I am a 9 year old boy in Grade 4 in Melbourne Australia. I am writing to thank you for the lecture you gave. I am a fan of maths and physics. I am learning quantum physics on my own through Wikipedia and books. My teachers saw me doing this and they didn’t want me to get bored on my maths lessons so they gave me a task to explain the mathematics of a rainbow. I was having trouble at first in finding a good video until I saw your lecture. After seeing your video, I was really excited because I fully understand this topic now and I was also blown away by how you taught and summarized so well that even a 9 year old can understand. Cannot thank you enough!!! My dream is to solve the Navier Strokes equation and win the one million dollar prize! Anbo
YESSSS if you remember the many features of a rainbow that you were NEVER aware of, you will confirm that knowledge only adds. Knowledge is the hidden beauty of the rainbow.
I never thought a mathematics lecture would bring a tear to my eye. I don't know what to say so I will say the only thing I can: thank you, Professor Lewin. God bless you.
Rainbows are beautiful, whenever i water my plants, I will try to create them and it makes me happy and admire the beauty of nature. Thankyou professor, for such brilliant lecture and book
Prof Lewin You are one of the first lecturers I have watched online, and when I watched one of your lectures, I had to watch all of them :D If only we had more teachers like you who loves what he/she is doing. Wish you the best :)
@@lecturesbywalterlewin.they9259 thank you for your presentation on SEEING a rainbow. My question for Professor Lewis, WHAT is a rainbow? There are missing links on understanding of rainbows. Thank you for sharing.
Dr. Lewin: A bonus question for a public lecture should be, "Can you ever reach the end of a rainbow?" Like the leprechaun. Can you reach that pot of gold? ;) Forgive me if somebody already thought of that question. Likely I suppose... Of course, MIT students wouldn't be stumped. Most of us know the answer. Thank you for all your wonderful MIT OpenCourseWare--over several prior decades. I am an R&D engineer in electrical and computer engineering. I love physics and electro-mechanical systems (the latter of which is waning these days). And thank you for continuing to present this knowledge via TH-cam since then--re-publishing and your constant physics challenge questions. Colorful outfits and colorful personality! I also taught university for ~16 years (many of which while working full-time in industry). I learned a lot from your teaching techniques! Much love!
As a child I saw lots of rainbow because it rained all the time in my native country!! But only now I understand HOW rainbows are formed. THANK YOU !!!Grazie mile !!
Came here to learn about a Rainbow and fell in love with this Teacher. His passion and love of Knowledge will keep me watching more of his lectures. This was so gratifying, thank you!
I had seen rainbow a few months ago and took some photographs. Now that I have learned so much about them , when I see those photos again ,I can't resist watching all the things which I have learned here. The Alexander's dark band ,the colour sequence of both the rainbows , the white light and no light area everything! It feels so good to know more. I don't want to resist seeing the things I have learned here. This lecture is amazing. I have surely fallen in love with physics of rainbow. THANK YOU VERY MUCH!
He is a wonderful lecturer. I have watched almost all his lectures. They are really useful. I have learned Physics by his lectures. Thank you professor Lewin for making Physics lovely, beautiful, and simple.
Outstanding I m greatful to Mr lewin for such a wonderful lecture that clears every doubt I have been fan of this genius professor since I watched his first lecture he never let his lecture to be boring .Every time I watch the lecture I learn something new and interesting . Thank you sir
Prof. Lewin, This rainbow lecture has 100% changed my life. I come back and watch it again from time to time. Every time I see a rainbow, I tell all that are around me all about rainbows. It has been a wonderful thing to not only observe, but to share with others, and I thank you! Sincerely, Brandon Johnson Sandusky, Ohio
Sir I am 14 years old. And I am from India. Respected sir you are teaching and way of explaining the information ℹ️ is very good 👍 . Sir this topic is in our school textbooks I can't able to understand in my school 🏫 when my teacher was teaching. But now my all concepts are cleared . Thank you sir for teaching free of cost in very easy language. Thanks sir very much. ❤
Tremendous explanations and mesmerising. This is the 4th or 5th time I have watched your lecture on rainbows Mr. Lewin. Full marks for your presentation.😀
I saw this lecture last week, since than I was waiting for rainbow to see. And finally I have seen today, 3 bows at a same time. Primary bow was so bright that I could see its full semicircular arc and one of its leg was seen as it was about 200m away from me. Felt like I can go and touch it.
