Maxwell's electromagnetic theory of light

[copernicus1234]

I was looking a physics book and noticed that Maxwell's electromagnetic theory of light is based on Ampere and Faraday induction experiments yet induction is not optical. Can someone explain this to me. I Having a hard time figuring this out. Maybe someone who is smart could explain this to me there must be an explaination since Maxwell's theory has been around for over 150 years, as I am told.

[ACG52]

It's not a theory of light, it's a theory of the electromagnetic field.

[ajb]

It's not a theory of light, it's a theory of the electromagnetic field.

....and light happens to be a form of electromagnetic radiation.

[Orodruin]

So to summarize and put it plainly: Maxwell's theory is not only a theory of how light behaves but of how electromagnetic fields behave and interact with matter. Since light is a form of electromagnetic radiation it is described by Maxwell's theory. However, it is not based on optics and any typical textbook on the subject is not going to start from there but probably from static configurations. Once dynamic fields have been reached, optics will follow from the theory. This is why the book does not start by discussing optics.

[copernicus1234]

Maxwell book has a section titled "ELECTROMAGNETIC THEORY OF LIGHT" (Maxwell, part IV).

 

 

 

Maxwell describes polarization using transverse waves of light; therefore, Maxwell's electromagnetic theory of light is use to describe how light behaves. Also, Maxwell's equations are also derived. In addition, to induction not being optical there the highly vexing question of the continuity of the electromagnetic induction field that appears, for all extensive purposes, to be continuous which conflicts with Lenard's photoelectric effect that proves light is composed of particles. Wouldn't it be kinda nice if a new level of physics was discovered and we could go to infinity and beyond!

 

 

 

Also, ajb....do they have extra large polish hotdog in Poland? And do Polish women have similely faces?

 

 

 

 

 

Maxwell, James. Dynamical Theory of the Electromagnetic Field. Royal Society Transactions. Vol. CLV. 1864.

Edited May 6, 2014 by copernicus1234

[swansont]

Maxwell book has a section titled "ELECTROMAGNETIC THEORY OF LIGHT" (Maxwell, part IV).

 

 

 

Maxwell describes polarization using transverse waves of light; therefore, Maxwell's electromagnetic theory of light is use to describe how light behaves. Also, Maxwell's equations are also derived. In addition, to induction not being optical there the highly vexing question of the continuity of the electromagnetic induction field that appears, for all extensive purposes, to be continuous which conflicts with Lenard's photoelectric effect that proves light is composed of particles. Wouldn't it be kinda nice if a new level of physics was discovered and we could go to infinity and beyond!

 

They did discover new physics, called quantum mechanics, several decades after Maxwell did this work.

[Mike Smith Cosmos]

I was looking a physics book and noticed that Maxwell's electromagnetic theory of light is based on Ampere and Faraday induction experiments yet induction is not optical. Can someone explain this to me. I Having a hard time figuring this out. Maybe someone who is smart could explain this to me there must be an explaination since Maxwell's theory has been around for over 150 years, as I am told.

As far as I am aware. I had to learn it in UNI, Maxwell did all his sums from magnetic fields, and electric fields. They are a bit perculiar sums ( sort of summing up around the complete circle around the field , [A] for magnetism , and for electric field , then a bit of jiggery pokery maths ) but none the less the sums came out with a speed for electro magnetic waves. He was aghast that this speed was the same as the speed of light , previously known. He then deduced from this similarity : " Thus light must be electro-magnetic waves" , that was previously not known . They( people/scientists prior to Maxwell) believed something like light was , something else, name escapes ( corpuscles I think ! )

 

So Maxwell was the one to describe light as electro- magnetic waves !

 

Mike

Edited May 6, 2014 by Mike Smith Cosmos

[copernicus1234]

Mike..............."So Maxwell was the one to describe light as electro-magnetic waves"

 

 

True, but that does not justify Maxwell's electromagnetic theory of light that is based on Ampere and Faraday induction experiments that are not optical.

 

 

swansont............. "They did discover new physics, called quantum mechanics, several decades after Maxwell did his work"

 

 

copernicus1234.................Quantum mechanics is based on Planck's blackbody derivation that is justifying Maxwell's electromagnetic theory of light. Most of Modern physicst is based on Maxwell's theory. In addition, the derivations of the EM wave equations of light, using Maxwell's equations is patently incorrect, unless you believe in scalar electromagnetic field theory. The Polish Susage.

