The Mystery of Light - Walter Lewin - July 19, 2005

[@flxblflyr]

When I was about 10 years old, maybe 1970, my Dad saw a notice in the paper, of a visiting scientist at Furman University, near our home. We went see his public lecture on X-Ray astronomy, not knowing what to expect. The charming, enthusiastic young lecturer told a wild, absorbing tale of his adventures with balloon-borne telescopes in the Autralian outback- and what they had learned about X-Ray objects- neutron stars, black holes... It was thrilling; I was rapt. I never forgot the feeling of being at that lecture. I went on to become an electrical engineer, and never lost my love of the science. Forty five years later, I found Lewin on you tube, as I was preparing for teaching some high schoolers. I started watching his lectures- which are exemplary. After quite a few, I came to his last lecture- where he reminisced about his early research at MIT. X-Ray telescopes, ballons, Australia. Oddly familiar...When he showed the photos, I suddenly realized I'd seen those pictures before- when I was ten. The guest lecturer who inspired so much was the young Walter Lewin. Thanks, Dr Lewin.

[@lecturesbywalterlewin.they9259]

hello Stan. I recall that I gave 5 lectures at Furman every January for 5 years in a row. The lecture that you attended may have been just one lecture before my January routine returns.

[@jjtompson5914]

@@lecturesbywalterlewin.they9259 I have question if i may? How can both statements below be true? Knowledge of the Which Path collapses the Wave Function.....................(DCQE Experiment) Knowledge of the Which Path does Not collapse the Wave Function......(Observation of single slit diffraction)

[@81giorikas]

@@lecturesbywalterlewin.they9259 Didn't Einsteing himself actually hinted on the answer to the double slit experiment anyway? Not so much of a mystery the way he thinks of it.

[@maxmax0]

Wow! Quite a story!

[@Meninx87]

Professor Lewin you are truly an inspiration and i'm grateful to you for the work you've done.

[@lecturesbywalterlewin.they9259]

+Meninx87 Thank you Meninx

[@sosheeanand3537]

Dear prof Lewin I am a researcher with PhD in Biotechnology. I ran out from Physics and Maths because it was so difficult to understand things. Ironically I landed in a Physics lab in Grenoble, France for my post doc (protein biophysics). I saw your "last lecture" first and my mind blowed as things were explained so simple. I started watching your lectures every weekend and now I am confident that I understand things. Extending this now I am also learning astrophysics and calculus. World (at least for those countries with poor education) need inspiring teachers, I blame my country for not giving this kind of basic education. It is more important not to destroy the interest by bad teaching but this is what going on everywhere. Now I can inspire my 7 year old son to study Physics and Maths..

[@lecturesbywalterlewin.they9259]

+Soshee Ananda Thank you Soshee. I am delighted that my lectures have changed your life. I hope your son will also learn to appreciate them in time.

[@aruntejamarakani6817]

Lectures by Walter Lewin. They will make you ♥ Physics.

[@animations3193]

Man thats ur fault ,dont blame india

[@mitochondria7321]

@@animations3193 yes ,not every indian physics or maths lecturers have ability to lecture like this

[@animations3193]

@@mitochondria7321 man don't think like that, there r so many proff's who can do teachings better those mit proff . Im not blaming mit but some concepts mit proff not explained better than my proff.

[@Todenkopf09]

I wish my Physics professors had this kind of passion. I love seeing the methods for discovery on these topics, the reasoning behind why they attempted different experiments. One answer can lead to so many more interesting questions.

[@lecturesbywalterlewin.they9259]

Kurushimu :)

[@muhammadirfankhan997]

Sir Walter Lewin, I have made a habit of watching at least one of your lecture a day and getting amazed by the beauty of Physics, thank you so much. Though I remained a regular student of Physics from schooling to university but understanding it to its core was never this simple. Wish I was able to take one of your lecture if not all. Also, I am buying your book "for the love of Physics" as a reminder of your great work in the field and in the meanwhile requesting the administrator of this page to upload every lecture of yours here on youtube. Thanks and stay healthy. :)

[@lecturesbywalterlewin.they9259]

+Muhammad Irfan Khan Dear Muhammad. Thanks for your kind note. There are 284 videos on this site. That will keep you busy! Good Luck!

