What is light?

[scilearner]

Hello everyone,

 

I'm not studying about light so this question is just for interest. I know light is an electromagnetic wave. So this is my understanding of light. If there is a positive and negative charge, an electric field is created between them. If the charges oscillate this electric field oscillate and you get light if the wavelength is right. I don't know if this is wrong. My questions are

 

1. If electrons in the sun oscillate and produce light, what is the electric field in this situation? Between the electrons of the sun and the protons of the earth? Can't it interact with so many charges on its journey.

2. If photons are released with light do they travel from A to B or like sound does the wave propagate?

 

I'm not studying this area, so I only have you guys to ask.

 

Thanks

[Sisyphus]

Those are kind of huge questions, so if you're looking for complete understand you're really asking us to a write a book.

 

To put it very briefly, light can be produced in various ways. When the sun produces light, it is the result of atoms falling into lower energy states. e.g., an atom with a lot of energy has electrons in higher than the lowest possible orbital. When the electron drops back, a photon with energy equal to the difference in orbital energies is released.

 

2. If photons are released with light do they travel from A to B or like sound does the wave propagate?

 

Both. A photon is released at a single point and is absorbed at a single point, but it travels in the form of a wave.

[scilearner]

Those are kind of huge questions, so if you're looking for complete understand you're really asking us to a write a book.

 

To put it very briefly, light can be produced in various ways. When the sun produces light, it is the result of atoms falling into lower energy states. e.g., an atom with a lot of energy has electrons in higher than the lowest possible orbital. When the electron drops back, a photon with energy equal to the difference in orbital energies is released.

 

 

 

Both. A photon is released at a single point and is absorbed at a single point, but it travels in the form of a wave.

 

Thanks again for your time in helping me with my questions Ok as you said I can understand how photons are released from the sun, now if they are travelling why is their an electric field created? What is the electric field created between? Electrons in the sun and protons in earth? Thanks

[Mr Skeptic]

An accelerating charge produces an electromagnetic wave. In a classical electromagnetic wave, you have two components: a changing electric field, and a changing magnetic field. The changing electric field produces a magnetic field, and the changing magnetic field produces an electric field. It just keeps doing that as it moves along.

 

In quantum mechanics, the photon is considered a massless particle.

[scilearner]

An accelerating charge produces an electromagnetic wave. In a classical electromagnetic wave, you have two components: a changing electric field, and a changing magnetic field. The changing electric field produces a magnetic field, and the changing magnetic field produces an electric field. It just keeps doing that as it moves along.

 

In quantum mechanics, the photon is considered a massless particle.

 

Thanks for the response However what is this electric field created between? Which charges? Why does it change?

[Mr Skeptic]

No electric charges are needed to create an electric field, any more than you need magnetic charges (which don't exist) to create a magnetic field. The change in one field (electric or magnetic) is due to the change in the other field.

[scilearner]

No electric charges are needed to create an electric field, any more than you need magnetic charges (which don't exist) to create a magnetic field. The change in one field (electric or magnetic) is due to the change in the other field.

 

I don't understand. Isn't electric field created between two opposing charges? How is it created otherwise? Thanks

[Mr Skeptic]

By induction (look it up).

[scilearner]

By induction (look it up).

 

Ok I'm reading it right now. I have just have few questions though.

 

1. Is light the disturbance of an already existing electric field?

2. If change of magnetic flux induces electric field, how do you know which one came first?

3. How does a photon create a change of magnetic flux?

[swansont]

Ok I'm reading it right now. I have just have few questions though.

 

1. Is light the disturbance of an already existing electric field?

2. If change of magnetic flux induces electric field, how do you know which one came first?

3. How does a photon create a change of magnetic flux?

 

1. No. You can have photons where there is no previously existing field.

2. You don't, unless you have more information.

3. It doesn't. A photon can be the result of a change in the magnetic flux, but it doesn't cause it, per se.

[scilearner]

1. No. You can have photons where there is no previously existing field.

2. You don't, unless you have more information.

3. It doesn't. A photon can be the result of a change in the magnetic flux, but it doesn't cause it, per se.

 

Then how does light create an electric field? I read about induction and I can't understand how to relate it to this. Thanks

[swansont]

Then how does light create an electric field? I read about induction and I can't understand how to relate it to this. Thanks

 

It's more that light is an oscillating E and B field.

[scilearner]

It's more that light is an oscillating E and B field.

 

Thanks for the reply Skeptic said that you don't need charges to create an electric field.

 

Wiki:electric field is a property that describes the space that surrounds electrically charged particles or that which is in the presence of a time-varying magnetic field.

 

So is charges involved or not in this.

 

EDIT: If light is an oscillating electromagnetic field? How is the electric field it oscillates created?

Edited April 23, 2010 by scilearner

[Mr Skeptic]

EDIT: If light is an oscillating electromagnetic field? How is the electric field it oscillates created?

 

As far as I know, the only way is to start with accelerating electric charges (typically an electron), and once the wave is started it is self-sustaining.

[swansont]

You can also get EM radiation via atomic (i.e. electron) or nuclear transitions or annihilation of a particle/antiparticle pair.