Edited May 6, 2014 by copernicus1234

[Mike Smith Cosmos]

Mike..............."So Maxwell was the one to describe light as electro-magnetic waves"

 

 

True, but that does not justify Maxwell's electromagnetic theory of light that is based on Ampere and Faraday induction experiments that are not optical.

 

.

Well as far as I understand it : people like Hertz , we're playing around with sparks, and induced sparks across the room. Marconi was using this to develope transmission of these " effects" , Young was fiddling about with corpuscles of light, and Maxwall was doing maths on amperes magnetic fields and at the same time linking in the field lines of electric fields of Michael Faraday. He did all his perculiar sums , and came up with his equations. NOT FOR LIGHT but for radio waves. His maths for radio waves (electro-magnetic ) gave this 186,000 miles per second speed. And then as far as I know , he only then said " Eureka ... Light must be an electro magnetic wave like radio waves as light had already been established as traveling at 186,000 miles per second ( or the meter equivalent ) " Only then " after his eureka" could it be described as maxwells electro magnetic theory of light .

 

Or at least that is how I understand it !

 

Mike

Edited May 7, 2014 by Mike Smith Cosmos

[copernicus1234]

Mike smith............The spark gap is not a induction effect since electrons are released when the spark is produced. The radiio indiuction effect cannot be used to justigy Maxwell since induction is not optical.

Edited May 7, 2014 by copernicus1234

[Mike Smith Cosmos]

Mike smith............The spark gap is not a induction effect since electrons are released when the spark is produced. The radiio indiuction effect cannot be used to justigy Maxwell since induction is not optical.

Now it is established :- electromagnetic waves start down at Very long waves and extend all the way up in frequency and shorter in wavelength all the way up through and including light waves from infra red to ultraviolet , and on up into Gamma rays at very short wave, very high frequency.

 

The photon is a description of any one of these frequencies related to the minimum energy of Planck's constant [ as you correct to say it was plank who identified this number as a discrete value during his radiation experiments from an oven] . It was Einstein who identified quite what was going on , in his experiments with the photo electric effect of emissions from surfaces. to establish the PHOTON. True this was with light. But Maxwells laws on Electro Magnetic waves and connection with light was already established. Einstein got the fame with his Special theory of Relativity with the Photon as being a Quantum value of energy or Photon of Electro-Magnetic Wave Packet. [ a descrete value as an integer value of Plancks constant ] / So all these men contributed to the Theory Ampere, Faraday Maxwell, Hirtz, Plank Einstein etc }

 

mike

 

That is probably as clear as 'mud' , but I hope it helps.

Edited May 7, 2014 by Mike Smith Cosmos

[swansont]

 

copernicus1234.................Quantum mechanics is based on Planck's blackbody derivation that is justifying Maxwell's electromagnetic theory of light. Most of Modern physicst is based on Maxwell's theory. In addition, the derivations of the EM wave equations of light, using Maxwell's equations is patently incorrect, unless you believe in scalar electromagnetic field theory. The Polish Susage.

 

You asked about the photoelectric effect, which is decidedly quantum.

 

What exactly is wrong with the wave equation of light?

Mike smith............The spark gap is not a induction effect since electrons are released when the spark is produced. The radiio indiuction effect cannot be used to justigy Maxwell since induction is not optical.

 

For electromagnetic radiation in free space, there is mutual induction of the E and B fields. Induction in optical materials runs into the problem of how quickly current can respond, and the fact that for an EM wave the electric and magnetic field amplitudes differ by a factor of c: you naturally see electric field effects dominate, e.g. in an antenna. But even an antenna doesn't respond classically in the optical regime. You can't generally wiggle electrons that fast.

[studiot]

A few corrections are in order here.

 

@Mike SmithCosmos

 

The corpuscular theory of light was propounded by Isaac Newton in 1660, who coined the term corpuscular.

His 'corpuscles' were able to explain reflection and refraction

 

Huygens was a contemporary of Newton who first proposed a wave theory, in 1680.

 

Although it was known that Snell's law could distinguish between the proposals by measuring the speed of light in dense media such as water, methods were not then available to make the measurement.

 

Foucault achieved this in 1850 and showed that, for speed at any rate, Huygens was correct.

 

Thomas Young developed interference experiments (1800) and theory that demonstrated behaviour only available through wave motion.

 

Following the subsequent discovery of phenomena (photelectric effect: Hallwechs 1888, Lenard 1902) only availble to corpuscular motion Einstein revived the corpuscular theory by naming the corpuscle a photon in 1905.

 

@compernicus1234

 

 

Maxwell, James. Dynamical Theory of the Electromagnetic Field. Royal Society Transactions. Vol. CLV. 1864.