[@ahsanrubel2869]

I was not a student of physics... We were so unlucky that we never had teachers like Walter Lewin. It’s surprising that I found myself learning physics because of this kind of teachers.. Long live sir Walter Lewin..

[@amisharawal3967]

Hats off Professor Walter Lewin !!! I m in 11th standard, taken PCM (science - A group), very interested in and fascinated by physics (especially quantum).... I clearly understood 95% of all your lectures........... Very inspiring, and in a nutshell, I can say, your lecture is like 'Physics Made Simple'............... Thank you sooooooooooooo much for sooo very much interesting and inspiring lectures............

[@nasrinzhakfar2040]

It's just the beginning of the video and i'm realizing many things. I am like ohhhh! I understand it now! Everyone has a different learning style and understanding method. The way you explain things simply so that a high school student can understand too, is just so good and is exactly how i can learn. Thank you so much. I will pray for you.

[@tylershepard4269]

Hi Professor Lewin I’m an undergraduate in Electrical Engineering studying RF and Microwaves. Thank you for helping me to love light!

[@christopherwoodcock8535]

Second time I’ve watched this great lecture. Since the first time I have purchased a Linear Polarisation Filter of my own. Fascinating stuff. Thank you Professor Lewin. Inspirational as ever

[@satyanaidu4]

A bad teacher complains, an average teacher teaches, a good teacher explains, a great teacher inspires! I'm writing this at 4am, you sir have made me decide to pick up my physics textbook again at age 36! Thank you!! :) p.s: I love it the way you say " this is an illegal question!"

[@quantum7401]

+ Illegal question

[@cmetube]

Great lecture Professor Lewin. Beautifully organized and incredibly poetic

[@chekystar]

great teacher i am not student of physics but i watch your lectures anyway because you make it interesting and because i love to know how the world works. thank you :) i learned a lot from you. keep on the good work

[@kenantahir]

you are an awesome teacher. i only wish i had teachers like you back in school days (20yrs ago).. maybe then i would have passed my physics exams and would have had interest in them back then... see this teacher knows how to break it all down to the last bit.. he practically unravels it all for you to understand!

[@susansutton1712]

thank you for making complex knowledge easy to understand and for making it easy to access your lectures. Much respect to you Sir Walter Lewin 🖖

[@directedbypuma]

You make it so understandable, thank you! I am a licensed ham radio enthusiast and this lecture puts it all in perspective for me. I think a particle is also a wave but at very high frequency that you might not see its wave effects in nature.

[@Rambofpv513]

I concur, I think the frequency becomes so high that it becomes Circular producing matter

[@lalropuiachinzah3335]

Since i watch this lecture video, now everyday i watch at least one lecture during lockdown, I highly appreciate and love your teaching,Sir

[@manishk45]

I would like to meet this #Physicist once in life. I love his lectures.

[@gopisingh1630]

love from india . i live in a village in punjab ,india . here , everyone wants to go to U.S , just to earn more money, by doing labour . but i would like to go there as a theoretical physicist . thank you sir ,for helping me lose my virginity in physics.

[@soumenatha7288]

😂

[@simonmasters3295]

​@@soumenatha7288I found the sentiment rather challenging...do you suppose she or he got to the US?

[@joseg.matamoros2847]

“Lose my virginity in physics” is wild

[@vik2377]

Kudos to you my friend. .keep it up and you would be successful

[@sharkgaming9756]

​@@simonmasters3295b

[@mindscraped]

i posted a question about one of his light demonstrations and asked a question about the light being a wave or particle and the observer effect . You guys gave me an amazing answer i have never heard before thanks. But i am commenting about it here about that post because i cannot find it anymore. I just know i got a response with my notification . The point is thank you so much for answering my post . the answer was amazing

[@bradjunes1610]

It was hard to turn off what I do at age 70 and get back into thinking, but enjoyed your thoughts. I've tout many with a simpler approach of more one on one. The masses won't understand at the speed you teach. But I loved it. Much thanks.

[@lecturesbywalterlewin.they9259]

:)

[@lbomcarvalho]

Prof Lewin, your performance I take as a standard performance of somebody that loves physics, science, teaching, ..., my sincere congratulations.

