This website contains all my 94 course lectures (8.01, 8.02 and 8.03) with improved resolution. They also include all my homework problem sets, my exams and the solutions. Also included are lecture notes and 143 short videos in which I discuss basic problems. ENJOY!
i want all of them downloaded what should i do? finally love you and your lecture. unfortunately i will never get chance to meet you. i wish ................ may be in next life.
@@lecturesbywalterlewin.they9259 Sir can you please do something good for Indian viewers. Can all these lectures be translated into an hindi audio voice?
i think that is because of the filming is an digital signal, it has filming frency, so the signal has lost many stimulations received by your brain than the reality of native continueous signals.
I have a question regarding Newton's Explanation. 15:29 I think he could have argued as follows: Instead of the increase in vertical component of velocity, he could have said that there is a decrease in horizontal component of velocity. Then too, the ray would have bent towards the normal and the speed of light would have decreased as expected(keeping all else unchanged). Moreover, the reason for decrease in horizontal component could be possibly considered to be "friction", as water is denser(well, I don't think newton really distinguished optical density from matter density; correct me if I am wrong) So far, I think this explanation could have managed to survive for some time at least...
I'm confused about the relationship between the frequency of an electromagnetic wave and the index of refraction between air and water. At about 24:13, we see that lower frequency waves have a slower speed through a dielectric and a higher index of refraction than higher frequency waves. In particular, we see that waves with 10 to the 8th Hz frequency have a K of 78 in water and an n of 8.8. Visible light has a higher frequency (5 times 10 to the 14th) and a lower n, 1.33. Later, though, we learn that blue light has a higher n than red light. Blue light has a higher frequency than red light. How can blue light have a higher n than red light, and radio waves also have a higher n than red light? Seems inconsistent. What am I confusing?
In the optical part of the spectrum the index of refraction (water and glass) are higher for blue light than fir red. Blue has a higher freq than red. Thus the speed of light in water is lower for blue light than for red light; this is some kind of an anomaly. Use google to see how speed of light varies at different frequencies. It's also discussed on Bekefi and Barrett which is the book I use for 8.03. Electromagnetic Vibrations, Waves and Radiation by Bekefi and Barrett. The MIT Press ISBN 0-262-52047-8
I had the same mind blowing question!! How can n(blue)>n(red)?? This implies that k(blue)>k(red)... but as we know the frequency of blue light is higher than red light so it should have been that n(blue)
I have lived in the Netherlands for 20 years now (coming from Denmark) and I still have problems when buying onions (-: I am able to pronounce Van Goch though.
Thanks sir your lectures are blessings for me i am 16 year old from india and i am going to use these physics principals to solve global problems your lectures are really amazing that i became better self Lots of love sir 😊❤️
So the fact that when you pause the video or watch carefully, you can see the colours. I think that is because of the shutter speed of the camera. In a one frame (24fps of 30fps footage) duration ,the disk does not rotate a full revolution, that's why we see colours but a bit faded. If in one frame duration the disk could rotate a full revolution, then we might have seen pure white light. So my assumption is, if the footage was rolling at 30fps, then the disk have to rotate 30 rps(revolution per second) to be seen white to the RUclips viewers. Correct me if I am wrong sir.
Good day, sir. I do enjoy your lectures and those help me a lot to visualise Physics with the reality. The thing is I have a problem. I do enjoy Physics and Physic classes, but I start to feel anxious whenever I have to solve the questions with mathematics, even though I practise maths properly. How can I improve it, sir? Thanks in advance!
You have 2 options option 1: eat yogurt every day but *never on Fridays* option 2: 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. *I guarantee you that you will then do very well on the Physics portion of any freshman college or JEE exam* You will find all information you need on this channel in three playlists "Homework, Exam, Solutions & Lecture Notes". 8.01 & 8.02 will each take about 200 hours, 8.03 about 250 hours.
Thank you for this wonderful courses, Mr. Lewin! I can never truly express my entire gratitude for your efforts. I do however have a question. At around 25 minutes into this lecture, you mention that, in case the sound waves would behave as EM waves (lower frequencies have a lower refractive index, thus a higher velocity), the sound coming from a violin during a concert would come first, then would come the sound of a bass per se. Isn't it supposed to be the other way around, given that the violin has a higher sound frequency? (By the way, I became very excited when I found out that the university into which I've been accepted is the one you've graduated from :) )
Liaten carefully to what I said: "if the high freq sound traveled faster than low freq as an example". In other words I did not make a direct connection with EM waves. What I said is fine.
15:21 didn't get that sir. sine of an angle is the speed of that light ray? i mean V1/V2 ,and how can V1/V2 be the same as the sine of both angles? it confuses meeeeee
Shouldn't that blue light be faster than red light because K for blue light is smaller than K for red light?(because velocity of EM wave is inversely proportional to the square root of K and if K is decreasing with increase in frequency, K(blue)
speed of all EM waves (incuding light) in vacuum is c. in material with index of refraction n, the speed ic c/n. The difference in n for blue light vs red is an anomaly as discussed by Bekefi and Barrett.
at 46:25, you say that this picture is the one taken through the red filter but at 45:46, you say that this one was taken through red filter.........SO WHICH ONE IS ACTUALLY TAKEN THROUGH RED FILTER?