Indeed it answered my question.. And now I know the reason for my confusion.. I always thought that rainbow is caused by single drop of water.. And I think prism experiment that I did during my school days was the reason to think so .. but your lecture not only cleared my doubt.. but give me insightful knowledge which will remain with me to eternity.. thank you
Although I’m already familiar with this material I so enjoy your lectures, and strongly recommend your lectures over mine any day of the week. You sir are a treasure, thank you for sharing your work.
Now, here is a teacher whom i can admire ..throughout my jounry i.e from my school to the college i have never seen a single teacher who is this much passionate about their work... i want to be an astrophysicist and i wish i get a teacher like you who make understand the fact and make me fall deeper and deeper in love with the subject ,just as like u did.. :-) a great respect to ur work sir.
After watching this past summer, I produced a complete circular rainbow about 5 ft in front of me, while watering my garden one early morning. The Sun behind me rising in the East, as I faced the West observing this complete revolutionary rainbow!! The knowledge passed on by such a brilliant mind has ignited a passion and deep desire to learn and understand the mathematical phenomenon which surrounds us. Forever I am thankful for you, Walter Lewin :)
Thank you so much for this. Any time I'm with someone and there's a rainbow, I point out all these features and get "wow!" and "I never knew!" Even some "Daddy, come look!" I'm keeping this with me till I die. Every idol I've had is gone now except you.
wow, AMAZING lecture. in calculus, we are skipping the rainbow (boo hiss) due to too many snow days. so I decided to explore on my own. i am SO GLAD I DID! now I have the disease too. thank you so much. :)
Friction basically, the chalk skips across the board and depending on pressure and grip on the chalk, that determines the length and distance between the dots.
Fantastic presentation! I will never look at another rainbow but from here forward I will clearly see them. You had this retired man on the edge of my seat for the last hour plus. K2LED
Thank you Prof Lewin. I have a degree in scientific photography, did assignments on rainbows back in the day, but even though I understood the physics, I never saw it quite like this. Fantastic.
I just had a textbook example rainbow right in front of me outside the window, even the secondary rainbow was bright and clear. Ever since I watched that lesson of yours many years ago I`m always thinking of you when I see a rainbow and hope you are well.
Profesor, estoy leyendo su libro y es maravilloso como muestra de forma clara las maravillas que nos rodean además de su sencilla y a la vez intrincada belleza.
Sir i was reading your book for the love of physics, i didn't understood the white circular rainbow, that was happening due to fog and created beautiful background rings behind the body. sometimes it is hard to imagine while reading but by this lecture video is imagination got better to understand this type of topic.
Your every lecture make me love physics. You are like a god for me now. In india in my city there is no teachers teaching physics as physics. they teach math. They are using language of equation not the hidden beauty of physics. After watching many of your lecture i have decided that i have to study physics. By the way i don't know english very well. i am trying to learn. But i can understand your lectures easily. I think may be it is because there is pure physics in your lecture not Language. Thank U very much.
hello sir lewin! I want first of all to thank you because through your lectures i am learning to see and notice the wonderful natural world around me ! that being said , allow me sir to ask you a question about light diffraction : what the condition on the width aperture that should be fulfilled in order to obtain this phenomenon?
Dear Dr. Lewin, I have to choose a background color for a rainbow project. I heard the darker background, the more visible the rainbow is. Is it true? If so, should I choose the background black? Or is there an optimal color for that? And what is the scientifistic reason of darker background makes the rainbow that is in front of it more visible?
Merve there is no such thing as one background. Watch my lecture. I explain why the sky inside of the primary bow is quite bright (white light). Why the area between the primary bow and the secondary is very dark (Alexander's Dark Band) and why the sky outside the secondary is not very dark, but nowhere nearly as bright as inside the primary. I suggest you google "rainbows" and click on "images". You will see more rainbows than you may have ever seen in your young life. You can then decide which *backgrounds* please you the most.
Professor, are these lectures creative commons? I would like to use the laser demonstration to illustrate reflection + refraction on another video explaining rainbows in portuguese. Is it possible?
I'm not sure how to word this question, I will try my best. Why is it that the primary rainbow does not have two reflections and a phi minimum instead of one reflection and phi maximum? Or, what determines the amount of reflections made in a single water droplet?