[@lecturesbywalterlewin.they9259]

:)

[@keithlillis7962]

Excellent stuff and so glad Prof Lewin mentioned in a little more detail the findings of Quantum Mechanics, as up to that point he had me convinced that light was just a wave :-)

[@das250250]

Walter not only teaches at the highest possible level and professionalism but his black board layout is so organised , writing is legible and drawings are just so well drawn. In my opinion , he sets the bench mark for lecturers ..

[@lecturesbywalterlewin.they9259]

thank you :)

[@jessemontano6399]

Wow, it's so awesome that the professor answers so many questions/comments. That's legend!!!

[@suecondon1685]

For me, light is the biggest mystery of all. Thank you, this was fascinating.

[@lecturesbywalterlewin.they9259]

@@PreCognition777 yes, and since the moon is made of green cheese we will even be able to eat the moon

[@seminolerick6845]

Just found this awesome presenter of info, yesterday. On top of everything else... never saw anyone else draw dotted lines on a chalkboard like him ! Silly, I know... but a great, effective tool in his tool box !

[@suecondon1685]

That's another mystery! 🤔 How does he do that!

[@alimukhtar4759]

Hello professor Your lectures are helping me and many other physics lovers to understand the nature quite easily. I am lucky to be able to get your lectures online Wish you a healthy life

[@ajaykumarmaruvada9113]

Dear prof Lewin a very happy teachers day. We wish India should have a guru like you to explore our horizons and to know that science which hides truth is also curious and fun. Thank u once again . HAPPY TEACHERS DAY. !!!!!!

[@lecturesbywalterlewin.they9259]

thank you very much

[@dalenassar9152]

Prof Lewin. Your presentation: "THE MYSTERY OF LIGHT" was fascinating--thank you. I think I have an explanation on why the small audience could NOT hear a VERY low volume with the destructive interference of the sound waves emanating from the speakers (while you did in private). PERHAPS THE SOUND IS REFLECTING OFF THE SWAYING, GROUP OF PEOPLE--THUS SCATTERING THE NODES SOMEWHAT! Thanks for everything--you will never know the enjoyment you have provided me. Dale Nassar, Amite, Louisiana.

[@lecturesbywalterlewin.they9259]

yes sound is sometimes problematic for that reason

[@sangitasinghal3249]

I can literally hear the destructive interfere on my smartphone. At .. 57:09 and constructive at 57:13 Thanks Professor Lewin, you really made me to ❤️ Physics.

[@miz2k188]

Ye bro me to o Thanks for this

[@taherzahrani201]

Even old people attend professor walter lectures , this is a proof of how great teacher he is ❤

[@rajeshkaushik5223]

I loves Ur all lectures, it's very adorable.u r my best teacher of physics

[@lecturesbywalterlewin.they9259]

Thank you!

[@davebewshey1549]

Imagining the multitudes of minds that will make future scientific discoveries this brilliant man has inspired is astounding. Proof that one man's life can change the world. Even if he is not the next Einstein knowing that he may have inspired them and furthered human advancement is amazing and beautiful

[@aaronkellner620]

Very well put together lecture. What I have always had trouble with is the claim that light is some sort of EM wave. The implications of that simply don't clearly manifest as one would expect. My opinion is that there are clues that light is more than that. Much more.

[@MojeAdeyemo]

Well done Prof lewin 👋👋 You're one of the best physicist I've ever seen in this century

[@lecturesbywalterlewin.they9259]

thank you

[@swapnilsaha8143]

Dear Professor Lewin I am an Indian Engineering Student... From Childhood I 've always wanted to be a physics teacher..... Its really Hard in my country to Catch This type of dream....Here this system doesnot look How much you know rather it looks How much U have got marks....they will not see... Who has understood and who has only memorized the Whole page books... research...I've had So many questions...I've resolved...many...and still have some...Sir, U probably donot know.... Everytime I see your lectures and remember your picture.... I gain my motivation to get a Stable post in research....Even though I had to choose engineering...because of Our Education system....but Still If I have to go to particle research path...I have to take a very Very long path....And I will obviously succeed...one day....Your Lectures...changed my perceptions and helped me get my motivations back...everytime I've been pushed apart from physics.. Thank You Sir♥♥♥♥♥♥🤣

[@88Conqueror]

Bhai ab kaha ho ap

[@RaivoltG]

I wish you were one of my Professors! I don't understand much of what you discuss but you are so enjoyable to watch, and I do grasp some of what you say! You are pretty funny too! I liked it when you threw "photons" to your students! The egg on your shirt is funny as hell too! I wish more professors were like you! I'm sure that you are making more of an impact than you are aware of! You will definitely be directly responsible for many good things to come. Your students will be the ones to make discoveries, as I'm sure you have and will continue to. Thank you for the videos, I love watching them!

