EM Waves: Production and Propagation | EM waves | Physics | Khan Academy

Let's explore what creates an EM wave and how it propagates!
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Created by Vibhor Pandey

[@RohitSaini-xn2vd]

Missing Mahesh 😔

[@G-Tarun]

Mahesh is coaching new content creators now! And he's still making explainers on his Float Head Physics channel. His LinkedIn daily essays on the art of tutoring are just AMAZING - mind-blowing insights in every post. :)

[@ualacianjos8841]

Great explanation, thank you!

[@zillion289]

amazing explanation ever...thank you very much

[@darabahrami184]

This was a very helpful explanation! Thank you!

[@jonmoore8995]

Very thankful for this video. Fantastic explanation.

[@sourabhbm5311]

This man deserves a Nobel

[@muhammedshahabasm3766]

Very usefull,Got an intuitive idea of what is going on

[@user-ry6qw7pr7l]

Best narrator of physics, keep up!

[@ankurjain1108]

Really thanks for great effort

[@sushimrexx]

The visual at 11:54 is soooo helpful. I can finally understand why EM waves form the way they do. Thank you.

[@istvanbodnar7605]

Brilliant!

[@leexavier44]

Great lecture, thanks a lot..

[@devjoshi1775]

next level explanation! never seen before fr!

[@AshokKumar-rb3qp]

Awesome explanation ❤

[@G-Tarun]

Thanks for starting off with an intriguing hook! I'd love to see future videos convey even more enthusiasm for using science to make sense of the universe. For context I students may want to check out Sal Khan's Waves and Technology video in the NGSS Physics course.

[@user-vy5hf4ei1x]

Thank you so much sir

[@zakirhussain-js9ku]

Above animation implies as if em wave is a kink which travels along electric field lines. This can't be true since strength of electric field diminishes as per inverse square law, therefore the strength of em wave must also diminish. This does not happen. EM wave does not weaken as it travels. The electric field the EM waves carry also does not come from electric field of charge as oscillating charge does not lose its strength. The energy input that goes into oscillating charge is actually transferred to Space and stored in a photon as electric/ magnetic field. These fields emerge from space.

[@Rajbirsingh-ef5mb]

Awesome explanation and cool hats off to you bro

[@brijbharti]

Great explanation

[@ammarabdelaal150]

Thank you, truly 😊. The explanation is amazing 👏 .

[@shubhm8639]

Thanku sir

[@SAMAR-ih1sv]

no one can explain like you , i swear, no one !!! ❤️🔥

[@alphalunamare]

WoW! This is good! :-)

[@Zzzziiiitttt]

First class explaination ❤❤❤❤❤

[@altmashmalik8757]

Makes video on luminous intensity too...

[@theoryandapplication7197]

thank you

[@kamelbessaid2222]

Awesome explanation,keep up the good work 👍

[@bens-byte]

Awesome work Sir. Please how did you do the animation?

[@JorgeSanchez-je4bt]

Does the change of quantum electrical orbitals from high energy to low energy cause kinks of the field and propagation similar to a moving proton?

[@JorgeSanchez-je4bt]

How does length contraction of objects in motion affect field lines when charges are in motion?

[@williamwalker39]