 

 

 

I have 1865 in my reference.

 

James Clerk Maxwell, A Dynamical Theory of the Electromagnetic Field, Phil. Trans.Roy.Soc. London, 155:459 (1865)

 

Here is an extract from the introduction

 

 

The general equations are next applied to the case of a magnetic disturbance propagated through a nonconducting field, and it is shown that the only disturbances that can be so propagated are those which are transverse to the direction of propagation, and that the velocity of propagation is the velocity v, found from experiments such as those of Weber, which expresses the number of elctrostaic units of electricity which are contained in one electromagnetic unit.

This velocity is so nearly that of light, that it seems we have strong reason to conclude that light itself (including radiant heat, and other radiations if any) is an electromagnetic disturbance in the form of waves propagated through the elctromagnetic field according to the electromagnetic laws. If so, the agreement between the elasticity of the medium as calculated from the rapid alternations of luminous vibrations, and as found by the slow process of electrical experiments, shows how perfect end regular the elastic properties of the medium must be when not encumbered in any matter denser than air.

If the same character of the elasticity is retained in dense transparent bodies it appears that the square of index of refraction is equal to the product of the specific dielectric capacity and the specific magnetic cpacity. Conducting media are shown to absorb such radiations rapidly, and therfore to be generally opaque.

 

The conception of the propagation of transverse magnetic disturbances to the exclusion of normal ones is distinctly set out by Professor Faraday in his "Thoughts on Ray Vibrations". The electromagnetic theory of light, as proposed by him, is the same in substance as that which I have begun to develop in this paper, except that in 1846 there were no data to calculate the velocity of propagation.

 

You seem to be concerned with Faraday's and Ampere's experiments.

 

You see from the extract above that Maxwell was happy to acknowledge the work of others, but his introduction of an equation to describe an induced magnetic field (induction) was a theoretical extension of Ampere's law, by the introduction of what Maxwell called "displacement current".

 

Ampere

 

[math]\oint {B.dl = \left( {\mu \int {J.ds} } \right)} [/math]

Maxwell

 

[math]\oint {B.dl = \left( {\mu \varepsilon \int {\frac{{dE}}{{dt}}.ds + \mu } \int {J.ds} } \right)} [/math]

 

The additional term in the Maxwell equation gives the magnetic field induced by a changing electric field

 

You should note that his was a field theory. Faraday's law of inductiuon is a current theory, as is Ampere's Law.

Edited May 7, 2014 by studiot

[imatfaal]

You seem to be getting hung up on induction - there is far more than induction going into Maxwell's equations and even more comes out.

 

Gauss' Law describes the electric field caused by a static electric charge - it relates the Electrical flux to either the charge or the Electric field depending on the formation

 

Gauss' Law of Magnetism basically rules out magnetic monopoles by stating that the magnetic flux through an infinitesimal area is zero

 

Faradays Law determines that an electric field changing over time will induce a moving magnetic field or vice versa that a moving electric field will induce a magnetic filed changing over time

 

Ampere's Law - as modified by Maxwell relates a steady current in a loop with the magnetic field it generates - again or vice versa.

 

If you take these equations - set both the current and the charge to zero (ie open space) and take the curl you can with a little algebra end up with two second order differential linear equations. These are the wave equations. These only balance when the speed of the wave is equal to one over the square root of the vacuum permittivity times the vacuum permeability. These are independently measureable quantities. When you do the sums you find that the speed of the wave described by the two interdependent wave equations is the same as the speed of light.

 

 

xposted with Studiot

[copernicus1234]

Mike Smith.........Planck's blackbody is used to structurally unify induction with light since the blackbody radiation emits the radio induction effect and light but the blackbody light emissions is not an induction effect since electrons are released from the blackbody surface when light is emitted. Also, Planck's blackbody derivation is based on the blackbody body surface electrons oscillating at the frequency of light which requires an extra shot of Geritol or an extra large Polish hotdog with pickles and mayo.

 

 

imatfal........The derivation of the EM wave equations of light using the gradient method produces a horizontal wave. Maybe you should ask your JR. high teacher what a horizonatal wave is and what a transverse wave is.

Edited May 7, 2014 by copernicus1234

[studiot]

I'll just leave this little tantrum for the mods to sort out

 

go well

[copernicus1234]

Weeding out the weak.

[Mike Smith Cosmos]

copernicus1234

 

May be some useful links BBC documentaries on the hsitory of electricity

First part: https://www.youtube....h?v=3bQYsJP2R3Y
Second part: https://www.youtube....h?v=dPV6vPgjaFs

Third part: https://www.youtube....h?v=oPnS2WO2_0k:-

 

mike

 

 

 

.