Nice teacher for a good university. I love physics and I want to enrolled to MIT, just to hear your amazing lectures. To know how to make excitement out of boring subjects. Sadly In studying on 9th
Absolutely brilliant. Thankyou. I'm puzzled by one of your comments - Is the speed of light in water 33% less than that in air or 25% less? If v in water is 0.75c, then n[water]=c/v=1.3333..
The reciprocal of "33% more" is "25% less". Percent differences aren't a simple reversal, when taking a reciprocal. They are close to a simple reversal, when it is a single digit percent change we are talking about, but not for percent changes as high as 25% and 33%. X% more is 100 - 10000/(100 + X) percent less. Since the index of refraction of water is about 1.33, the speed of light in water is 25% less.
All of your lectures really remind me of einstein explaining the theory of relativity which I saw in national geographic channel...All of your explanation are like "hey i am the inventor of physics". And With no doubt you are the Another genius of this Planet
this is amazing, ever since I was little I wondered how rainbows are so perfect, so circlular Im 13 and dont know much in physics or maths but u made it easy to understand, thank you alot!
Dear Dr. Lewin, I was outside looking at 42 degrees up from my shadow, making my friend spray water. Yet, I just saw only a little bit of specturum. So, I was wondering how does size of water drops or heat effect rainbows? How do I get a better rainbow? with a more powerful sun? with a spray that creates bigger water drops? What is the optimum way of doing it and how can I calculate it? Thank you!
Merve I have a water hose for my plants in my garden. When I choose the option of very wide beam, if there are no clouds I always see a wonderful rainbow, over an angle of at least 30 degrees. Of coz the bow is everywhere 42 degrees off the line from my head to the anti sun (which is below the horizon).
Get a glass, look at the very bottom of it, you will see light sort of refracting away. Can't see your finger thought it. Same in water, this is how to make an invisible suit by the use of refracting light, so that all in front is behind. 11:47 You could also use a strobe light effect but most people would notice that, even if they could not see you.
Sir Lewin , last night it was full moon in where I live . When I looked at the moon behind the transparent thin layer of cloud I saw a circular rainbow (moonbow) surrounding the moon. This phenomena was observed only when a thin layer of cloud was present. Unlike regular rainbows, the source of light was behind the rainbow rather than being on the opposite side. I tried to figure it out and did some research on the web but found nothing fruitful. Would you be kind enough to explain this phenomenon Sir.
@27:05 if the red light is anywhere within the 42 degree, does that mean all the colours beneath (yellow, green, blue...) consist of some element of the colour red? And the centre consist of all colour, thus resulted in white?
"white" sunlight consists of many different colors. Due to dispersion, the different colors emerge from water drops in different directions. Just like in a prism.
Dear Mr Lewin, I was also curious about that so I've done some Excel calculations and I have such maxima but they are nothing like those on the blackboard... I used Fresnel equations for calculating two transmission and one reflection coefficients... I haven't included "area density', or simply the flux of the rays... The max intensity of rainbow rays is approx 29 deg, but there are as you mentioned above many more rays for the 40 deg angle... IT works :) I have added intensities in one degree steps manually. Thanks to you, Mr Lewin :)
When you consider a drop of water and a ray of light entering at A the ray then refracted toward below in drop why does ray not refracted above from the original ray?
Lectures by Walter Lewin. They will make you ♥ Physics. Yes, professor. I understood your class, and for the first time I do understand the rainbow, and I really thank you. Im amazed. And I am using this knowledge to make a scicomm video in portuguese to explain it to brazilians! Its an entire series called “colors of the sky”! Its on the channel AstroTubers, that I create videos along with other 31 brazilian astronomers and physicists! Im really engaged. And I read your book, and more than that: I participated here on Who Wants to Be a Millionaire, that will be aired in a saturday afternoon in the biggest TV company in Brazil - the second in the world - and guess what: I spoke about your book. So maybe, september 21st I think it will be aired, your book sellings over here will have a spike. Well, about my question: you said that there is no light after 42º, ok, but, while the light interacts with the drop of water, doesnt it also scatter? Like Mie Scattering? If so, wouldnt it also go after 42º? And make a white color - however maybe even impossible to notice for 1 drop? Or maybe the scattering will also have a maximum angle and that indeed will be *no light* there. Thank you. You inspire me to be an edutainer for portuguese speakers!
Hello professor, Sometimes we see a distinctly bright circle around moon. What is it called? How is formed?Is it result of same phenomenon that causes rainbow? I see no rain drops there causing it.