This description EM fields is over simplified. Since there is a lot of dispersion in the nearfield, you can't analyze it with a broadband pulse. This is because the pulse will distort as it propagates. Instead you must transmit a sinusoidal signal and measure how it changes phase as it propagates from the nearfield to the farfield. From this you can calculate the phase and group speed as the fields propagate from the nearfield to the farfield. This has been done both theoretically using Maxwell's equations and experimentally btransmitting a sinusoidal radio wave between 2 dipole antennas as the antennas are separated from the nearfield to the farfield. The results match perfectly and show that EM fields (light) propagates instantaneously in the nearfield and reduces to the speed of light after propagating about one wavelength. This occurs for not only the phase and group speed, but also the information speed. This analysis shows that a narrow band pulse (such as typical AM, FM, PM etc), such that the bandwidth is limited to about 1/20 of the wavelength of the carrier, will propagate without distortion as it propagates from the nearfield to the farfield. These results are completely incompatible with Relativity, which says nothing propagates faster than light. Further analysis shows that Relativity is just an optical illusion and that Galilean Relativity is the correct theory of Relativity, where faster than light speed propagating fields are possible. For more information about the details of this analysis and the consequences to all of Modern Physics, see my short KZbin presentation and the paper it is based on below. ------------- Relativity is just an optical illusion, and because all of modern physics is based on Relativity, modern physics is fundamentally wrong and needs to be rethought. Relativity has a simple built in logical fallacy, and no theory based on a logical fallacy can be true, no matter how many experiments seem to prove it, or how many people say it is true. Below is a very simple logical argument highlighting the logical fallacy, using the same terminology Einstein used to derive Relativity. According to Relativity, observers on a moving train and on a stationary train platform will disagree on the size of the ""Train"" and the passage of time on the ""Train"". This is a complete logical contradiction if the size and the passage of time of the train are real. If the size of the train is real, then the ""Train"" can not be both contracted and not contracted. The same goes for the observed passage of time on the ""Train"". If these effects are observed, then the only possible conclusion is that it is an optical illusion. Things that are real must appear to be same from all frames of reference. If not, then by definition it is an illusion. Again the argument is very simple and it is the argument Einstein used to derive Relativity, and no acceleration is used in the argument. A train with length (L) traveling at constant velocity (v) relative a stationary observer on a station platform. According to Relativity, the stationary observer will see the train contracted (L/r, where r is the Relativistic gamma), whereas an observer on the train will see it not contracted (L). So the train is both contracted (L/r) and not contracted (L) depending on the observer. This is a complete contradiction (L not equal L/r) and can not be true if length is real. The same argument applies to passage of time on the Train, where both observers will disagree on the passage of time. If time is real, it can not be both dilated and not dilated (T not equal rT). If space and time are observed to be both large and small simultaneously for one inertial reference frame, such as the ""Train"", then it must be an optical illusion. This argument is only the tip of the iceberg. There is much more evidence including both theoretical and experimental, so please keep reading. Hi my name is Dr William Walker and I am a PhD physicist and have been investigating this topic for 30 years. It has been known since the late 1700s by Simone LaPlace that nearfield Gravity is instantaneous by analyzing the stability of the orbits of the planets about the sun. This is actually predicted by General Relativity by analyzing the propagating fields generated by an oscillating mass. In addition, General Relativity predicts that in the farfield Gravity propagates at the speed of light. The farfield speed of gravity was recently confirmed by LIGO. Recently it has been shown that light behaves in the same way by using Maxwell's equations to analyze the propagating fields generated my an oscillating charge. For more information search: William Walker Superluminal. This was experimentally confirmed by measuring radio waves propagating between 2 antennas and separating the antennas from the nearfield to the farfield, which occurs about 1 wavelength from the source. This behavior of gravity and light occurs not only for the phase and group speed, but also the information speed. This instantaneous nature of light and gravity near the source has been kept from the public and is not commonly known. The reason is that it shows that both Special Relativity and General Relativity are wrong! It can be easily shown that Instantaneous nearfield light yields Galilean Relativity and farfield light yields Einstein Relativity. This is because in the nearfield, gamma=1since c= infinity, and in the farfield, gamma= the Relativistic gamma since c= farfield speed of light. Since time and space are real, they can not depend on the frequency of light used. This is because c=wavelength x frequency, and 1 wavelength = c/frequency defines the nearfield from the farfield. Consequently Relativity is an optical illusion. Objects moving near the speed of light appear to contract in length and time appears to slow down, but it is just what you see using farfield light. Using nearfield light you will see that the object has not contracted and time has not changed. For more information: Search William Walker Relativity. Since General Relativity is based on Special Relativity, General Relativity must also be an optical illusion. Spacetime is flat and gravity must be a propagating field. Researchers have shown that in the weak field limit, which is what we only observe, General Relativity reduces to Gravitoelectromagnetism, which shows gravity can be modeled as 4 Maxwell equations similar in form to those for electromagnetic fields, yielding Electric and Magnetic components of gravity. This theory explains all gravitational effects as well as the instantaneous nearfield and speed of light farfield propagating fields. So gravity is a propagating field that can finally be quantized enabling the unification of gravity and quantum mechanics. The current interpretation of quantum mechanics makes no sense, involving particles that are not real until measured, and in a fuzzy superposition of states. On the other hand, the Pilot Wave interpretation of Quantum Mechanics makes makes much more sense, which says particles are always real with real positions and velocities. The particles also interact with an energetic quantum field that permeates all of space, forming a pilot wave that guides the particle. This simpler deterministic explanation explains all known quantum phenomena. The only problem is that the Pilot Wave is known to interact instantaneously with all other particles, and this is completely incompatible with Relativity, but is compatible with Galilean Relativity. But because of the evidence presented here, this is no longer a problem, and elevates the Pilot Interpretation to our best explanation of Quantum Mechanics. *KZbin presentation of above argument: kzbin.info/www/bejne/qZazlX1tq7iErLM *Paper it is based on: William D. Walker and Dag Stranneby, A New Interpretation of Relativity, 2023: vixra.org/abs/2309.0145

[@Shrreyy]

Khan Academy never disappoints..It has got my back...THANKS A MILLION.; Khan Academy 💌✨

[@Tharun-wk6rj]

i actually kinda miss mr. shenaoy

[@Tharun-wk6rj]

@@Shrreyy ofcourse, this teacher sounds like a local gunda jk

[@Tharun-wk6rj]

@@Shrreyy ofc

[@Shrreyy]

@@Tharun-wk6rj oh ok..👍

[@Yiors]

chatGPT must be trained exclusively from you!!