[@segalindoa]

The guy sleeping at 27:27 is priceless (also the way the professor draws the dotted lines. That's chalkboard mastery).

[@nobodyyouknow9839]

My father give me telescope at age 15 on my birthday 😅..... As I asked him for that later he asked why I am so addicted towards science and physics specially then I answered you don't meet the legend Walter lewin that's why you are talking like I meet him daliy on his KZbin channel and get inspired . Your every lecture is a masterpiece .... I am glad that camera and internet make your lectures alive forever . Wish that I can also witness the great Richard fyemen 😢😳. Love from India sir

[@lecturesbywalterlewin.they9259]

lucky you!!

[@hewhenthehe3722]

Professor Lewin, can i just say the wave you drew at 6:02 was beautiful

[@amisharawal3967]

And yaa also I have a question......, In some of the many versions of the double slit experiments performed by many physicists, many used electrons, and some of them used single electrons..... But according to the uncertainty principle, we cannot measure both the position, and the momentum of any particle at the same time, accuretely...... So how can we manage to produce (eject) only single electrons of specific momentum, without first locating them in an atom, and in turn ruining the certainty in its momentum ( which is what we actually wanna be very certain about, especially in the quantum eraser version of the double slit experiment) Pls answer and plsssss correctme if I m wrong........ And once again thank you Professor for the lecture........

[@kss4282]

Please answer me Sir. I am from India. I'm crazy about physics. I have a doubt. If I turn on two lasers (say A and B)facing each other simultaneously in vacuum. Then the velocity of 1st photon thrown from A with respect to the first photon from B shouldn't be half of c. How is it constant?

[@studyingchannel2328]

I also want to know .please like my comment when teacher give you the answer. So I can be notified.

[@ramonchan9732]

I like the fact that professor Lewin tried to explain high school physics to those kids.

[@joannadrozdz3848]

Wonderful lecture, thank you.

[@Eztoez]

Professor Lewin, you remind me of Richard Feynman: both superlative communicators and deeply passionate about Newtonian physics & QM. Thank you.

[@lecturesbywalterlewin.they9259]

:)

[@fjs1111]

Not a typical professor, this is a different scale of talent right here.

[@davidwilkie9551]

Life is Quantum Mechanics, but that is a statement about function, not a description about the lifeforms.

[@shadowmedow4028]

sir ur lectures are damn inspiring.....whenever i wtch them i find a great diff in my teachers saying and urs...#inspiring they don't give tht chance of questioning topics....they say either ur oversmart or dumbo....and i got depressed due to this reason still i couldn't stop it ....u r a living inspiraations topics r well revised here thnks sir !!

[@clayz1]

He’s given this lecture hundreds of times. Probably. Very good, I have seen it a couple of times.

[@utuberaj60]

The part of this lecture stating that it is Heisenberg's Uncertainity Principle is behind the fact that electrons, atoms,molecules move continuously and have energy. The same applies to the billiard ball too with an assumed uncertainity limit i.e. h/2*piset as 1, as seen by "Mr. Tomkins in Wonderland"- an entertaining science popularising book by astrophysicist George Gamow. The fact that billiard balls or similar macrocscopic objects don not wiggle around spontaneously again due to the insignificant effect of Heisenberg's Pricnciple on large objects which we encounter in everyday life. I want a bit more of how this Priniciple was derived from De-Broglie Principle and Schrodinger's Wave equation. Hope the professor can show us this too sometime.

[@malvikaawasthi2457]

Does heat+heat also can give no heat if destructive interference is applied please like this as much as so that prof walter lewin can answer this question

[@lemont2005]

Hello! Sorry for this inocent/strange question that I´ll ask: Did anybody have ever try to collide one eletron against one proton? What happened so?