Hi Prof Walter Lewin , if rainbow is formed when light is refracted by water droplets then why isn't the cloud rainbow but white instead? Looking forward for your reply please...
Good question. The water drops in clouds are very small (10-15 microns). There is no refraction as the wavelength of visible light is 0.5 micron. But there is scattering of light and diffraction. Diffraction can produce glories. I show a picture I took from my plane of a glorie in my book "For the Love of Physics. I suggest you google "glories".
@@lecturesbywalterlewin.they9259 Yes, I looked more closely. You meant Pl.: "Special Talks" But I asked to add the video in your list: " Best of Walter Lewin" . It is one of your best lecture, we both know that, Walter.
Line of sight is not a straight line, so one can see multiple angles at the the same time. Unless one specifically focuses on a point, but even then one can see multiple lines of sight. If you squint your eyes you can see less lines of sight.
Beste Walter , nogmaals bedankt voor je boek en leuke slingerfoto ....... ik heb in de tijd dat ik jou volg ,wat foto’s gemaakt van regenbogen! Ik heb er inderdaad heel veel naar gekeken, maar nog nooit een gezien 😏😏😏! Tot je optreden bij DWDD . Tevens heb ik een foto gemaakt van mij en mijn dochter mét jouw slinger foto! Zou ik jou die toe mogen sturen ??? Groeten uit Oosterhout
good morning professor. I also love physics and I always had a quest for knowledge in physics. I want to aquire a lot of knowledge in my life. I want a favor from you....
I had previledge of seeing circular rainbow. One afternoon on rainy cloudy day I happened to look upward in sky. The sun was hidden by a patch of cloud and rainbow was formed on peripheral of cloud
Knowledge only adds when you can reproduce it in reality, this way you get a sense of creating art or experimenting. So like a child you can be in awe, the first time you see something beautiful and then later knowing you can replicate it on demand is a wonderful feeling.
I KNEW WHY YOU DON'T SEE de Withe bit blue!!!i tought and tought stopping the video ,and at the end i arrived myself! I fell soo smart! p.s.sry for Any mistake
8.01 Physics Hans C. Ohanian Physics 2nd edition W.W. Norton & Company ISBN 0-393-95748-9 8.02 Physics for Scientists & Engineers by Douglas C. Giancoli. Prentice Hall Third Edition ISBN 0-13-021517-18 8.03 Vibrations and Waves by Anthony French CRC Press ISBN 9780748744473 8.03 Electromagnetic Vibrations, Waves and Radiation by Bekefi and Barrett. The MIT Press ISBN 0-262-52047-8
Hello Prof W. Lewin, Thank you for your lecture but, what about; ultra red out side the Rainbow, in the dark bend? And also inside the Rainbow with ultra violet? The Alexander dark bend has to be full with infra red, and the inside of a rainbow has to be full of ultra violet. What will we see if we look at a Rainbow with a infra red camara? Or look at it in ultra violet? I love physics, so I'll keep asking questions :-) But there is light outside the Rainbow. Greetings Jos Hoetjes Heiloo Holland
33:40 You made a line 42º to the line of sight and not to angle of incidence. This became evident on 35:15 when the lines coming out of the raindrops are not parallel. I was commenting it when 37:20 came. Walter Lewin, I love you btw.
I am a 9 year old boy in Grade 4 in Melbourne Australia. I am writing to thank you for the lecture you gave. I am a fan of maths and physics. I am learning quantum physics on my own through Wikipedia and books. My teachers saw me doing this and they didn’t want me to get bored on my maths lessons so they gave me a task to explain the mathematics of a rainbow. I was having trouble at first in finding a good video until I saw your lecture. After seeing your video, I was really excited because I fully understand this topic now and I was also blown away by how you taught and summarized so well that even a 9 year old can understand. Cannot thank you enough!!! My dream is to solve the Navier Strokes equation and win the one million dollar prize! Anbo
Thanx for your kind words
I hope you are keeping up the good work! Great job!
great job!!
can't wait to see a rainbow again to make sure that knowledge only adds, thanks for showing the hidden beauty
YESSSS if you remember the many features of a rainbow that you were NEVER aware of, you will confirm that knowledge only adds. Knowledge is the hidden beauty of the rainbow.