It does not show nearly as ell on video asa it did for people in my audience. If you are confused about which slide is which watch this video ruclips.net/video/M1t0egTZY44/видео.html
I MENTION THAT!!! Listen to what I say. I did mention it. Besides it's not important as all that matters is the end result and that does not show well on video.
Respected Sir, could you please explain the reason for why light slows down on entering an optically dense medium. Also, does light refract when it enters from one medium to another perpendicular (parallel to the normal).
the short answer is that the speed of light in a medium with index of refraction n is c/n. Thus it slows down in going from air to water. Why does light slow down when it enters matter? There are many ways to answer the question, and many ways to look at it, including “it just does - that’s the nature we have”. One easy way to actually answer it is to examine how Maxwell’s Equations, which interrelate space, time, electric fields, magnetic fields, charge, and how the two fields affect the matter in which they exist. The speed of light in vacuum, c, does not appear in Maxwell’s equations, but when you derive the electromagnetic wave equations by cleverly combining several of the field equations, something almost magical appears seemingly out of nowhere: a wave velocity equal to 1/Sqrt(µ0 ε0) where ε0 is the constant in Coulomb’s force law for electric fields from charges and µ0 is the corresponding constant for the magnetic force law - and this velocity 1/Sqrt(µ0 ε0) turns out to be exactly c! [In modern times the speed of light in vacuum isn’t measured experimentally anymore - it has been made a definition, and experiments are now done to measure the length of the meter based on the defined speed of light and the measured second, but historically what I said in the previous paragraph applied usefully at the time all this was done.] In matter, the electric and magnetic polarization of the matter by the fields requires replacing µ0 by µ and ε0 by ε, where is always the case that µ >= µ0 and ε >= ε0. These two measured properties of the matter describe how its polarization by the electric and magnetic fields weakens the strength of the electric and magnetic force laws inside the matter. Now here’s the important point, and the answer to your question: the speed of light in the matter now becomes 1/Sqrt(µ ε)
Hi professor Lewin, In your lecture, you said that if somebody increases the frequency, they will decrease the dielectric coefficient and therefore they will increase the speed. But then later you wrote down that blue light travels slower than red light in water, even though blue light has a higher frequency. Is this just an exception, or am I totally misunderstanding it? Thanks
If someone wants to go to MIT then are marks important or extra activities or both ? I am from India. Sir what are your tips for someone who wants to go to MIT?
I just had a very brief question about the benham top. Why do would see the colors switching position when we reverse the direction of rotation? Isn't the rate at which a particular spot on the top the same whether we rotate it clockwise or counterclockwise and therefore we should see the same color regardless of direction?
It's a good question. It has nothing to do with physics. Seeing colors is due to the way our brains are wired and the reversal of colors too. Try google
Sir I have watched your videos on interference and diffraction but still I am not able to differentiate between these two and specially in case of slits.So can you please help me in understanding these concepts
Single slit diffraction and double slit interference are BOTH interference and also BOTH diffraction. For historical reasons one is call "diffraction", the other "interference". But the bottom line is that the physics is the same ; it's due to Huygens wavelets that interfere with each other.
Sir, lots of love and respect from Assam, India. I am a student of class XII. I have a question. If an object is moving with a speed v then its mass will also increase a little (though negligibly). Which will add up to a new kinetic energy. Since E=mc^2 therefore its mass will again increase and this process will continue. Is this depicting inertia of motion?
@@lecturesbywalterlewin.they9259 Thanks for replying sir. But I don't know what gamma is. I will certainly try to learn these things. Thanks again sir.
Can someone please explain to me why when you look at a IOR table there's an index of refraction for materials like metal or stone or concrete? Light doesn't travel through stone... so wtf?
Their problem with the professors lectures are the frame rate at which the cameras are recording at they just really don't do justice to his demonstrations. Being there in person is far better.
Hello Sir, I was a bit puzzled when I saw blue light with higher index of refraction than red. Blue has higher frequency, implying lower K (dielectric constant), shouldn't this mean lower index of refraction? Am I missing something? Thank you.
Hello pro you are amazing i don't know how can i explain it but you are one of our planet precious gifts God bless you . I was wondering if you could give me some guidance or suggestions how can i can be one of those lucky students at MIT I want to learn by teachers LIKE you. Have a great day
@@lecturesbywalterlewin.they9259 Is there any chance i can get scholarship at there? I'm from Ethiopia ,preparing for national examination, university entrance examination. If it is your Will I need your help I mean we can talk if I get your email
Well, if I may be picky, you don't have 100% total reflection. You forgot to mention the evanescent waves, but this is just a PCF specialist talking here. *ps:* a part about supercontinuum generation is clearly missing here (it is MIT after all....)! It was quite new when these lessons took place, it would have been super interesting to introduce them to it! Would have been amazing for them to be introduced to the marvel of optical fibers with a FULL lesson about it!
