Electromagnetic waves and the electromagnetic spectrum | Physics | Khan Academy

Created by David SantoPietro.
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[@pinkribbon1007]

you explained this concept better in a 12min video than my 2 hour of lessons from my own teacher, thanks

[@Cooper_mostyn360]

Ong

[@vsvicente]

Khan Academy is incredible. It is astonishing. It is without words. Thanks.

[@thegeth4293]

so, are our eyes just antennas that are tuned to visible light frequencies?

[@halconsalvaje]

more likely, the entire human body is a receiver

[@josepadilla-dv3ld]

no, there are molecules in each cell which react to different frequencies

[@DLewis-pn8yo]

Pretty sure the cones are shaped like antennae

[@harikrishnav.s.1299]

More of a photochemical receiver than an electromagnetic reciever

[@nanzhang5777]

Well, in some ways I would say “yes” but also “no”. Do you know what I mean?

[@NavajoLion]

You are the best physics tutor on Khan!! I was so relieved to hear you teaching once I turned on the video!

[@Menzel_h]

best video ... finally i got the electromagnetic waves :D

[@zain6933]

hows 11th grade?

[@barnabaskatona4279]

Came here for answers to my hw, but even after knowing them i stay cuz its so well explained and interesting. Well done

[@chemgeek1682]

In the example of the electromagnetic wave with perpendicular E and B fields, you say the wave propagates to the right. Based on the way you drew it, that's not actually the case. E cross B gives the direction of velocity and so in your example the wave propagates to the left (negative x direction).

[@shettyrohit75]

yes.. correct

[@AbdelJimenez]

Instead of criticizing and correcting which is easy and anyone can do, why don’t you make a better video? This young man has made an effort to explain electromagnetic waves and help improve everyone else. Try to do the same instead of finding fault please. It’s much harder to create things, but it will make you proud of yourself in the end. I’m sure you can do it.

[@jashuah9993]

@@AbdelJimenez he just showed the mistake and I am very thankful

[@poiuwnwang7109]

Chemgeek16 is right. but Abdel Jimenez, he just shows a mistake in the video, he is NOT criticizing.

[@josephboog]

Yes I agree as well. The E and B fields are backwards. The right hand rule states if you start your right hands fingers in the E direction and CURL to the magnetic field, your thumb will naturally point in the direction of propagation. The YELLOW should be Electric Field. The RED should be Magnetic field. Great video though!

[@gruviboy]

Also where one field is changing at max rate (crossing zero) the orthogonal field should be at max amplitude...the picture is wrong. Electric and magnetic fields never cross at zero together, one field should be (phase) shifted by a quarter cycle in the drawing.

[@johnbell3621]

@@gruviboy Are you sure? All drawings show the 2 fields in phase as they propagate.

[@flavarz]

very informative! thanks for the share

[@jennylezlo2034]

this playlist has helped me through my A levels physics. how universal knowledge is!

[@shmuelmunitz9934]

Wow, finally got it! This video does a great job explaining this!

[@microk7648]

I know I'm commenting on a 9 yr old video but it's got to be said - thank you so much! I was looking for the resource that could reconcile my understanding of electromagnetism in wires and magnets and electromagnetism when speaking about light and radio waves. And here it was posted nearly a decade earlier, a little over 10 minutes long. You absolutely smashed it. Thanks again.

[@goku1863]

That Hulk Reference Doe.

[@dalsenov]

Great lesson! Very fundamental informations! Thank you!

[@alexandrabidoli8090]

Your video is genious Really helped me and have me a bigger interest in the electromagnetic spectrum

[@mauriciopaguada9875]

Salman amigo : intercambia la rotulacion de E y B en las graficas para que la direccion de la propagacion cumpla la regla de la mano derecha. Saludos desde Honduras y apreciamos este gran esfuerzo y proyecto de transmitir conocimientos a la humanidad!

[@rafiulhredoy2556]

Best ever ! Without any confusion and ambiguity.

[@nailakcura]

I think the wave direction should be the opposite direction, when using right-hand rule, the finger tips conserving from E to B, the thumb shows the wave direction, which is left

[@amazinc754]

i agree

[@lljudarll221]

This video has really helped me, thank you.