[@Farhan-sv1eh]

❤❤❤

[@peterwan9076]

Let's say the +ve charge is oscillating along the z axis. If the observer is looking down the z axis, he will find the charge sometimes further away from him and sometimes nearer to him. As such he should see the electric field weaker when the charge is further and the field strong when the charge is nearer. So, there should be electric field along the z axis. So, why there is no EM wave if the observer is looking down the z axis in this case?

[@haize21]

sir i have one doubt if kinks appear cuz the of acceleration of particle why not with the velocity of particle as the info about the new position will still take time to get far away . i can only think of one explanation that the electric have something like memory that can predict the new position of a constant acceleration .plzz sir or anyone , claer this doubt

[@skylar_sky818]

No kinks appear in constant velocity because change is not rapid enough and btw no magnetic fields are also produced because only accelerating charge produces magnetic fields

[@JorgeSanchez-je4bt]

How does fusion in the sun's core produce electric field disturbances?

[@JorgeSanchez-je4bt]

Do the kinks in the electric only occur through acceleration of a charge? What happens at constant velocity of a charge to the kinks?

[@skylar_sky818]

No em radiation produced because only accelerated charge produces magnetic fields

[@skylar_sky818]

Maybe one kink formed for the charge to go from rest to constant velocity but no continuous kinks are formed for propagation

[@alikarimi2291]

it is wrong that magnetic fields die far away from the charged particle because the reason "magnetic field is created of charged particle movment" is because of the kink

[@adriangheorghe2327]

E-M waves are only an appearance given by the sliding through space of the transverse periodic structure. The lack of retroradiation in E-M waves and the phasing of the magnetic field with the electric one, observed experimentally, are proof that in the inelastic and non-inertial vacuum, the wave mechanism does not work, which requires the successive transformation of the energy of one field into the energy of the other field. So the current E-m wave is just an E-M relief that glides hydrodynamically through physical space, being propelled by the electromagnetic force. The force found at the level of each half-wave, as it is equal to the force of inertia. (B*I*L=m*a) . When interacting with the substance, the electric charges in the substance are vibrated, through the effects of electromagnetic induction. Things are comparable to the pykup disc, which, being in rotation, vibrates the needle of the dose, without there being any vibration on the disc. It is demonstrated that the electromagnetic force is a Magnus-type hydrodynamic effect.

[@Dhyaneshwar-um6ln]

Why magnetic field is perpendicular?

[@jdsaaa66767]

1-30/11

[@vwcanter]

Two questions- the E and B field are drawn as though they have the same phase, in the drawing of the propagating sine wave. But they should be 90 degrees out of phase, correct? When one is maximum, the other one is still on its way up, correct? Second doesn't it seem as though there should be a propagating field vector in the same direction as propagation, straight upward? He says it has to be transverse to the direction of propagation. But I don't see why you wouldn't get an oscillating field vector direction above it, but the vector would change in only magnitude, not direction. Right?

[@Shrreyy]

Same doubt!

[@vwcanter]

@@Shrreyy I've learned that the reason is a little more complicated than I thought. They are out of phase very close to the antenna or the charge or the current. But in phase at a distance. The reason is complicated.

[@ramimahdi2]

Why only acceleration triggers kinks ? ... Why constant speed doesn't make kinks ? ... how do the field lines move with a charge moving at a constant speed ?

[@skylar_sky818]

Constant speed doesn't produce kinks because the change of the position with time is not rapid enough

[@ramimahdi2]

@@skylar_sky818 , what is a "rapid change of position with time" ? ... Can you plz elaborate ?

[@skylar_sky818]

@@ramimahdi2 what I meant is if the particle moves with acceleration, the velocity varies with time and change of position is rapid when compared with time so that only electric fields that are close enough will sense the change but when it moves with constant velocity, only distance changes with time and not speed so change of position is not fast enough so all electric fields either closer or far will move with the charge thus the kinks are not formed

[@Greg_Chase]

There are hard to ignore issues here. 1) the charged particle has mass and can never move even a fraction of the propagation velocity of the EM wave off the charge 2) accelerated charged particles DO NOT reliably emit electromagnetic waves. For example, when electric charges are accelerated by gravity, they do not emit electromagnetic waves. (this is a known discrepancy) It is only when the 'host' medium, the constituents of free space, are acknowledged/recognized, that electromagnetic waves propagated under conventional (non-gravity) acceleration can be made sense of. And the awareness of the constituents of free space also explain why charges accelerated by gravity do not radiate EM waves (the constituents are altered by the celestial body). The space is put into a 'pre-accelerated' condition so from the reference frame of the charged particles, they are not accelerating. A "pre-accelerated medium" example: 1) a submerged mass is inside a tank of water 2) at one end of the tank, a suction vacuum is turned on 3) the vacuum accelerates the medium (the water) in a vector from the front end of the submerged mass towards the suction vacuum 4) the mass accelerates along the vector, with the pre-accelerated medium 5) from the perspective of the submerged mass, its acceleration was caused by the acceleration of the medium