Thanks for the eye opening lectures on physics - with all my humble opinion - i would be very glad to see - now that all physics basic university courses video are in place. A published book series of the "lecture on physics - by Walter Levin".
the index of refraction for light is an anomaly as discussed, and explained, in 8.03 Electromagnetic Vibrations, Waves and Radiation by Bekefi and Barrett. The MIT Press ISBN 0-262-52047-8
HELLO PROFESSOR LEWIN, I HAVE A GREAT HOBBY OF MAKING DIFFERENT GADGETS BASED UPON PHYSICS. RECENTLY ONLY I HAVE CREATED A WAVE PENDULUM AND IT ALSO WORKED PROPERLY. BUT SIR NOW I WANT SOME IDEAS FROM YOU TO CREATE A PROJECT BASED ON OPTICS. SO SIR PLEASE HELP ME BY SHARING YOUR PRECIOUS KNOWLEDGE......PLEASE SIR...
I don’t know how it’s done, but that sound of a dotted line when he is working with chalk is cool. If I wasn’t watching I’d swear it’s exactly the same sound the A-10 Warthog makes when it’s firing it’s 30 mm gun. Brrrraaaaa
IM A STUDENT OF CLASS 10TH CBSC ONCE MY SCIENCE TEACHER TOLD ME TO STUDY THINGS DEEPLY I THEN FOUND YOUR CHANNEL AND YOU ARE THE BEST TEACHER SIR LOVE FROM INDIA
FYI was made experiments with measuring EM waves speed of different frequency and result very interesting, close to low frequency (few kHz) speed very low (significantly slower then speed of light) it will be very interesting to repeat this experiment and explain mechanism why this happens but that mean that speed of light is not constant at all (even red and violet waves must have significant and measurable difference of speed) and with waves of higher frequency it can be more than c
Hi Mr. Lewin, WHY exactly does light refract? I just find it odd how light will slow down and change angle as it enters a medium then SPEED BACK UP without a force acting on it and change angle again when exiting, almost as if light has a natural tendency to go at c m/s. It’s so perplexing. How is this even happening at the atomic level?
@@lecturesbywalterlewin.they9259 thanks for replying. I guess it makes sense why it slows down, but do you know the real reason why it speeds up when exiting a medium with a higher index of refraction? It’s not like there’s a force acting on it, right?
I wanted to ask the following. When we turn on a torchlight we are producing electromagnetic waves. So are these a result of accelerating charges? Put differently is accelerating charges the only way to produce electromagnetic waves ? Or is there any other way to produce them ?
sir, why the refractive index of red light is less than blue light, as we know that frequency of red light is less than blue light hence dielectric coefficient (K) will be more so refractive index should be more but in this case it's not, Why?
@@lecturesbywalterlewin.they9259 ok thank you sir ..... And that previous doubt regarding generation of E waves due to accelerated charges is now cleared.👍
Hi Sir, Do you know why the "triangle of the primary colours" is not exactly a TRIANGLE in your slides? I mean, they are curved! Has this any explanation? How do they affect the proportions when you try to find a colour rate by mixing them?
If you Google Video-Swimming-pool-illusion-shows-body-separated-mans-body you will see that Snel's Law is, apparently, a matter of perspective, and not a hard physical law. This does not apply to total internal reflection. I think. edit: maybe the light leaves, say, the water, at the same angle as the beam, but, through whatever optical deformations due to different media, it looks as if it is diffracted in the air when seen from a certain angle.
Sir , why index of refraction of water for blue light is higher than that for red light ? In your lecture notes , i found that index of refraction decreases as frequency increases and blue light has a higher frequency than red light .
@@lecturesbywalterlewin.they9259 i can not find an answer on google , all what i found is articles talking about snell's law .please refere to any page .
Sir...as you said if all the VIBGYOR colors rotate at a high speed then due to persistence of vision it appears white.TRUE.But does that mean that something in the light bulb or any white source of light keeps rotating so that it appears white??
Dr.lewin I anish kumar from india.i hopefully again and again request to mention your books name that you have written,because i have to buy these. I eagrily wish thse for my......
This is the 2nd time that I sent them to you Accretion-driven Stellar X-ray sources Edited by Walter H.G. Lewin and Edward P.J. van den Heuvel Cambridge University Press, 1983 ISBN 0 521 24521 4 X-Ray Binaries Edited by Walter H.G. Lewin, Jan van Paradijs & Edward P.J. van den Heuvel Cambridge University Press, 1955 ISBN 0 521 41684 1 hardback ISBN 0 521 59934 2 paperback Compact Stellar X-Ray Sources Edited by Walter H.G. Lewin and Michiel van der Klis Cambridge University Press, 2006 ISBN 978-0-521-82659-4 Hardback ISBN 978-0-521-15806-0 Paperback For The Love of Physics by Walter Lewin with Warren Goldstein Simon & Schuster, 2011 ISBN 978-1-4391-0827-7 hardback ISBN 978-1-4516-0713-0 paperback ISBN 978-1-4391-2354-6 ebook
21:45 Doesn't this, at least in principle, allow for a diamagnetic material with Km less than 1, in which the speed of light is faster than the speed of light in vacuum?
