Rayleigh Jeans Law & The Failure of Classical Physics

The Rayleigh-Jeans Law was a Classical attempt to explain the observations of Blackbody Radiation. It was based on the sound principles of Classical Electromagnetic Theory, and Thermodynamics.
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The Rayleigh-Jeans Law is a formula that describes the intensity of electromagnetic radiation emitted by a black body at a given temperature. The law was proposed by Lord Rayleigh and Sir James Jeans in the early 1900s based on classical physics principles. However, it fails to explain the observed behavior of black body radiation at higher frequencies, known as the ultraviolet catastrophe. This discrepancy marked a major failure of classical physics and played a pivotal role in the development of quantum mechanics. The solution to the ultraviolet catastrophe was eventually provided by Max Planck, who proposed that energy is emitted and absorbed in discrete units or quanta, laying the foundation for modern physics.
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[@FortheLoveofPhysics]

1. Blackbody Observations - kzbin.info/www/bejne/fIPHY2t5gduAh68 2. Rayleigh Jeans Law - kzbin.info/www/bejne/oXndZ62YedacnLM 3. Planck Energy Distribution - kzbin.info/www/bejne/qnK9in6EgNCrqZY 4. Summary - kzbin.info/www/bejne/gYObhKCQast6f8k

[@micomicomi5485]

Damn, yet another beautiful video. I know these videos may not have a lot of views, but please please keep making them. Literally the best teacher I've seen on KZbin (your handwriting and drawings are amazing as well)

[@user-sz5dt9ih7f]

Listen very carefully. If you want to learn the nuances of black body radiation that no other video or text explains in a historical and common sense manner, then watch this gentleman's videos and pay very close attention to his every word.

[@johndivine6865]

❤

[@vatsaltanna6010]

I agree. I saw many videos before I landed on this one. I thought that I was never going to understand the derivation of this equation. But thanks to this fine gentleman, I can now derive this equation. Really good work.

[@sanjayyashwantsohani4820]

Yes ,you are correct,very neat explanation .

[@noelomaolchraoibhe3911]

Agreed 100%. This is a magnificent exposition......absolutely masterful. Its clarity allows one to reflect on the outsize role the cavity geometry played in Rayleigh-Jeans strategy; it seems classical EM & thermodynamics "failed" because they essentially assumed the power into the box could drive an infinite number of overtones which doesn't feel quite realistic; Rayleigh's success modeling the analogous scenario (25 years earlier) of standing sound waves in a cubical room surely dominated his thinking here. That said, we must assume alternative strategies to model the cavity were tried (Planck tried for months, right?) so it wasn't just down to R&J having a flawed approach. It does make one reflect on how to classically model the cavity walls (or a a non-enclosed black body) as an IR/visible/UV "panel antenna". In short, R&J's decision to ignore the wall oscillators may have simplified the model but at what cost? Finally, it does seem alarmist that back in the day, just because the experimental results didn't fit this convoluted R&J conceptual model, that (some) physicists labelled it a "catastrophe"; there must have been some serious academic power politics, ulterior motives, alternative agendas, and ego tripping going on behind the scenes; especially as Wien's 1896 alternative classical model (the extension of his displacement law) was far closer than R&J. The fact that RJ's approach is given the status of "law" is extremely provocative given how poorly it adheres to the data; why would something so far off be called a "law" instead of just a failed hunch? Anyway, we're all fortunate to have access to such world class, thought-provoking content as this.

[@amitdangapcm1541]

Best explation of this kind of difficult topic. Thank you sir for clearing my concepts.

[@Ivan-mp6ff]

Mr DJ, you are inspiring. Thank you for sharing your immense knowledge bank with all of us. Cannot thank you enough.

[@akakichkhaidze1]

An example of how a great teacher teaches. Real life examples, stories, theoretical and experimental ideas and methods, taught by passion.

[@brotherstech3901]

Finally I thoroughly understand how Rayleigh jeans formula is derived. I have read many references but couldn't understand, but now I do . Thank you sir 🩷 Waiting eagerly for advanced quantum mechanics course.

[@kalki9924]

The derivation was a fairly tough one and you made it smooth as far as possible. Thank you sir

[@bismahaq6922]

just love your way of explanation! Thanks A Ton for making this topic comprehendible.

[@alfahad7433]

I was struggling to understand these topics and to dive deep into quantum mechanics for last two years. Then I found that you 're making a series on this topic. Please keep making the next lectures. I check everyday in your channel if you've uploaded the next lecture.

[@RuchiRuchismita]

Such a clear explanation of a complicated topic, which is not possible without clear understanding and passion, hats off to you

[@MisheckPhirichikwera]

Am really impressed with the way teach you simplify hard concepts of physics indeed

[@AMANKUMAR-ww9us]

A good experience, loved the details and mathematical approach is quit nice and compact. will wait for the next video in this series!

