Effect of Electromagnetic Radiation on Metals

[@MrNibiru2112]

Hi, prof.From Tanzani, I am enjoying your very clear descriotion on how nature works..I wish I had even half of your teaching in my hugh school...Thank you si much, and welcome to Tanzania.

[@td866]

The statement at 32:05 that it is the horizontal component of reflected light that passes through a vertically polarised lens is entirely out of line with what I was taught or what I could find written elsewhere. All the sources I find say that reflected light off the ground producing glare is mainly horizontally polarised and that a vertically polarised lens blocks this glare (i.e., horizontally polarised light). edit: did I misunderstand something??

[@DrPhysicsA]

You can have a magnetic field in a metal. That is, for example, what you get in a a bar magnet. If you have changing magnetic fields then the free electrons in the metal will flow in response to the changing magnetic field creating eddy currents. You can find out more about these in my video on transformers and the effect of eddy currents.

[@kpmaynard]

Thank you, professor, for your lucid, detailed explanation. You artfully leave no loose ends, every important phenomenon is identified and explained.

[@Cheeriot]

You have carried me through A levels and now my EE degree. Cheers!

[@DrPhysicsA]

Delighted to hear it. Congratulations on a splendid result. Have a great time at uni.

[@revgro]

Another excellent video. Thanks for including the explanation for how a polariser does and doesn't work.

[@DrPhysicsA]

Thanks to your kind comments. I think I have derived the four boundary conditions when the metal plate is perpendicular to the incoming wave. It becomes much more congregated if the metal is no longer perpendicular. You are right that the skin effect does break for gamma rays which are capable of penetrating metals e.g. lead. I shall cover that in my video on absorption of electromagnetic radiation

[@tokas79]

Professor, I am your fan now. Lucid presentation.

[@snes09]

This video was great! I just came to understand how polarizers worked for a part of a QM lecture I was stuck on (which you did in fact help), but I was surprised to learn much more than that. Thanks a bunch!

[@samuelpaulsen3971]

Videos are extremely helpful, even seven years later (Guess the math doesn't change much;)) Well done

[@DrPhysicsA]

As others have pointed out, the electric and magnetic fields of the electromagnetic radiation oscillate in a plane which is perpendicular to the direction of travel. The electric and magnetic fields themselves oscillate at right angles to one another but no part of those oscillations can be in the direction of travel of the wave.

[@MyWorld-sx2tq]

That was clear and amazing! THANK YOU VERY MUCH PROFESSOR!

[@DrPhysicsA]

The video which is due to go up this week on waveguides covers some of this material.

[@chadjad1]

Hi Dr Physics A, this comment isnt really relevant to this video. But I just wanted to say a huge thanks for posting these revision videos. I used them pretty much as my main revision material in my A level resits during my gap year this year, and I managed to improve my overall grade from a C to an A, meaning I was successful in my university application! thanks again!!

[@kazimazed9049]

What happens to the magnetic field in metal?

[@MusicByNumbersUK]

Great video! slowly absorbing most of it! :) Have you done a video yet that explains group and phase delay? I seem to have missed it if you have. thanks!

[@benjuliebenjulie7414]

If the surface elctron(s) creates a wave that cancels the incomming em field wouldn't it also create an oscillating field in other directions as well, including into the core of the metal?

[@tokas79]

Certainly. Electrons will create radiation or I should rather say EM filed in forward direction. But, again, other free free electron are present there (just inside) to produce cancellation effect of incident field. It depends on conductivity, permeability and some other parameters also. Eventually, in practical sense, radiation is stopped inside metal (within few nanometers for visible radiation).

[@rgudduu]

@@tokas79 , so if i hv one copper wire, then electrons are oscillating up n down, to try catch up with any incoming E field oscillating. So there shd be a current on the wire's surface, forever flowing up n down. Is that correct?

[@justpaulo]

Hi, thanks for this series on electromagnetic radiation. It's been great to follow and very instructive. One day mankind will thank you for all your lectures and knowledge you post out here. In the meanwhile I have a few questions: 1) what happens to Bt (4th equation) in the perpendicular metal plate example? 2) And what if the sheet of metal is not perpendicular to Z? What happens to En and Bt? Does the rope example still applies here? 3) Does the skin effect breaks for gamma rays?

[@drd9973]

Your videos blow my mind. I try to keep up. Can light move perpendicular to its angle of transmission? Maybe I didn't say that right. Does or can light travel in the same direction of the E field?

[@SamiCodhen]

Is it related to refraction and reflection at the surface of a good conductor?

[@burcmm]

Another great lecture! Would you consider discussing surface effects in conducting materials with reduced dimensions (such as submicron thin films and etc.) ? This would probably be graduate level but grads would certainly benefit from such a lecture.