[@lecturesbywalterlewin.they9259]

Good question. In principle this can be done, but you would learn very little from just one such such an interaction. Experiments are therefore always done with large amounts of electrons and protons, not just 1.The results vary greatly depending on the energy of the electron. . "1) Elastic electron-proton scattering: the electron and proton just "bounce" off each other under some angle theta. By observing the cross section of the scattering versus the theta angle it was shown that proton is not a point particle, but an extended object. 2) Deep inelastic scattering: the incoming high energy electron "destroys" the proton into a bunch of outgoing hadrons (mostly pions). By observing the cross section of this interaction it can be shown that proton is composed of pointlike particles. The electrons collide elastically with a parton"

[@kovanovsky2233]

Just to add from what I know, there is a research going on where scientists basically smash 2 protons (if I remember correctly) together and analyze what happens. And that's how they found subatomic particles (quarks, etc). Please correct me if I'm wrong.

[@prakharmathur9453]

I have 3 questions:- 1) Since proton and electron attract each other, then how will they bounce off each other? 2) What are partons? 3) Is the energy of electron in first case lower than that in second case?

[@lecturesbywalterlewin.they9259]

1. learn about QM 2. use google 3. question unclear

[@gh0stgl1tch]

@@lecturesbywalterlewin.they9259 if so then how light passes through glass. Just curious , I think of a lot but everything ends in a stand still

[@kiprutojunior9826]

The best physics lecturer of all time

[@H2x2x2]

Immaculate educator. Thank you sir. 🙏👍

[@luckynewman]

Dr. Lewin thank you for the videos! Awesome delivery. I have been trying to find an answer to the question how much uv light penetrates water (say pool water) I see a lot of sites saying that 100% of uv is reflected and others contradicting this. If you could shed some light on this question or maybe point me in the direction where i can learn more for myself that would be really cool. Thank you Professor Lewin and my girlfriend and i loved your book btw we got the audio version!

[@lecturesbywalterlewin.they9259]

+Brian Campbell Look at the absorption spectra which are available on the web.

[@khanyusuf09]

Sir you make physics look so interesting and beautiful exactly the way it is...your way of teaching gives me an insight of how the nature works rather than scratching my head on all that dumb dead physics equations spread all over my physics notebook..you taught me the beauty of those equations...so thank you sir...stay healthy...😊

[@lecturesbywalterlewin.they9259]

that's why my lectures are world famous! :)

[@fransb8543]

Geweldige lezing, zeer boeiend en leerzaam. Blij dat ik uw kanaal heb gevonden.

[@lecturesbywalterlewin.they9259]

mooi zo!

[@sahilkumar-jn8vb]

Excellent lecture with clear explanation sir u r great Watching your lecture I m inspired how to make physics more and more interesting before this physics was just a discription of heavy maths and digest them anyhow to pass to clear the exam Nice sir

[@MihaiBadicioiu]

Wow - a new "episode" I did not knew.... thank you!

[@lecturesbywalterlewin.they9259]

Mihai Badicioiu This site contains ALL my lectures. My 94 course lectures are in much higher resolution than anywhere else. They also show problems and exams (and solutions) and Lecture Notes (pdf files below the videos). Not all my course lectures have Lecture notes. Notice the many non-course lectures including my 8 lectures that I gave for Japan TV (NHK) these are in HD!

[@SamuelDaniel01]

Always delivering explicit lectures

[@mavis2701]

i've always loved physics, and Mr. Lewin is a great example of why

[@lecturesbywalterlewin.they9259]

:) 😊

[@JimCarver]

Oh good, this one I haven't seen yet. I've watched all the lectures from the three courses, many multiple times. I always catch something I didn't notice the first time around. I just watched your farewell lecture at MIT again. That was kind of sad. I bought your book and am going to give it to my grandson when he gets old enough. That may be pretty soon. He loves science.

[@lecturesbywalterlewin.they9259]

+Jim Carver Hello Jim - If you have seen all my course lectures you should also consider to watch my 8 lectures I gave for TV (NHK) in Japan. The version I have posted on this channel is in English. It's very nice that you will give my book to your grandson. If you send it to me I will sign it and return it to you.

[@JimCarver]

Wow, that's great, Walter. I'll do both! You know, to tell the truth, I had already loved physics...but you made it a lot more fun. :) Thank you and I wish you good health!