(25:00) electro-magnetic waves with higher frequencies have a lower K, so they travel faster in water. Why then the blue light is slower in water than the red light?
It's easy for Arabian people to pronounce "Huygens" becuase the Letter "خ" in our language is pronounced "khh" so maybe it's easy for me to understand this principle
yes, the "g" in Huygens is also no problem for people who speak Hebrew. How about the "uy". Does NOT exist in English. Like in the Dutch words "thuis", "duim", "uit", "luid", "ruim, "vuil", "muil", "druif", . . . . .
If the frequency is higher, then the kappa will be lower and meanwhile the index of refraction will go down. But obviously the frequency of red light is lower than the blue one. How can the index of refraction of blue light higher than the red one?
This website contains all my 94 course lectures (8.01, 8.02 and 8.03) with improved resolution. They also include all my homework problem sets, my exams and the solutions. Also included are lecture notes and 143 short videos in which I discuss basic problems.
ENJOY!
wow, lucky students.😀😘
i want all of them downloaded what should i do?
finally love you and your lecture. unfortunately i will never get chance to meet you. i wish ................
may be in next life.
Which website?
Sir I have addiction..... It has been very difficult for me to sleep without watching your lectures for last many days.... 😊
I am sorry for that - but the good news is that you will get very smart
@@lecturesbywalterlewin.they9259 🙏🙏🙏
@@lecturesbywalterlewin.they9259
Sir can you please do something good for Indian viewers. Can all these lectures be translated into an hindi audio voice?
@@lecturesbywalterlewin.they9259 hahaha
And this addiction is good for your mind but may be not for your health, if you are too addicted..
This is the first time in my life I've heard a native Dutch speaker pronounce "Huygens." Thank you so much.
i did my best, i still cant pronounce Huygens, looks like you have to be a dutch to pronounce it properly
28:47 i'm stunned, how amazing this lectures are, this lectures make you see the world so differently
Your lectures are always amazing!
:)
MIT students were so fortunate to have Prof Lewin as their teacher. What an awesome and brilliant teacher he is.
48:14
Walter lewin: something bizarre is happening in ur brain
me: is that a jojo reference?
Light is a complicated subject which is interesting to unfold with the help of such a great lectures. Thank you Professor!
Glad it was helpful!
What's the secret behind eatable things(cup of coffee/tea sometimes banana) on Professor's shirt?????
u didnt see wht he taught but seeing other than physics
I have been also thinking about it hahahaha
What a mystery
am I the only one did not see any colour in the benham disc?
at 41:57 you can see it
I see no colours either.
@@D3tyHuff 42:20 Look at the stripes.
@@ramilhuseynov2891 That means you must be colourblind (I am too)
i think that is because of the filming is an digital signal, it has filming frency, so the signal has lost many stimulations received by your brain than the reality of native continueous signals.
Thanks a lot Professor, these notes were extremely helpful.
Glad to hear that
I have a question regarding Newton's Explanation.
15:29
I think he could have argued as follows:
Instead of the increase in vertical component of velocity, he could have said that there is a decrease in horizontal component of velocity. Then too, the ray would have bent towards the normal and the speed of light would have decreased as expected(keeping all else unchanged). Moreover, the reason for decrease in horizontal component could be possibly considered to be "friction", as water is denser(well, I don't think newton really distinguished optical density from matter density; correct me if I am wrong)
So far, I think this explanation could have managed to survive for some time at least...
I'm confused about the relationship between the frequency of an electromagnetic wave and the index of refraction between air and water. At about 24:13, we see that lower frequency waves have a slower speed through a dielectric and a higher index of refraction than higher frequency waves. In particular, we see that waves with 10 to the 8th Hz frequency have a K of 78 in water and an n of 8.8. Visible light has a higher frequency (5 times 10 to the 14th) and a lower n, 1.33. Later, though, we learn that blue light has a higher n than red light. Blue light has a higher frequency than red light. How can blue light have a higher n than red light, and radio waves also have a higher n than red light? Seems inconsistent. What am I confusing?
In the optical part of the spectrum the index of refraction (water and glass) are higher for blue light than fir red. Blue has a higher freq than red. Thus the speed of light in water is lower for blue light than for red light; this is some kind of an anomaly. Use google to see how speed of light varies at different frequencies. It's also discussed on Bekefi and Barrett which is the book I use for 8.03.
Electromagnetic Vibrations, Waves and Radiation
by Bekefi and Barrett.
The MIT Press
ISBN 0-262-52047-8
same problem for me...
that is correct. The speed of light will change, but NOT the frequency of the light.
I had the same mind blowing question!! How can n(blue)>n(red)?? This implies that k(blue)>k(red)... but as we know the frequency of blue light is higher than red light so it should have been that n(blue)
I have lived in the Netherlands for 20 years now (coming from Denmark) and I still have problems when buying onions (-:
I am able to pronounce Van Goch though.