[@danielray5571]

I believe that X coordinate @3:55 should be a time coordinate if this graph is to show self-propagation. Using a distance coordinate creates a graph showing the two fields frozen in time, and therefore shows the oscillation of the producing charge instead.

[@barjosa31blogspot83]

THANKS MAN!!!

[@TheLunasticks]

THE LUNATIC FRIDGE IS NOW ALSO ON EDUCATIONAL VIDEOS. I HAVE TO STUDY TOO, Y'KNOW?

[@beetlesstrengthandpower1890]

Can a rapidly magnetic field create light? Would be interesting

[@tafadzwachuma2000]

Splendid. Easy to understand. Thank you

[@printheoswartz3043]

Wish I could like a thousand times...sooo effective👍

[@matthennagersguitarlessons]

Very helpful! Thank you!

[@McGavel1]

Very great explanation - thanks!

[@onisarb]

Nice video! Extremely pragmatic approach!

[@AM-gq4zi]

Gotta a test tomorrow hihihi thank you very much sir!

[@SubhashiJayasekara]

Thank you so much. You have explained it well...

[@MrBademy]

epic video !! great job :P please do more this is very well explained and interesting!

[@fitnessmadness3109]

Sir please arrange these lectures of e.m waves in your playlist Then it can help more

[@GodbornNoven]

easy to understand thanks

[@hassanjaved6485]

Thank you for explaining it.

[@apearson79]

This guy is my fav on all of Khan academy.

[@ptiwatthanont]

Clearly! I have never believed that the waves are in 2 dimensions. But OK, I will do from now on.

[@dineshdkkumar2215]

One of the best video I have ever seen. Thank you for this

[@TobyDK91]

Today AM is used more for UHF radiosignals and FM in the VHF area. Due to the fact that frequency modulation becomes tricky with higher frequencies. Opposite to what you said.

[@fmusicede7384]

Great video! Thanks

[@akashdeephazarika8138]

great explanation

[@kristeinsalmath1959]

MMM, to see if i understood. EM Wave is the way how energy tralves through vacuum. While increse the velocity of wave the length decrease. So WiFi wave wave transport energy(On/Off) when is up 1 or 0 is down?

[@byunbee3051]

Istg i'm gonna get my degree thanks to you.

[@ojgfhuebsrnvn2781]

I have some small question. Just a few videos back we learned that magnetic field is technically infinite and has to loop. However here we have boundaries like Amplitude. How do we interpret it? Is it also technically a loop and lines do extend infinitely but we just don't draw them because strength of a field diminishes rapidly or what?

[@kan-zee]

excellent layout demo's thank you. I hear a lot of chit chat about the 7.83 Schumaans Resonance Brain frequency (aka Earths pulse) and this 440hz is chaos frequency and the 528hz is the Miracle frequency...can you share a video on these subjects..really enjoy your style of teaching. Cheers

[@arianagrande1312]

Can someone give me some trivia about EM Waves? Pleaseee. I need it for tommorow 🙏

[@user-cx9th7hv3e]

This was really helpful thank you❤

[@ninadelectronics]

Nice Video

[@travelerUSA]

Great. Thx

[@knightthe4031]

very useful video!

[@arushjha4022]

I’m just 13 and I love all this! Damn!

[@realcirno1750]

im 9 lool

[@tinytots7122]

@Henry HUNG [07N15M] and here is my 3 yr old sis watchin this with me and asking me questions like what is electromagnetic??? and oh the way she is pronouncing it is way too funny

[@AmanKumar-ef7xz]

You have nailed it 👍

[@majorfrozen]

Thank you from Texas

[@Kukkane]

wawes what ever they are, have same principals. the type of the wave(s) that are crossing determines outcome. Bouncing on different surfaces is where the fun starts :)

[@hazleenazlee506]

You’re incredible

[@TheJavierDavalos]

man you are good

[@arthurvin2937]

Visible=visible to normal human eye. All ranges are visually visible. My brother can clearly see infrared in day light, had tested him many times by various types of IR remote controls even with dead batteries. EM waves travelling through the empty space without media is quantum physics.

[@basionyshehata]

Thanks!!