Edited May 8, 2014 by Mike Smith Cosmos

[studiot]

+1

Cool links, Mike

Edited May 8, 2014 by studiot

[CaptainPanic]

!

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copernicus1234,

 

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[copernicus1234]

Maxwell's electromagnetic theory of light is based on Faraday induction experiment that is not optical. Planck uses the blackbody radiation effect that emits the radio induction effect and light to structurally unify induction with light but the blackbody light emission is not an induction effect since electrons are released from the blackbody surface when light is emitted. Lenard's photoelectric effect proves light is composed of particles which contradicts the lateral continuity of Maxwell's EM induction field. In addition, the wave effects and velocity of the radio induction effect does not justify Maxwell's theory since induction is not optical. Furthermore, the derivation of Maxwell's EM wave equations of light using the expansion and divergent methods are patently incorrect*.

*In the gradient (horizontal) method, http://en.wikipedia.org/wiki/Electromagnetic_wave_equation , a vector identity, that produces a second order gradient, results in the derivation of the EM horizontal wave equations of light that contradicts Maxwell's transverse wave structure of light that is used to represent polarization.


In the expansion method (Jenkins, Francis and White, Harvy. Fundamentals of Optics. 3rd ed. McGraw-Hill. 1957. p. 410), an EM transverse wave equations of light are derived. After Maxwell's equations are expanded, 16 of the first order differential components are eliminated to produce,


dEy/dx = - (1/c)(dBz/dt] ........... - dBy/dx = (1/c)(dEz/dt)..............Equ 1a,b


that are used to derive


(d"E/d"x) = c(d"E/d"t).......................................................................Equ 2


Equation 2 is used in the derivation of the x-direction EM transverse wave equations of light.


Ex = Eo cos(kx - wt)j..............Bz = Bo cos(kx -wt)k...........................Equ 3a,b


Using the electromagnetic transverse wave equations, in equations 1a forms,


d/dx (Eo cos(kx - wt)j) = - (1/c) d/dt(Bo cos(kx - wt)k).......................Equ 4


Using Bo = Eo, in equation 4 forms,


j = k (unit vectors). ........................................................................Equ 5


Equation 1b also produces equation 5 which I calls the unit vector of catastrophe. In addition, Condon also uses the expansion method to derive the EM transverse wave equations of light, using equation 2, but neglects the representation of equations 1a,b (Condon, Handbook of Physics. McGraw-Hill. 1958. 4-108). Furthermore, Hecht also uses the expansion method to derive the EM transverse wave equations of light, using equation 2, and neglects the representation of equations 1a,b (Hecht, Eugene. Optics. Addison-Wesley. 4th ed. p. 44). In general, physicists uses Condon-Hecht expansion method or the divergence method but physicists are intensionally concealing an extremely important and critcal fact, unit vector catastrophe, formed by equation 1a,b because the wave theory of light is the foundation of modern theoretical physics which is the reasoning for the intense group afford at concealment of the derivation of the derivation of the EM transverse wave equations of light. One of the agruements used is that Maxwell's equations are not vector equations and that equations 3a,b are not EM vector transverse waves.

[studiot]

 

(d"E/d"x) = c(d"E/d"t).......................................................................Equ 2

 

 

 

Shouldn't that be

 

[math]\frac{{{\partial ^2}E}}{{\partial {x^2}}} = \frac{1}{{{c^2}}}\frac{{{\partial ^2}E}}{{\partial {t^2}}}[/math]

 

 

I do not quite understand the point you are trying to make, but are you trying to suggest that your sequence of maths leads to the paradox that the j unit vector is the same as the k unit vector (equation 5)?

 

You cannot perform a one dimensional analysis. EM waves require three dimensions because the E part is orthognal to the B part and both are orthogonal to the direction of propagation.

 

Would you like me to work through the derivation with you and explain each step?

Edited May 9, 2014 by studiot

[swansont]

Maxwell's electromagnetic theory of light is based on Faraday induction experiment that is not optical.

You keep repeating this as if it's meaningful. It's not.

[copernicus1234]

The planets revolving around the sun was not meaningful to those who disagreed with Copernicus.

[John Cuthber]

The planets revolving around the sun was not meaningful to those who disagreed with Copernicus.

Perhaps, but the planets still went round the sun.

Speaking of things going round things, you can use a current flowing in a circle to generate light directly

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

and that does tie light directly to induction.

Edited July 10, 2014 by John Cuthber