Sir can you explain me that when we make a rainbow by the water then why the rainbow is make like a full round path
@@mohitswami7729 because you are seeing it from the above where it can occur in 360,but if you made rainbow while laying then you will see 180
I never thought a mathematics lecture would bring a tear to my eye. I don't know what to say so I will say the only thing I can: thank you, Professor Lewin. God bless you.
Still coming back to watch it once more because I can't sleep and want to calm my mind 💫
Rainbows are beautiful, whenever i water my plants, I will try to create them and it makes me happy and admire the beauty of nature.
Thankyou professor, for such brilliant lecture and book
My pleasure 😊
Prof Lewin You are one of the first lecturers I have watched online, and when I watched one of your lectures, I had to watch all of them :D If only we had more teachers like you who loves what he/she is doing. Wish you the best :)
:)
@@lecturesbywalterlewin.they9259 thank you for your presentation on SEEING a rainbow. My question for Professor Lewis, WHAT is a rainbow?
There are missing links on understanding of rainbows.
Thank you for sharing.
Dr. Lewin:
A bonus question for a public lecture should be, "Can you ever reach the end of a rainbow?" Like the leprechaun. Can you reach that pot of gold? ;) Forgive me if somebody already thought of that question. Likely I suppose...
Of course, MIT students wouldn't be stumped.
Most of us know the answer.
Thank you for all your wonderful MIT OpenCourseWare--over several prior decades. I am an R&D engineer in electrical and computer engineering. I love physics and electro-mechanical systems (the latter of which is waning these days). And thank you for continuing to present this knowledge via TH-cam since then--re-publishing and your constant physics challenge questions. Colorful outfits and colorful personality!
I also taught university for ~16 years (many of which while working full-time in industry). I learned a lot from your teaching techniques!
Much love!
An introductory question at the beginning of the lecture of course. A question before the first 6.
As a child I saw lots of rainbow because it rained all the time in my native country!! But only now I understand HOW rainbows are formed. THANK YOU !!!Grazie mile !!
Came here to learn about a Rainbow and fell in love with this Teacher. His passion and love of Knowledge will keep me watching more of his lectures. This was so gratifying, thank you!
He really is an amazing teacher. Imagine if all teachers had the passion on their subject as he does.
Absolutely right.
Best explaination I have ever heard... Rainbow would be proud of you Sir! ❤️ Huge love and respect from India 🇮🇳
❤❤
This is pure poetry!
:)
I had seen rainbow a few months ago and took some photographs. Now that I have learned so much about them , when I see those photos again ,I can't resist watching all the things which I have learned here. The Alexander's dark band ,the colour sequence of both the rainbows , the white light and no light area everything! It feels so good to know more. I don't want to resist seeing the things I have learned here. This lecture is amazing.
I have surely fallen in love with physics of rainbow.
THANK YOU VERY MUCH!
He is a wonderful lecturer. I have watched almost all his lectures. They are really useful. I have learned Physics by his lectures. Thank you professor Lewin for making Physics lovely, beautiful, and simple.
Left speechless after being taught by such a great teacher..
🙏🏻🙏🏻
Respect and prayer for your well being sir from India..
Outstanding
I m greatful to Mr lewin for such a wonderful lecture that clears every doubt
I have been fan of this genius professor since I watched his first lecture he never let his lecture to be boring .Every time I watch the lecture I learn something new and interesting .
Thank you sir
So much of energy, dedication and power you have in this age. Thank you much for sharing knowledge !!
Prof. Lewin,
This rainbow lecture has 100% changed my life. I come back and watch it again from time to time. Every time I see a rainbow, I tell all that are around me all about rainbows. It has been a wonderful thing to not only observe, but to share with others, and I thank you!
Sincerely,
Brandon Johnson
Sandusky, Ohio
you are most welcome
Sir I am 14 years old. And I am from India. Respected sir you are teaching and way of explaining the information ℹ️ is very good 👍 . Sir this topic is in our school textbooks I can't able to understand in my school 🏫 when my teacher was teaching. But now my all concepts are cleared . Thank you sir for teaching free of cost in very easy language. Thanks sir very much. ❤
Tremendous explanations and mesmerising. This is the 4th or 5th time I have watched your lecture on rainbows Mr. Lewin. Full marks for your presentation.😀
I saw this lecture last week, since than I was waiting for rainbow to see. And finally I have seen today, 3 bows at a same time. Primary bow was so bright that I could see its full semicircular arc and one of its leg was seen as it was about 200m away from me. Felt like I can go and touch it.