[@littlecat3324]

you are so good

[@OilDrillingChannel]

Awesome

[@larsl.christensen6560]

Electromagnetic waves is used for remote neural monitoring and mindcontrol these days through the application of RADAR

[@atriagotler]

This is like 100x more useful than my textbook. Thanks! (And I'm from Finland, which is considered "high standard" in education. Bullshit imo.)

[@AimzIIT]

Yours Grade ?

[@atriagotler]

@@AimzIIT upper secondary, ages 16-18 yr

[@mikhileshmhirphode4374]

THANK YOU

[@cosmicyoke]

They (the fields) do not create each other. They are both caused by charge density and current density.

[@amirael-komy6638]

"Gamma rays won't turn people into superheroes but it's very energetic" My disappointment is immeasurable and my day is ruined

[@tech-savant]

6:08 what determines that frequency, how do you get that magnetic field to oscillate quicker?

[@sccm100]

This is so much better when you're high

[@eujebenqo6159]

What is the'' ocean'' for electromagetic waves? what is their medium? they run on what? Black water?

[@eduardo0796]

Electromagnetic waves can propagate through a medium or through vacuum. They are not like mechanical waves, like sound or waves in the water, that do need a medium (ie, air and water respectively) to propagate.

[@dreddy5953]

This is one of the bst channels i have ever seen. This is the only channel made me better in my physics!!

[@schpoingle]

How are schisms of intelligence supposed to interact with each other?

[@lizethvargas6577]

Build a distribution of point loads along the That far from them their electric field along the axis varies by 1 / r6. Electromagnetic physics, please help me with this question, thank you

[@c9338]

Do these waves have something to do with their source voltages?

[@zayedali5675]

yes

[@AwesomeRocken]

Smash electromagnetic waves with sounds waves with a physical matter (metal) with accelerated electrons controlled waves length and power an open point like a hole will be allow a physical metal object to travel to any point in time

[@SamSarwat90]

can you imagine that i did read your post twice? Before realizing that u nigga are high

[@zarinkabli3524]

Radio waves of less energy passes through opaque substances then why not the visible light waves of higher energy pass through the same?

[@DLewis-pn8yo]

You forgot to include the lengths of other regions of EM spectrum

[@mk-ultraisnowwireless.6478]

How can i shield myself from "Voice to Skull" technology & remote neural weapons?

[@zippolighter0177]

that name tho

[@c9338]

Do all these wave lengths have constant voltages?(I mean constant peak voltages of the electro magnetic wave)

[@darionz]

Can the Mandelbrot set define electromagnetic waves?

[@grantofat6438]

Lol. "It didn't require a current, it just required a changing electric field." Those two are the same mate.

[@markuscwatson]

ExB should be in the direction of V.

[@NJames-dh6kz]

It's x-ray TECHNOLOGISTS, not "technicians". But, still, good info. Thanks.

[@jackiechiu20]

In EM wave, I see the same phase angle for E and B field. But why in electric circuit there is always phase angle between voltage and current.

[@werds1392]

Yu Chiu most likely the lack of a phase angle in the constituent waves of light is due to the fact that photons do not experience time since they move at the speed of light. In electric circuits, these phases happen as a result of how differential components like capacitors and inductors interact with electrons which have mass and cannot instantaneously equalize their positional energy while moving around in a circuit

[@jonathansmilestein9504]

Fnnn Eh. Great presentation.

[@jackgrimsinn]

could an aquifer work in any way with this?

[@Sniiigel]

Is there an EM field where the red and yellow line cross each other?

[@axy93]

EM wave as drawn is propagating in the wrong direction! Please fix!

[@cosmicWil]

+Andrew Yang That doesn't matter. Light can be polarized in any direction. Up down left and right are completely relative. As long as the fields are perpendicular there is nothing wrong with what he drew. For example if you rotated the light and shifted it back by one period it would look exactly like what you described or might see in a textbook.

[@philipchristian9935]

+Wilfredo1242 Well in general, if the wave is propagating in a normal medium, the direction of wave propagation is always in the E X H direction, which means the video has it wrong. We aren't dealing with metamaterials as this is just a basic intro to EM waves, and thus the video has it wrong.

[@erwinbauernschmitt4104]

But that's not really the point. The point is to explain the concept behind it. I didn't understand it at all but now I am beginning to make some sense of this.