Thanks sir your lectures are blessings for me i am 16 year old from india and i am going to use these physics principals to solve global problems your lectures are really amazing that i became better self
Lots of love sir 😊❤️
The day when I heard about you from Alakh Pandey sir I decided to study optics from you but now I have realised that my decision was not wrong
So the fact that when you pause the video or watch carefully, you can see the colours. I think that is because of the shutter speed of the camera. In a one frame (24fps of 30fps footage) duration ,the disk does not rotate a full revolution, that's why we see colours but a bit faded.
If in one frame duration the disk could rotate a full revolution, then we might have seen pure white light. So my assumption is, if the footage was rolling at 30fps, then the disk have to rotate 30 rps(revolution per second) to be seen white to the RUclips viewers. Correct me if I am wrong sir.
Respect for Sir Walter Lewin from Pakistan 🎉🎉🎉
Sir all these demonstration and excellent explanation for FREE .
You are a legendary professor 🙏🙏🙏🙏. Hats off
So nice of you
Good day, sir. I do enjoy your lectures and those help me a lot to visualise Physics with the reality. The thing is I have a problem. I do enjoy Physics and Physic classes, but I start to feel anxious whenever I have to solve the questions with mathematics, even though I practise maths properly. How can I improve it, sir?
Thanks in advance!
You have 2 options
option 1: eat yogurt every day but *never on Fridays*
option 2: 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. *I guarantee you that you will then do very well on the Physics portion of any freshman college or JEE exam* You will find all information you need on this channel in three playlists "Homework, Exam, Solutions & Lecture Notes".
8.01 & 8.02 will each take about 200 hours, 8.03 about 250 hours.
@@lecturesbywalterlewin.they9259 Thank you so much for your reply, sir. I appreciate your efforts and kindness.
@@lecturesbywalterlewin.they9259 I don't eat yogurt everyday.
Thank you for this wonderful courses, Mr. Lewin! I can never truly express my entire gratitude for your efforts.
I do however have a question. At around 25 minutes into this lecture, you mention that, in case the sound waves would behave as EM waves (lower frequencies have a lower refractive index, thus a higher velocity), the sound coming from a violin during a concert would come first, then would come the sound of a bass per se. Isn't it supposed to be the other way around, given that the violin has a higher sound frequency?
(By the way, I became very excited when I found out that the university into which I've been accepted is the one you've graduated from :) )
Liaten carefully to what I said: "if the high freq sound traveled faster than low freq as an example". In other words I did not make a direct connection with EM waves. What I said is fine.
15:21 didn't get that sir. sine of an angle is the speed of that light ray? i mean V1/V2 ,and how can V1/V2 be the same as the sine of both angles? it confuses meeeeee
google "Snell's Law"
You make me able to love physics
I am very thankful to you Sir.
Love from India 🇮🇳
I'm glad nobody was around for me trying to say Huygen
Shouldn't that blue light be faster than red light because K for blue light is smaller than K for red light?(because velocity of EM wave is inversely proportional to the square root of K and if K is decreasing with increase in frequency, K(blue)
speed of all EM waves (incuding light) in vacuum is c. in material with index of refraction n, the speed ic c/n. The difference in n for blue light vs red is an anomaly as discussed by Bekefi and Barrett.
@@lecturesbywalterlewin.they9259 Thanks a lot for replying, sir.
I come to see various experiments here !
It's really much interesting ❤
Glad you enjoy it!
at 46:25, you say that this picture is the one taken through the red filter but at 45:46, you say that this one was taken through red filter.........SO WHICH ONE IS ACTUALLY TAKEN THROUGH RED FILTER?
Why it still seems as black and white but a bit brighter even though taken through a red filter......
It does not show nearly as ell on video asa it did for people in my audience. If you are confused about which slide is which watch this video ruclips.net/video/M1t0egTZY44/видео.html
So which one was the one taken through red filter?
I MENTION THAT!!! Listen to what I say. I did mention it. Besides it's not important as all that matters is the end result and that does not show well on video.
v=M1t0egTZY44&list=PLyQSN7X0ro22Jw18-fgmWjbGcGR_K3aUh&index=7
watch the demo also here. That may help you
Respected Sir, could you please explain the reason for why light slows down on entering an optically dense medium. Also, does light refract when it enters from one medium to another perpendicular (parallel to the normal).
the short answer is that the speed of light in a medium with index of refraction n is c/n. Thus it slows down in going from air to water.
Why does light slow down when it enters matter?
There are many ways to answer the question, and many ways to look at it, including “it just does - that’s the nature we have”.
One easy way to actually answer it is to examine how Maxwell’s Equations, which interrelate space, time, electric fields, magnetic fields, charge, and how the two fields affect the matter in which they exist.
The speed of light in vacuum, c, does not appear in Maxwell’s equations, but when you derive the electromagnetic wave equations by cleverly combining several of the field equations, something almost magical appears seemingly out of nowhere: a wave velocity equal to 1/Sqrt(µ0 ε0) where ε0 is the constant in Coulomb’s force law for electric fields from charges and µ0 is the corresponding constant for the magnetic force law - and this velocity 1/Sqrt(µ0 ε0) turns out to be exactly c!