What an amazing lecture! Everything is so crystal clear now in my mind.
:)
Indeed it answered my question.. And now I know the reason for my confusion.. I always thought that rainbow is caused by single drop of water.. And I think prism experiment that I did during my school days was the reason to think so .. but your lecture not only cleared my doubt.. but give me insightful knowledge which will remain with me to eternity.. thank you
Although I’m already familiar with this material I so enjoy your lectures, and strongly recommend your lectures over mine any day of the week. You sir are a treasure, thank you for sharing your work.
:)
Now, here is a teacher whom i can admire ..throughout my jounry i.e from my school to the college i have never seen a single teacher who is this much passionate about their work... i want to be an astrophysicist and i wish i get a teacher like you who make understand the fact and make me fall deeper and deeper in love with the subject ,just as like u did..
:-) a great respect to ur work sir.
After watching this past summer, I produced a complete circular rainbow about 5 ft in front of me, while watering my garden one early morning.
The Sun behind me rising in the East, as I faced the West observing this complete revolutionary rainbow!! The knowledge passed on by such a brilliant mind has ignited a passion and deep desire to learn and understand the mathematical phenomenon which surrounds us. Forever I am thankful for you, Walter Lewin :)
I am Sooo Damn Lucky that I am able to experience Professor Lewin's Lectures... and pause them and rewind them... Oh Boy! :)
Amazing class. I watch almost every year before my refraction\ prism class. Thank you so much Mr Lewin.
You are very welcome
Great Lecturer Prof Lewin.... I will expressed it this Way... The hidden beauty of your Lecturer is science.... Thank you Prof.... 👍👍
I saw two rainbows yesterday in some distance.
I related these with this lecture
Thank you so much for this. Any time I'm with someone and there's a rainbow, I point out all these features and get "wow!" and "I never knew!" Even some "Daddy, come look!" I'm keeping this with me till I die. Every idol I've had is gone now except you.
:)
wow, AMAZING lecture. in calculus, we are skipping the rainbow (boo hiss) due to too many snow days. so I decided to explore on my own. i am SO GLAD I DID! now I have the disease too. thank you so much. :)
Thank you for uploading and thank you for the epic lectures Walter Lewin. finally someone that is able to explain properly such a beautiful thing:)
Thank you Wieger
Holy shit, how does he draw those dotted lines so quickly!?!?
vibration. Holds the chalk more at the other end which results in the chalk "hopping or jumping" as unstable.
Friction basically, the chalk skips across the board and depending on pressure and grip on the chalk, that determines the length and distance between the dots.
Parkinson can help you to do that.
@@CocktaiLMolotovX professor Lewin has not got Parkinson
He's a Wizard, Harry!
This is amazing! Thank you professor for sharing your knowledge with us
:)
Fantastic presentation! I will never look at another rainbow but from here forward I will clearly see them. You had this retired man on the edge of my seat for the last hour plus. K2LED
woww spellbound. Thanks for such a beautiful lecture. You made my day.
I'm so glad!
What an outstanding performance!
:)
"Knowledge always adds, knowledge never subtracts..." ❤❤❤❤❤🌈🌈
Whatever this Lecturer has got... it's definitely contagious :D
Wow! physics is a real enjoyment.. Thanks alot from Egypt 🇪🇬👍
Thank you Prof Lewin. I have a degree in scientific photography, did assignments on rainbows back in the day, but even though I understood the physics, I never saw it quite like this. Fantastic.
Wonderful!
I just had a textbook example rainbow right in front of me outside the window, even the secondary rainbow was bright and clear. Ever since I watched that lesson of yours many years ago I`m always thinking of you when I see a rainbow and hope you are well.
Profesor, estoy leyendo su libro y es maravilloso como muestra de forma clara las maravillas que nos rodean además de su sencilla y a la vez intrincada belleza.
Estoy encantado de que te guste mi libro
Sir i was reading your book for the love of physics, i didn't understood the white circular rainbow, that was happening due to fog and created beautiful background rings behind the body. sometimes it is hard to imagine while reading but by this lecture video is imagination got better to understand this type of topic.
Thank you professor.
Your every lecture make me love physics. You are like a god for me now. In india in my city there is no teachers teaching physics as physics. they teach math. They are using language of equation not the hidden beauty of physics. After watching many of your lecture i have decided that i have to study physics.