[@srizansutradhar5477]

My bad that I got this channel too late to see all the videos for my semester. But FOR THE LOVE OF PHYSICS, i promise myself will complete this series even after my semesters. I am getting knowledge and interested about quantum mechanics but I can't rush it for the sake of syllabus... WILL DEFINATELY WATCH IT...

[@luisbarros0910]

the best Rayleigh Jeans Law derivation i've ever seen, THANKS A LOT!!

[@swapnilgupta2112]

really liked the lecture sir your explanation and clarity of concepts are commendable, keep making such great lectures and we will keep loving it!

[@miinyoo]

Your explanation of black body radiation was exquisite. Very well done. Very much enjoy your videos. The eureka moment is at 24:30 however it takes all the setup to understand it. Unless you have already done it and I just missed it; explaining synchrotron x-ray radiation with the same depth and attention to detail would make for an equally great video.

[@carlosalbertoperesdesousa6077]

Simply the best explanation.... thanks

[@srimirasrimira9291]

Very thanks sir,the classes are priceless.❤

[@elhoplita69]

Hi, found this incredibly useful, thank you so much from Spain!

[@nd1748]

Dear Dibyajyoti - Love you for taking us along with your love of physics. What a fantastic journey. Many thanks.

[@Yellow_tiger_2023]

Sir you are the best ❤ , thanks aloooooot. It's night 3:16 am at 10 Feb 2024 , I have not slept yet . Surprisingly I don't feel sleepy either 😊. This lecture is just soooooooo interesting that I got too involved in this. And I'm going do the next video, it's like a suspence for me how & what plunk have been assumed that it solved the mystery of quantum physics.

[@SupriyaPradhan-dx1yp]

I have just watched 2.44 min but at the time of watching can't resist my self to type the way of your teaching is excellent 👌👍 need more teachers like u on you tube platform ❤️❤️ thank you so much

[@eternalthoughts-wu5lo]

Man....this is simply awesome and really SIMPLE

[@kevconn441]

Thanks for your great video.

[@christronaldo6106]

So beautiful so elegant,just explained like a wow🎉❤

[@MANISHKUMAR-ck3rc]

Wow man hats off to you,I can even pay for such a quality lecture to watch🎉🎉🎉🎉❤❤❤❤,awesome teaching.

[@Toji625]

Your videos are always great, please never stop making these kimda videos

[@siddharthsrivastava7492]

Very beautifully explained

[@md.mizanurrahman1643]

thank you sir for your wonderful explanation

[@Mr_Blaacck]

Thanks a lot sir!

[@sandeeppatidar1106]

Best video .Thank you sir

[@4711]

Nice explanations, clear language and amazing handwriting and drawings. Keep going sir

[@haiderabbasshah7674]

Thank God u uploaded this

[@naveedArt13]

Thank you sir this is very helpful for me

[@elamvaluthis7268]

Very nice explanation 👍👍👍.

[@rebanathpegulearner1252]

Sir I always waiting for your video lecture.. After your lecture series on Quantum Mechanics 🥰. Thank you so much sir🥰.

[@user-vy5hf4ei1x]

Thank you so much sir

[@shivukumarpradhani]

Very helpful Sir, Could you do more on Quantum Mechanics ?

[@SujanDas-zb7fj]

Waiting for the next video.. please upload more.

[@robiraufson5757]

Thanks a lot sir❤

[@xbrlinfinity9399]

I didn't realise the derivative of the formula for the volume of a sphere is the formula for the area of the sphere. I got confused when dV was written as = 4πr^2 (the formula for area) dr. I get it now. Going back and listening again I hear professor actually say this ... Volume = area X delta radius (paraphrase).

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Emversity's courses provide practical skills that are applicable in real-world scenarios.

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I didi not feel time watching this amazing video. You are truly gifted.

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[@user-fm2fq6qx8l]

Welldone sir😊

[@ridhikachhabra]

After a long time, our find ends here. 🙏 🙌

[@anasfarid2492]

Thanks ❤️

[@thirugnanamn8358]

Very good!

[@apoorvmishra6992]

At 30:33 you said that each EM wave is associated with 2 distinct polarizations (i.e. the perpendicular ones) and hence multiply by 2, but doesn't it neglect the contributions from the polarizations between the two perpendicular states?

[@abdurrauf7525]

Sir, kindly add Wein's distribution also to your playlist. Thanks

[@drivingmaster5809]

Really good👍🎉❤

[@MohithVenkatesh-ke3tr]

superb

[@zaikindenis1775]

Thank you for the video! At the begining we are talking about energy per time per suface area, but at the end we derive for per volume? And one more quesion, how to generalize the result obtained for a cube to any volume with any shape? Thank you!

[@FortheLoveofPhysics]

The experimental observations are for the cavity "hole" hence we speak of per unit surface area. But the theoretical calculations are for the cavity volume, hence we take per unit volume. But it should not be an issue as the radiation coming out of the hole is just a sampling of the cavity volume, so what is true for the cavity radiation per unit volume, should be the same as surface radiation per unit surface area

[@gok_dogan]

You are the second milestone of my physics lessons . if you wonder who is the first ? Walter Lewin 's Vibrations and waves lessons.