[In modern times the speed of light in vacuum isn’t measured experimentally anymore - it has been made a definition, and experiments are now done to measure the length of the meter based on the defined speed of light and the measured second, but historically what I said in the previous paragraph applied usefully at the time all this was done.]
In matter, the electric and magnetic polarization of the matter by the fields requires replacing µ0 by µ and ε0 by ε, where is always the case that µ >= µ0 and ε >= ε0. These two measured properties of the matter describe how its polarization by the electric and magnetic fields weakens the strength of the electric and magnetic force laws inside the matter.
Now here’s the important point, and the answer to your question: the speed of light in the matter now becomes 1/Sqrt(µ ε)
@@lecturesbywalterlewin.they9259 , Respected Sir, thank you so much. I will read it to make my concept clear.
sir you told high frequency EM waves will tavel faster ..then how come blue light travels 1% slower sir?
*that is an anomaly* as discussed in the 8.03 book that I used, Bekefi & Barrett. You can also try google
@@lecturesbywalterlewin.they9259 thank you sir
Sir I try to download your lecture notes but your link is not working can you suggest me another way to download?
Why do we have to take different ratio of the color in th disc it couldn't be like circular pizza 🍕 of equal ratio?
Hi professor Lewin,
In your lecture, you said that if somebody increases the frequency, they will decrease the dielectric coefficient and therefore they will increase the speed. But then later you wrote down that blue light travels slower than red light in water, even though blue light has a higher frequency. Is this just an exception, or am I totally misunderstanding it?
Thanks
+Steven Mai Yes that is an exception.
Best explanation I think is in the first topic of Lecture 12 of 8.03x by Walter Lewin
Your lectures are the best and has helped me a lot. Thank you so much.
You are welcome!
great lecture , professor. Your way of teaching physics through practical applications is truly commendable!
Thank you , professor LEWIN . I was totally engaged IN THE LECTURE
If someone wants to go to MIT then are marks important or extra activities or both ? I am from India. Sir what are your tips for someone who wants to go to MIT?
Can you make a video on it?
read MIT's admission site
@@lecturesbywalterlewin.they9259 ok :)
I just had a very brief question about the benham top. Why do would see the colors switching position when we reverse the direction of rotation? Isn't the rate at which a particular spot on the top the same whether we rotate it clockwise or counterclockwise and therefore we should see the same color regardless of direction?
It's a good question. It has nothing to do with physics. Seeing colors is due to the way our brains are wired and the reversal of colors too. Try google
Sir I have watched your videos on interference and diffraction but still I am not able to differentiate between these two and specially in case of slits.So can you please help me in understanding these concepts
Single slit diffraction and double slit interference are BOTH interference and also BOTH diffraction. For historical reasons one is call "diffraction", the other "interference". But the bottom line is that the physics is the same ; it's due to Huygens wavelets that interfere with each other.
Thanx Sir it will help me alot.
Sir, lots of love and respect from Assam, India. I am a student of class XII. I have a question. If an object is moving with a speed v then its mass will also increase a little (though negligibly). Which will add up to a new kinetic energy. Since E=mc^2 therefore its mass will again increase and this process will continue. Is this depicting inertia of motion?
if an object is moving with speed v, its mass wil not increase, but gamma will increase. E=gamma*m*c^2
@@lecturesbywalterlewin.they9259 Thanks for replying sir. But I don't know what gamma is. I will certainly try to learn these things. Thanks again sir.
n = √(K*Km)
K is dielectric constant, is Km relative permeability?
Sir which sign conventions to follow : real as +ve or the cartesian one?
Sir I am addiction to your channel
Best physics teacher I have seen in my life
The top is so cooool ! Amazing
Can someone please explain to me why when you look at a IOR table there's an index of refraction for materials like metal or stone or concrete? Light doesn't travel through stone... so wtf?
hands down the best physics teacher the world has
Their problem with the professors lectures are the frame rate at which the cameras are recording at they just really don't do justice to his demonstrations. Being there in person is far better.
Can sin (theta 2) never equal 45 degrees? because x=0 (which can't be divided), what happens in nature?
As a matter of fact, we can also tell that total internal refraction phenomena only take place when light enters from denser medium to rarer medium
Sir how refractive index of air is 1 is it imaginary or any calculation behind it?? Pls tell 🙏🏻
From the experiment may be
Sir can you please do something good for Indian viewers. Can all these lectures be translated into an hindi audio voice?
It will be more useful for Indian Students in Neet preparation because syllabus is more practical than theorytical
I never thought optics could be that interesting 🤓
Hello Sir, I was a bit puzzled when I saw blue light with higher index of refraction than red. Blue has higher frequency, implying lower K (dielectric constant), shouldn't this mean lower index of refraction? Am I missing something? Thank you.
Good question - it's called "anominal refraction" use google.
@@lecturesbywalterlewin.they9259 Ah. I see. Thank you :)
Hello pro you are amazing i don't know how can i explain it but you are one of our planet precious gifts God bless you .