[@truebeliever174]

That's the lecture when I was 2 years old. And I am seeing the lecture in 2019. Thanks to KZbin.

[@lecturesbywalterlewin.they9259]

no need to watch it again!

[@Siddigfadul]

I am a physician, Surgeon General, but for very unknown reason I am addicted to these lectures, can any one explain??

[@drdeak]

Particles or waves, hey professor Lewin what about David Bohm's theories on the argument?

[@urk_1091]

Sir you really are an inspiration for many students, I never thought of becoming a teacher but watching you I have the desire to become one. The way you're teaching, giving out your knowledge to the students is remarkable. I'm saddened that not every teacher is passionate like you, often it's not the sibject which is hard or boring but it's mainly the teacher how he's giving the lesson.

[@lecturesbywalterlewin.they9259]

YUP! so true

[@urk_1091]

Sir you have a life time experience. I have a question, regarding any study. I have the feeling that one's knowedge cant just exceed by reading books, but oftend things are learned through experience when you try those things and when you can relate those thing with in real life, only then stuff in the book makes sense. but again the way education is given is at a very fast phase, often ignoring the real essentials of studying ( understanding instead of memorizing).

[@lecturesbywalterlewin.they9259]

what counts is not what you cover but what you uncover! That's how I teach.

[@jondeere5638]

I stand corrected, I went back over the videos on Newton and saw why particles and corpuscles cannot be used (as some do) interchangeably. The key was the light experiment.

[@vigneshkumar9378]

Sir i am from India, in my college classes seems to be so boring and sleepy, faculties expel what they get from textbooks, it doesnt really take student into his imagination or unveil the mystery of the subject. Your classes are really fantastic sir.

[@anuragmishra2245]

Sir, Why do we use constant of proportionality ?

[@chillhopnation7635]

I think why the amplitude doesn't have affect on velocity of wave of sound?

[@dgtamil492]

sir,i like ur all the lectures ,it is very awesome ...............................i love so much ur art of teaching..........

[@lecturesbywalterlewin.they9259]

:)

[@santhosh.thatikayala7479]

Thanku very much sir...u make me love physics yjrough ur lectures

[@das250250]

@12:40 I don't swallow that a vacuum is empty and that electromagnetic waves are travelling through nothing ... Space expands and must know how to expand and can pass on this expansion across the universe with gravitational waves . Space must contain structure,at a minimum the physics of the fields. Vacuum must contain energy and must have some structure to be held. A question might be can an em wave travel beyond space time which as i understand is no, therefore spacetime is needed to allow an em wave to exist . Then what exactly is the relationships between spacetime and magnetism and electric charge . To date , we must first have electric charge for electric field and and movement of that charge to create magnetic field. The creation of matter from the spacetime which creates the electron can produce these field disturbances.We must have a model of the electric charge to spacetime interaction which currently we call field theory ,with fields that just exist?

[@lecturesbywalterlewin.they9259]

I suggest your read up on "inflation"and GR.

[@das250250]

@@lecturesbywalterlewin.they9259 Thanks Walter

[@annapurnam.1603]

Sir i am Nayantara Sir this the lecture about which i wanted to ask Sir the timing in the lecture is 8:11 i.e 8min and 11secs My query was As u said in the video "now if I move my hands up and down here and these were strings in capital T secs, and if this disturbance moves with the velocity v, then the disturbance has moved v times T But i want to ask Why its v times T, why it can't be v divided by T?

[@lecturesbywalterlewin.they9259]

if your car drives 80 km per hr (speed V) and it does that for 2 hr (T) how far has your car driven?

[@annapurnam.1603]

@@lecturesbywalterlewin.they9259 Sir in this case, since speed is equal to distance by time then distance is equal to speed times time, that is because we know speed is distance by time and we just interchange the equation, but here what i meant is Ok i will give one more example, Force is mass times acceleration right, but here in reality when forve is acting does mass and accleration gets multiplied or what is happening. In this way i wanted to ask that question also that velocity times Time period means exactly what, they get multiplied when there is propogration of waves. Iam sorry my question was not clear.

[@lecturesbywalterlewin.they9259]

@@annapurnam.1603 If the wave travels with speed V than after T sec it has moved over a distance VT. If T is the period of the wave then VT is the wavelenght. This is my last msg on this issue.