[@xbrlinfinity9399]

As an intermediate step, the Raleigh-Jeans law calculates the number of times each frequency fits an integer number of times between two surfaces as standing waves, but would not the formula overstate the number of standing waves because most waves leaving the first surface would reflect off the second surface at an angle and be absorbed by a third surface for the third surface not being an integer number of nodes away from the second?

[@alvis7132]

If someone is interested, this derivacions is in the eisherg book

[@marvynhsu9696]

Thanks for the excellent content. I want to ask about the wave function which I am very bad at imagine it intuitively. At 19:20, why k^2 = kx^2 + ky^2 + kz^2, is there any simple direction of this?

[@griffithfimeto3387]

Keep going I am gonna learn QFT without understanding blackbody ! So sad waiting for you

[@drazaq]

Frequency range means a specific frequency or a range of frequencies ( for example 10 Hz to 15 Hz)?

[@OkAnup]

you said blackbody radiation curve is independent of the material in the beginning but used the electrostatic property of metal to explain why standing waves arise from the cavity in deriving rayleigh jeans law; shouldn't it be independent of the conductivity of the blackbody?

[@dauhalanyeuvatly]

Why at 14:32 the number of possible frequency is N(f).df and not only N(f) only? What if N(f).df is not integer?

[@storyomg216]

Please thermodynamics pr bhi video banaiye sir please

[@katiyarrishabh093]

Aanghe ke lectures kab aayenghe sir

[@sushmamishra9268]

Next lecture please 🙏

[@haiderabbasshah7674]

Sir plzzzzzzz be regular

[@harry-ho9ti]

Waiting for the lecture since a week. Pls increase the frequency of lectures sir.

[@FortheLoveofPhysics]

I will try to upload the next ones quicker

[@haiderabbasshah7674]

@@FortheLoveofPhysics thnxx

[@pauldirac6243]

Don't rush the man. Every video is a gift not a right. He's got a plan.

[@benstallone6784]

@@FortheLoveofPhysics Please sir don't listen to harry lol This was a beautiful presentation - probably the best on the topic I only hope you keep up the superb quality even if we have to wait a little longer

[@abhijitshaw9431]

wowww wowww wowwww....Hence proved ,, the more you wait the sweeter the fruit you get.....thats a niceeeee explanation sir...thanks a lotttt sir!!!!!!!!!!

[@iitian-or1zc]

EVEN MY PROFESSORS AT IIT DELHI DID NOT TEACH SO WELL!

[@pranjal1698]

please tell us why we exclude the negative integer values and only consider positive integer values.

[@noelomaolchraoibhe3911]

Probably because "less than zero" standing wave peaks is a physical impossibility; at least one peak is the minimum to have a "wave", right?

[@adityamalviyaadi4116]

Biggest fan sir ❤

[@sandeepchauhan4411]

i din't understand why we are taking x=0 and x=a as kind of 2 fixed points for standing waves to have

[@FortheLoveofPhysics]

That is where the walls of the cavity are placed

[@kanaktiwari2906]

Equipartition me 1 D ki energy KT h but 3d Nihal rhe h To 3KT hona chahiye ?

[@FortheLoveofPhysics]

The harmonic oscillators are 1D, so it's KT

[@abdurrauf7525]

Sir, at the time around 29:27, it's the first quadrant or first octant?

[@manansharma9164]

First octant (+x,+y,+z)

[@FortheLoveofPhysics]

yes, I mispoke. It should be 1st octant (as it is in 3D)

[@abdurrauf7525]

@@FortheLoveofPhysics thanks sir

[@storyomg216]

Sir please makes a video about thermodynamics....plzzz😢😢😢😢😢😢😢😢😢😢😢😢😢😢

[@KylianMbappe07303]

29:40 why would it be 1/8

[@TPMmusicLive]

Wow❤

[@MANISHKUMAR-ck3rc]

Damn ,that's called teacher

[@djchandu1984]

Sir please upload quickly lectures 🥹🥹🥹

[@Pkshah420]

Hold your horses bro..... excellent works take time

[@ZR333]

Yes sir

[@samiranguchhait350]

yes sir

[@amritsagarkar7899]

​@@Pkshah420 where the horse came here. Out of nothing you bring horses in physics discussions. You should say don't be in a hurry bro!!!!

[@aiseop31415]

​@@amritsagarkar7899Rip English

[@gulkhan6499]

Sir Compton effect

[@sharad9176]

Sir aap Hindi me bola kijiye please

[@marspalk7611]

He speaks in English so wider audience can be reached.

[@theishu3512]

Sir I HAVE A QUESTION THAT, ARE YOU GOING TO TEACH COMPLETE QUANTUM PHYSICS OR SOME PART OF IT .???? Please please ANSWER 🙏🏻

[@pauldirac6243]

Why don't you try watching the first video in the series