrostatic action, but taking into consideration the effects, as we perceive such effects, of special relativity. magnetism is not a new or separate force, but it is a manifestation of electrostatic forces (with special relativity also considered).

the other way to think about it, is with classical physics, which is what Maxwell's equations are. so here, magnetic actions are differentiated from electrostatic actions and that is described and quantified in Maxwell's equations. a changing electrostatic field (with respect to time) will generate this magnetic field and a changing magnetic field will generate an electrostatic field. since sinusoidal functions can be differentiated forever (to whatever order of derivative) and not go to zero, it stands to reason a sinusoidal source (either electrostatic or electromagnetic) will produce a disturbance that will continue on forever. and that any changing magnetic field (that you get when you move the magnet in and out of the coil) will produce an electostatic force (that we call a "voltage").

i don't have the time nor the expertise to replace a good classical E&M course that you would get in a physics department in college. so this is about as good as i can do to answer you.

 

[scientist91]

So why there is induced current with very low voltage and not high? Is the kinetics energy fault of the slow speed of moving of the electrons?