I was wondering if you could give me some guidance or suggestions how can i can be one of those lucky students at MIT I want to learn by teachers LIKE you. Have a great day
read MIT's admission site
@@lecturesbywalterlewin.they9259
Is there any chance i can get scholarship at there? I'm from Ethiopia ,preparing for national examination, university entrance examination. If it is your Will I need your help I mean we can talk if I get your email
@@mygeneration399 I have 1.4 million subscribers - 350k have asked for my email address. That's why it is *TOP SECRET*
Well, if I may be picky, you don't have 100% total reflection. You forgot to mention the evanescent waves, but this is just a PCF specialist talking here.
*ps:* a part about supercontinuum generation is clearly missing here (it is MIT after all....)! It was quite new when these lessons took place, it would have been super interesting to introduce them to it! Would have been amazing for them to be introduced to the marvel of optical fibers with a FULL lesson about it!
en.wikipedia.org/wiki/Total_internal_reflection
I was getting a bit of thanos vibes through the very end of the lecture when he talked about reality 😂
If anyone has a problem with viewing colours with the spinning top, just try increasing the speed of the video. The 1.5 speed did wonders for me :)
Can you guys see the colors at 41 when he rotates the black and white because I can't???
In 15:43 he talks about the correct Dutch pronunciation of Huygens S2 Hahaha, simply unforgetable !
These lectures are timeless. Thank you so much sir.
Thanks for the eye opening lectures on physics - with all my humble opinion - i would be very glad to see - now that all physics basic university courses video are in place. A published book series of the "lecture on physics - by Walter Levin".
Concepts of physics are taught very well in this course, but people who are weak in high school math find it tough to understand few derivations.
Sir I think " for high frequency have high refractive index " and you write " radio wave have refractive index 8.8 and for light wave 1.3 in glass"
the index of refraction for light is an anomaly as discussed, and explained, in 8.03
Electromagnetic Vibrations, Waves and Radiation
by Bekefi and Barrett.
The MIT Press
ISBN 0-262-52047-8
Sir I am a commerce student but I watch your all vidoes .I am confused on myself why I am watching your vidoes. Thank you sir your a great lecturer
HELLO PROFESSOR LEWIN,
I HAVE A GREAT HOBBY OF MAKING DIFFERENT GADGETS BASED UPON PHYSICS. RECENTLY ONLY I HAVE CREATED A WAVE PENDULUM AND IT ALSO WORKED PROPERLY. BUT SIR NOW I WANT SOME IDEAS FROM YOU TO CREATE A PROJECT BASED ON OPTICS. SO SIR PLEASE HELP ME BY SHARING YOUR PRECIOUS KNOWLEDGE......PLEASE SIR...
i am from india i want to pray to god please you can survive 200 yers more ❤
If you really want to see the color maximise your brightness and speed to 1.25 the you will observe the phenomenon of benhem disc
these lectures should be translated to many languages
Your lecture are amazing sir
I don’t know how it’s done, but that sound of a dotted line when he is working with chalk is cool. If I wasn’t watching I’d swear it’s exactly the same sound the A-10 Warthog makes when it’s firing it’s 30 mm gun. Brrrraaaaa
IM A STUDENT OF CLASS 10TH CBSC ONCE MY SCIENCE TEACHER TOLD ME TO STUDY THINGS DEEPLY I THEN FOUND YOUR CHANNEL AND YOU ARE THE BEST TEACHER SIR LOVE FROM INDIA
FYI
was made experiments with measuring EM waves speed of different frequency and result very interesting,
close to low frequency (few kHz) speed very low (significantly slower then speed of light)
it will be very interesting to repeat this experiment and explain mechanism why this happens
but that mean that speed of light is not constant at all (even red and violet waves must have significant and measurable difference of speed) and with waves of higher frequency it can be more than c
Lewin Sir! Blue light has higher frequency than Red Light then refractive index of blue should be smaller ! then why it is larger?
good question. It's an anomaly - explaned in the book I use for 8.03 (Bekefi & Barret)
@@lecturesbywalterlewin.they9259 i have that book ! I will read that ( got by luck 🌜)
This is the first time in my life I've heard a native Dutch speaker pronounce "Huygens." Thank you so much.
29:49 Explanation went straight to the ❤️
Hi Mr. Lewin,
WHY exactly does light refract? I just find it odd how light will slow down and change angle as it enters a medium then SPEED BACK UP without a force acting on it and change angle again when exiting, almost as if light has a natural tendency to go at c m/s.
It’s so perplexing. How is this even happening at the atomic level?
bcoz of change of speed of light in changing media.
@@lecturesbywalterlewin.they9259 thanks for replying. I guess it makes sense why it slows down, but do you know the real reason why it speeds up when exiting a medium with a higher index of refraction? It’s not like there’s a force acting on it, right?
I wanted to ask the following. When we turn on a torchlight we are producing electromagnetic waves. So are these a result of accelerating charges? Put differently is accelerating charges the only way to produce electromagnetic waves ? Or is there any other way to produce them ?