[@sender1496]

Actually, the direction IS important. The wave would NOT travel to the right, but to the left. (E, B, k) should be positively oriented in a sense that E x B is in the k-direction (k being the wave vector). Andrew Yang is completely right, and you can't just rotate/shift to make it right...

[@lopamudrakar5680]

Actually, he used it only for representative purpose. He was not explaining the direction.

[@nervinekhaledshoukry740]

It's very confusing for 6th graders , but amazing .

[@christiansadykbayev3486]

@Nervine Khaled Im a 6th grader too!

[@w.scottwomer2416]

How does 90 degrees point into screen and point out of the screen?

[@moukafaslouka4796]

Why does the changing magnetic and/or electric field move outwards? I can understand that they interact, but you have completely failed in explaining how they move.

[@rproctor83]

+Mouka Faslouka Good question, I'm not entirely sure that I know what I am talking about here, but if I understand properly an EM wave is actually a disturbance in the EM field. It's this disturbance that we describe as a wave, and it propagates outwards forever or until it is absorbed. It moves because it has to move, it is intrinsic to it's natural phenomena and the laws of nature itself. Imagine the waves in the ocean, if there were no friction and this example took place in a vacuum, then when the waves of the ocean move they would move on forever as the forces emitted and absorbed would perfectly create perpetual motion. It is like this that an EM wave moves along the EM field. However, here on earth there is much noise and so em waves dissipate at a much higher rate. When an EM wave travels through some other medium it excites the atoms in whatever mass it was consumed by, vibrating the electrons to the same frequency it was consumed at and releasing a new em wave of it's own, which in turn moves to the next atom, and the cycle repeats.

[@harshith1999]

And also there are some more things which always baffles me about EM waves: 1. Does EM wave exist only in this point which he shows at 3:22 ? or in the entire space between that point and the end of the arrow? I mean can that field be experienced all along that field vector line or just that point? 2.Suppose I place a small magnet along the line vector of any one of the field, will it deflect? I mean in a point between the point at 3:22 and the end of the arrow I place a tiny magnet. 3.Consider only visible light. Suppose the amplitude of this field is tooooo much, will a tiny magnet kept 5mts away be deflected too if the amplitude extends 5mts ? I mean a light traveling parallely to me should be visible to me if it has higher enough amplitude to make it to me. 4. Will vibrating a permanant bar magnet also create a EM wave? If so, what about accelerating a magnet? Now I do know that the E and M field of an actual EM wave is so weak that there actually is no magnet other than proton n electron (I'm hoping) that can get deflected. But I am just talking about a virtual magnet here in order understand.

[@rkaur6166]

so does light have both a positive and negative charge? therefore allowing an electrical field?

[@sunahangrai3601]

it's okay that a positive charge or a unit positive charge creates an electric field but i don't get sense how can we get them how do you isolate a positive charge for your lecture purpose ??

[@VipinKumar-cx9np]

Sir EM waves ko achhe trika se batai

[@marlonsaveri]

Is all eletromagnetic wave originated by a charge or a field oscilating somewhere? And every charge oscilationg in the universe send energy (create photons) in a direction?

[@RyanJumarPantoja]

is it B in z axis right and E is in Y?

[@johnmoor8839]

but what are the waves made from if not particles?

[@herobrinemaster8399]

6:00 or so we all know the wavelength is 1.5 right

[@Duck-pv5ob]

I'm a little confused. If electric and magnetic fields are two sides of the same coin and represented as a kind of perpendicular wave, how come most light is represented as a single wave? Are the two combined to come up with a single wave?

[@SuperMrObserver]

AM and FM are types of modulation, not higher or lower frequencies ??!!

[@halconsalvaje]

so can you tell what is the maximum frequency we can use on cell phones? I know their use can disrupt our brain function, because it meses with neuron transmission

[@envious3409]

halconsalvaje They transmit radio waves and light... Light can't break through the skin, radio waves can but when radio waves are absorbed by your skin they can't escape, so infrared is produced and held in your cell or your head. Not really dangerous at all. You absorb more radiation whilst being with another human than having a phone against your head.

[@mendozaalfeoi.3086]

MEDICAL PHYSSICCCSSSS