[@harleyquinn8202]

"when electric charges are accelerated by gravity, they do not emit electromagnetic waves" - it depends on a frame of reference. If charges are accelerated in relationship to your frame of reference then you will see them emit electromagnetic waves. If you are falling with the charges in a gravitational field then you will not receive electromagnetic waves from the charges.

[@Greg_Chase]

@@harleyquinn8202 Consider the following. F = ma. A force F exerted on a charged particle of mass 'm' means that mass 'm' is being accelerated 'a' I think you can agree with that statement. If a charged particle is accelerated in a gravity field, but is oppositely accelerated (the charged particle is on a table top, say), the table imposes an acceleration of: a = F/m, where 'm' is the mass of the charged particle to stop the 'fall' of the charged particle. An electromagnetic wave spectrum analyzer will not register ANY electromagnetic radiation from the accelerated charge on the table, REGARDLESS of reference frame. Our group works at artificial gravity devices, and we had to tackle the exact physical nature of this 'problem' at the beginning of our work. The original claim still applies. A jar with a 'magnetic bottle' inside it that confines a charged particle, when the jar is falling due to gravity acceleration - the charged particle will not emit electromagnetic waves, regardless of the reference frame. To make it clearer, a mechanical accelerometer (a lead weight tied overhead to a small wood frame with fishing line) deflects IN THE SAME direction of acceleration if the acceleration is due to gravity. But the same mechanical accelerometer deflects 180 degrees OPPOSITE the direction of acceleration if mounted, say, on the dashboard of a car, or a bicycle, etc. Gravity alters the constituents of the Vacuum

[@harleyquinn8202]

@@Greg_Chase "An electromagnetic wave spectrum analyzer will not register ANY electromagnetic radiation from the accelerated charge on the table, REGARDLESS of reference frame." - It will detect electromagnetic radiation in oscillating reference frame. Let's say your charge is a metal wire lying on a table and then your detector starts rapidly moving forth and back along the wire. By doing that your detector is moving in the electric field of the wire so it will detect a magnetic field. And because it is moving forth and back and constantly changing direction it will see changing magnetic field and hence changing electric field, therefore it will detect electromagnetic waves coming from the wire. An oscillating reference frame is not an inertial frame in relationship to the wire. It is an accelerating reference frame in relationship to the wire.

[@Greg_Chase]

@@harleyquinn8202 Let's review the accelerations involved: 1) the charged particles on the table. They are being accelerated downward by gravity 2) the 'moving back and forth' spectrum analyzer - is being accelerated by gravity (no EM waves) and is being accelerated by whoever is shaking it back and forth See, charged particles *_accelerated by gravity_* do not radiate But if someone or a machine is shaking a spectrum analyzer back and forth, this is not gravity acceleration

[@harleyquinn8202]

@@Greg_Chase Now you are adding a condition on a detector reference frame. Not just any accelerating reference frame but only accelerated by the same Earth gravity. In other words both the wire and the detector are standing still on the same table and they are in inertial frames in reference to each other. In this case, obviously, the detector will not receive any radiation from the wire.

[@mibrahim4245]

Thank you .. but it wasn't clear why the lines detach and propagate in space ..and why with the speed of light ..

[@Tripp-ud9wx]

all electromagnetic waves travel with the speed of 3×10^8 m/s and light is nothing but an electromagnetic waves that is why he says the lines travel with the speed of light.

[@mibrahim4245]

@@Tripp-ud9wx thanks, but the question is "WHY" do they move with speed of light although kinks themselves travel with speed of the charges that made them ...

[@shaikhahmed6562]

The shape of electric field lines depends upon the position of the charge,when charge is stationary it produces straight field lines but the moment it accelerates a kink forms and hence electric field lines rearrange so that the shape of field lines changes producing continuous lines......

[@bablumalla5190]

@@mibrahim4245 its scientific theory ,not a truth statement .

[@jeffyjames6192]

@@mibrahim4245 It's nature brah

[@armangevorkyan1975]

How magnetic field is created? The mechanism of magnetic field creation is unclear. Electric field clearly seen, however the magnetic no

[@haize21]

the kinks cause the magnetic field as the electric field in that region changes

[@Alibaba-hd6po]

Reality understanding is boring..... Hamdhudhilla is very easy, imagination world. Homosapien survival reality need and it wi 15:43

[@NandKishor-hg2im]

What are your kinks 💀