It depends on the kind of flashlight. Google "incandescent" light, fluorescent light and LED
Germans could say Huygens too, but nobody does.
I'm going to change it, if you want :D
Am I only one who is watching his lecture in 2023
sir, why the refractive index of red light is less than blue light, as we know that frequency of red light is less than blue light hence dielectric coefficient (K) will be more so refractive index should be more but in this case it's not, Why?
this is an anomaly as discussed in Bekefi and Barrett my 8.03 book
@@lecturesbywalterlewin.they9259 ok thank you sir ..... And that previous doubt regarding generation of E waves due to accelerated charges is now cleared.👍
Hi Sir, Do you know why the "triangle of the primary colours" is not exactly a TRIANGLE in your slides? I mean, they are curved! Has this any explanation? How do they affect the proportions when you try to find a colour rate by mixing them?
use google
Prof Walter Lewin's lectures are very good, it can make you understand the concept in physics
If you Google Video-Swimming-pool-illusion-shows-body-separated-mans-body you will see that Snel's Law is, apparently, a matter of perspective, and not a hard physical law.
This does not apply to total internal reflection. I think.
edit: maybe the light leaves, say, the water, at the same angle as the beam, but, through whatever optical deformations due to different media, it looks as if it is diffracted in the air when seen from a certain angle.
What is the constant in u(mu) sin theta = constant and from where it is derived
And thanks sir for these amazing lectures
Sir what is the maximum and minimum size of water molecule that can refract the sunlight
Sir , why index of refraction of water for blue light is higher than that for red light ?
In your lecture notes , i found that index of refraction decreases as frequency increases and blue light has a higher frequency than red light .
it's an anomaly - google it
@@lecturesbywalterlewin.they9259 i can not find an answer on google , all what i found is articles talking about snell's law .please refere to any page .
Thank you very much prof l learn all the time from lectures
I have suggestion you can explain quantum machines
What was the reason behind last demonstration ?
the brain think the environment is full of red lights, and make a adjustment to the colors it feels it should be in the sunlights.
I don’t see colors in the spinning disk demonstration.
Sir...as you said if all the VIBGYOR colors rotate at a high speed then due to persistence of vision it appears white.TRUE.But does that mean that something in the light bulb or any white source of light keeps rotating so that it appears white??
no that's not the case
google "blackbody radiation"
Dr.lewin
I anish kumar from india.i hopefully again and again request to mention your books name that you have written,because i have to buy these. I eagrily wish thse for my......
This is the 2nd time that I sent them to you
Accretion-driven Stellar X-ray sources
Edited by Walter H.G. Lewin and Edward P.J. van den Heuvel
Cambridge University Press, 1983
ISBN 0 521 24521 4
X-Ray Binaries
Edited by Walter H.G. Lewin, Jan van Paradijs & Edward P.J. van den Heuvel
Cambridge University Press, 1955
ISBN 0 521 41684 1 hardback
ISBN 0 521 59934 2 paperback
Compact Stellar X-Ray Sources
Edited by Walter H.G. Lewin and Michiel van der Klis
Cambridge University Press, 2006
ISBN 978-0-521-82659-4 Hardback
ISBN 978-0-521-15806-0 Paperback
For The Love of Physics
by Walter Lewin with Warren Goldstein
Simon & Schuster, 2011
ISBN 978-1-4391-0827-7 hardback
ISBN 978-1-4516-0713-0 paperback
ISBN 978-1-4391-2354-6 ebook
21:45
Doesn't this, at least in principle, allow for a diamagnetic material with Km less than 1, in which the speed of light is faster than the speed of light in vacuum?
incorrect
@@lecturesbywalterlewin.they9259 Because Kappa will always be larger?
(25:00) electro-magnetic waves with higher frequencies have a lower K, so they travel faster in water. Why then the blue light is slower in water than the red light?
good question. It is an anomaly - discussed in Bekefi and Barrett which I used for my 8.03 lectures.
@@lecturesbywalterlewin.they9259 Thanks a lot Walter. :)
sir compare the speed of SOUND in water and air
use google
It's easy for Arabian people to pronounce "Huygens"
becuase the Letter "خ" in our language is pronounced "khh"
so maybe it's easy for me to understand this principle
yes, the "g" in Huygens is also no problem for people who speak Hebrew. How about the "uy". Does NOT exist in English. Like in the Dutch words "thuis", "duim", "uit", "luid", "ruim, "vuil", "muil", "druif", . . . . .
If the frequency is higher, then the kappa will be lower and meanwhile the index of refraction will go down. But obviously the frequency of red light is lower than the blue one. How can the index of refraction of blue light higher than the red one?
it's an anomaly, discussed in the course book I used for 8.03. use google.
Hello professor Lewin. I want to learn to pronounce Huygens correctly, as he has been my favorite scientist, second only to Fresnel...just asking...
:)
Sir should I use Rensik Halliday 'Walker' or 'Krane' for theory? PLS REPLY
Is it me or anyone else also saw colours in opposite order as reported by sir in benham top