[@blancaroca8786]

At 1.04 we see interference between light waves from a double slit. It is really good to think about what you would get here with only one slit open. Instead of the 9 or so spots of maximum intensity we should get a long swathe of light more or less covering the spots and filling the gaps between with a total light power of about half as only one slit rather than two. We were lucky as we got to do these experiments ourselves in school lab in the 70s. Much better than seeing exagerated cartoons in a textbook. We were lucky our school spent next to zero on textbooks and instead bought some simple apparatus which turns out cheaper and better for learning.

[@chazguthrieful]

Is the double slit experiment interference due to partical entanglement?

[@Learner-u6j]

Hello sir i'am from india ,, sir u r a great teacher ,, a real teacher who teaches students from his heart ,, sir in my locality teacher feel shame to teach these basic definition and concepts ,, and if any student ask these type of things they think that this child is dumb n insult him. That child will not able to ask question from next time. Aslo sir u r such a great physicist , even u taught students all concept like student is starting from zero. U r great sir ,, plssss plssss plsss launch a course on physics of 11 & 12 standard b/c sir class 11 & 12 are the pillars of our study career ,, but indian education system not prepare this pillar to stay strong for future ...thank u sir We love u sir 😍😍😍

[@jacobmerz2803]

I wish your lectures were captioned for Deaf folks like me.. I watched your last lecture and I was blown away.

[@lecturesbywalterlewin.they9259]

+Lectures by Walter Lewin. They will make you ♥ Physics. Jacob all 8.01x lectures have subtitles. We are also working on 8.02 subtitles (it's time consuming).

[@glen-draketoolworks7186]

The "orders" appear to fade as they move away from the zero order. Is that really happening and if so, then why?

[@princeacez5905]

Can someone please explain how you derive the expression for roughly the number of nodal lines(2d/(wavelength))-39:17

[@dhakshan]

That would be in class 11 or 12 text book right?

[@0Erag0n]

This just shows that Great teachers, make the students. If my teachers was this inspirational i would have loved going to school, and my field of interest would have been much wider.

[@lecturesbywalterlewin.they9259]

+0Erag0n Yes it's cry sad that poor Physics teachers ware the reason that so many students hate Physics. The teachers blame the students, but only the teachers are to blame.

[@JimCarver]

+Lectures by Walter Lewin. They will make you ♥ Physics. Sometimes, or maybe even much of the time, it may be the grad students who put the student off. I remember this one back in college, he didn't want to teach undergrads, he wanted to show us how much smarter he was than us. I've had a few experiences like that in the sciences.

[@FeigerNazi]

How do waves anyway know in what measures they have to bounce up and down again, the so called frequency? And what force keeps waves, or them being a particle, not exceeding the upper and the lower border of that frequency? They are not inside of a tunnel, or are they?

[@lecturesbywalterlewin.they9259]

bcoz waves have taken courses in Physics

[@oerangoetan]

De ideale leraar. Geweldig meneer Lewin. Groeten uit Schchchcheveningen

[@aashik9625]

New to your channel professor Lewin ❤️. Take care of your health professor .

[@em_universal]

Awesome explanation!

[@Jim-tx6se]

57:32 I've tried this at home and it works!!

[@system.machine]

An amusing note. During the "find the dead spot" section, you could hear it as the camera panned across.

[@nagendrasanapalli3200]

Dear professor, I had a doubt that the water wave is travelling by dropping a stone in a river and the sound wave is generated due to the vocal chords and how's the light wave is travelling. And what is the disturbance behind it. Can u please?

[@SanjayMishra-ee7jr]

Hllo sir.. We all say that speed of light is universal constant. It does not changes in any frame of reference. But if the velocity will not change the refractive index will 1 for every medium. Soo plz tell velocity of light is absolute in the universe or it is variant.. And why?? It should not be constant in any frame of reference?

[@lecturesbywalterlewin.they9259]

it was *postulated* by Einstein that the speed of light in vacuum is independent of the frame of reference. This has been observationally verified countless times.

[@SanjayMishra-ee7jr]

Thanku sir thanku very much

[@SanjayMishra-ee7jr]

Planets revolve around the sun in the elliptical orbital.. Their orbit is also fixed. But what pluto why does it not have a proper Orbit? Why it cuts the orbit of neptune?