[@natjimoEU]

THANK YOU SO MUCH, ty for pointing out this wrong way of thinking!! i have seen professors explaining this in the wrong way and finally i found the right answere!

[@andrewschiessl9941]

What if the piece of metal is technically grounded? Can electrons pile up on the surface of the metal and reflect the E field wave coming in? Or would the electrons be shunted to ground and not reflect an electromagnetic wave?

[@DrPhysicsA]

I am using the general principle that there is no E field inside a metal conductor.

[@yaswanthsaijetti531]

Excellent lecture. I just have one doubt, is there any expression for reflectance of metals?

[@vaishnav4035]

According to the magnitude of the tangential E field electric charges will move inside the metal.. On the surface.. Sir Is this how reception in an antenna work....? is Length of the antenna is a consequence of that?? Please..

[@motoservo]

Does light penetrate (or, "fall off") the entire skin depth? Or, some undiscussed partial of that distance?

[@samuelpaulsen3971]

You mean the ENTIRE 2x10(-6th)? ;) Haha, I'd be afraid of getting quantum

[@654321123able]

superb sir....really really nice..

[@DracoMhuuh]

Isn't E=0 a condition of electrostatics? If yes, how do you justify using that condition to calculate the boundary conditions etc? Is it because of the high speed at which the electrons move in a metal to compensate for the E field that is in the metal when an external field is applied?

[@dumass00072]

So if I had a transformer core (made out of whatever one desires) and of whatever shape one chooses. Is there any way EMR can have any effect on the core or the windings(be them shorted or not)?

[@meocats]

What free source models hydrostatic dampening (looking for a knowledge source on the physics of that)?

[@rgudduu]

excellent. Sadly i see this video and the comments are 5 years old. Are u still willing to answer, sir?

[@juliusvictorcabreros6641]

Hi. thank you for the video sir, can you help me with my problem. Problem: Is there any electromagnetic wave that can pass through or penetrates the 1 inch aluminum wall? If there so, can you show me how? Is there calculations I need to make to know what frequency range of electromagnetic wave that can penetrates 1 inch aluminum wall? I will be so much happy if you consider my questions. Thank you. :)

[@JosePerez-zw3dr]

x-ray, gamma and neutron

[@rgudduu]

If a metal perfectly reflects back emag wave, then why does a metal easily get heated in sunlight?

[@alexmanbeck]

a metal conducts so it heats up and conducts easily form the suns energy

[@rgudduu]

@@alexmanbeck , the video says, a metal 100% reflects back electromagnetic wave incident on it. And sunlight is an emag wave. Heat is energy. How does a metal, then, accepting energy from sunlight?

[@JosePerez-zw3dr]

This is a physical model, where it is considered a perfect metal. Real metals have defects so they absorb some of the radiation in different ways, which is why real metals get hot.

[@JosePerez-zw3dr]

Even in a material considered perfect, reflection is one of several effects that occur in the interaction of radiation with the material, which are probabilistic and depend on the frequency of radiation among other parameters. Like the photoelectric effect, the compton effect and the formation of pairs. These can cause the radiation not to be reflected, but to be dispersed and emitted in the thermal region of the electromagnetic spectrum

[@1toneboy]

Well the electrons cancel out any electric field in the metal, but there IS an electric field in the metal? Otherwise electricity wouldn't work because electron drift velocity is so slow.

[@marcisrancans]

Electron diffusion velocity is slow.

[@premiere3610]

Please switch on the auto generated subtitle

[@czesaww8232]

With all respect to maxwell's equations but in the first equation something is missing. Electric field is not just a function of electric charge. It is also a function of the energy of this charge. So the same charge can have more or less energy. It manifests itself at work which can do the same number of charges depending on the value of the electric field.

[@legendarylightyagamiimmanu1821]

Czesław Wiech it’s also a function of some radial distance r And you’re talking about electrical potential

[@czesaww8232]

@@legendarylightyagamiimmanu1821 because the electric potential, volts and electric field are one and the same.

[@ΟριζόντιοςΚατακόρυφος]

light always travel perpendicular to the direction of the E and B fields

[@DracoMhuuh]

Considering ofc that light is not an electrostatic phenomenon since changing E-field and changing B-fields

[@alext9067]

The word on the street is that a photon must be a particle if it can produce the photoelectric effect. I'm not buying it. From what I can hear you saying, you don't buy it either. Please elaborate if you would care to. Thank you and extremely excellent videos. I subscribed within the first 3 seconds.

[@MusicByNumbersUK]

Fantastic thanks! look forward to them! :)

[@ΟριζόντιοςΚατακόρυφος]

Excellent.Thanks!

[@akashraj5073]

Gr8 lecture

[@copeland694]

Do u think its possible the the wtc 1 and 2 were brought down in part by emr?

[@irinealap3843]

di ko magets lodi

[@Edwinthebreadwin]