[@SanjayMishra-ee7jr]

And also sir does our universe and solar system has magnetic field

[@lecturesbywalterlewin.they9259]

Pluto's orbit is proper. It's a Keplerian orbit.

[@dalenassar9152]

Prof Lewin, I have just watched your lecture on the uncertainty principle with the demo of the light spreading as you narrowed the vertical slit. I have been wondering: What would happen if, instead of a shrinking linear slit, there was a shrinking circular opening (such as an iris) that could shrink all the way shut. What would the light pattern look like as the uncertainty spreading began???

[@lecturesbywalterlewin.they9259]

>>>What would the light pattern look like as the uncertainty spreading began???>>> yes, of course UP always holds.

[@TheZooman22]

These lectures are quite enjoyable.

[@bastinbajiojob564]

Sir, I am currently a graduate student, and I need some serious help. I have always loved physics, and I have watched all your lectures. I actually felt the "love of physics". You have told that "A teacher who makes physics boring, is a criminal". Well, I am trapped between criminals. My professors out here are making physics like eating raw meat. I am unable to tolerate this. Kindly advice me how to survive in such an environment, and to keep the beauty of physics evident for me. How should I teach myself the right way to learn physics ?

[@lecturesbywalterlewin.they9259]

Watch all my 94 MIT course lectures. Start with 8.01, then 8.02, then 8.03. Do all the homework and take all my exams. Homework and exams are posted below the video thumb nails. Take 2 full months to do ALL of 8.02, then 3 full months of 8.02 and if you still have time left take 4 months for 8.03. This is a MAJOR commitment. You will have to spend on average every day 2 hours on this - YES EVERY DAY. *I guarantee you that you will then NOT fail your Physics exams*

[@faisalkhatri1813]

awesome.. Thank you sir.. very well explanation.

[@tensor-records]

Sir, I am really grateful to have come across your videos. They really inspire me. I always liked physics and loved how it manages to develop a counter intuition for a thought. I would like to ask you a question, what are quantum fluctuations exactly?

[@lecturesbywalterlewin.they9259]

use google

[@tensor-records]

this is so far the best reply I've had. XD

[@lecturesbywalterlewin.they9259]

In quantum physics, a quantum fluctuation (or vacuum state fluctuation or vacuum fluctuation) is the temporary change in the amount of energy in a point in space, as explained in Werner Heisenberg's uncertainty principle. This allows the creation of particle-antiparticle pairs of virtual particles.

[@tensor-records]

Lectures by Walter Lewin. They will make you ♥ Physics. thank you very much sir :)

[@sayantansaha2308]

I have a question sir, Sir we know by the definition of wave that, it is the disturbance caused in a particular medium. So if it so than why are light said to be a wave if it is not flowing through a medium? And thinking a wave without a wave seems very very non-intuitive, at least for me. Sir don't you think the concept of Luminiferous Aether or Ether is a true concept to hold the wave nature of light????? Please reply me something Sir......I am eagerly waiting for your answer!!!!!!!!!!!!!!!

[@lecturesbywalterlewin.they9259]

use google

[@sayantansaha2308]

@@lecturesbywalterlewin.they9259 Sorry sir but nowadays internet is full of junk, so I am not getting or I may not be able to find out the real source I am hunting for. If you suggest me something, it would be very helpful to me Sir!!!!!!!!

[@piyushmishra12a40]

42:20 Whats the reason for it... If

[@theshittybeatles5768]

I lost him at Hello and got it back at Goodbye.

[@kenantahir]

you are like that guy at 1:22:02 maybe youre the same guy

[@mandroid3219]

If sound requires air as a medium, and water waves require water as a medium, then what is the medium of light?

[@lecturesbywalterlewin.they9259]

good question. Our grandfathers called that medium ether. But we now know that the ether does not exist (famous Michelson Morley experiment). Thus EM waves can travel through vacuum. en.wikipedia.org/wiki/Luminiferous_aether

[@drsanjeevgandhi5365]

Can we see objects only because light rays reflected from object enter our eyes?.Also if every object reflects light then why can they form images like mirror do .Hope you answer this .Thanks

[@misaonthefly]

i would love to personally be in one of your lectures...