By the way i don't know english very well. i am trying to learn. But i can understand your lectures easily. I think may be it is because there is pure physics in your lecture not Language. Thank U very much.
Hello sir... You are a genius... The simplicity with which you explain is amazing.....
:)
hello sir lewin! I want first of all to thank you because through your lectures i am learning to see and notice the wonderful natural world around me !
that being said , allow me sir to ask you a question about light diffraction : what the condition on the width aperture that should be fulfilled in order to obtain this phenomenon?
question unclear. I cover light diffraction in my 8.03 lectures
Awesome! Enjoyed it.
Dear Dr. Lewin, I have to choose a background color for a rainbow project. I heard the darker background, the more visible the rainbow is. Is it true? If so, should I choose the background black? Or is there an optimal color for that? And what is the scientifistic reason of darker background makes the rainbow that is in front of it more visible?
Merve there is no such thing as one background. Watch my lecture. I explain why the sky inside of the primary bow is quite bright (white light). Why the area between the primary bow and the secondary is very dark (Alexander's Dark Band) and why the sky outside the secondary is not very dark, but nowhere nearly as bright as inside the primary. I suggest you google "rainbows" and click on "images". You will see more rainbows than you may have ever seen in your young life. You can then decide which *backgrounds* please you the most.
Professor, are these lectures creative commons? I would like to use the laser demonstration to illustrate reflection + refraction on another video explaining rainbows in portuguese. Is it possible?
go ahead
Just saw an full rainbow. Sir you cam in my mind. ❤️❤️
:)
One don't say "the famous physicist Newton". No.
We say "Newton".
And we bow.
true
He had to say ... "The Physicist"... we should know refers to Newton. =)))
One doesn't say "the famous philosopher Plato"
We say "the philosopher"
And we bow
For sure I've never saw a rainbow before. Amazing
I'm not sure how to word this question, I will try my best.
Why is it that the primary rainbow does not have two reflections and a phi minimum instead of one reflection and phi maximum? Or, what determines the amount of reflections made in a single water droplet?
Watch my lecture. It's all explained there. You can also watch th-cam.com/video/aF6auqBCPnY/w-d-xo.html
which is a little bit more advanced.
Thanks again and again...... 😎
What if seeing rainbows from inside room or other medium⁉️ They remain all color or fews of identical since the yield value change even using windows.
OH DAMN! those are millions of diffused light cones, now I know it I already love physics and I love it more now!
This is sooo cool!! Now I know that to find the gold at the end of rainbow I only need to walk 42 degrees out of the line of my shadow!!
you got it!!!!
=) Great lecture!
@@CarlosDuarte2007 Will you please explain how is that so? I didn't understand...
amazing. thank you x
:)
Nice teacher for a good university. I love physics and I want to enrolled to MIT, just to hear your amazing lectures. To know how to make excitement out of boring subjects. Sadly In studying on 9th
:)
Absolutely brilliant. Thankyou. I'm puzzled by one of your comments - Is the speed of light in water 33% less than that in air or 25% less? If v in water is 0.75c, then n[water]=c/v=1.3333..
The reciprocal of "33% more" is "25% less". Percent differences aren't a simple reversal, when taking a reciprocal. They are close to a simple reversal, when it is a single digit percent change we are talking about, but not for percent changes as high as 25% and 33%. X% more is 100 - 10000/(100 + X) percent less.
Since the index of refraction of water is about 1.33, the speed of light in water is 25% less.
All of your lectures really remind me of einstein explaining the theory of relativity which I saw in national geographic channel...All of your explanation are like "hey i am the inventor of physics". And With no doubt you are the Another genius of this Planet
this is amazing, ever since I was little I wondered how rainbows are so perfect, so circlular
Im 13 and dont know much in physics or maths but u made it easy to understand, thank you alot!
Wonderful!
His connecting lines is always a legend for me.
Dear Dr. Lewin, I was outside looking at 42 degrees up from my shadow, making my friend spray water. Yet, I just saw only a little bit of specturum. So, I was wondering how does size of water drops or heat effect rainbows? How do I get a better rainbow? with a more powerful sun? with a spray that creates bigger water drops? What is the optimum way of doing it and how can I calculate it? Thank you!
Merve I have a water hose for my plants in my garden. When I choose the option of very wide beam, if there are no clouds I always see a wonderful rainbow, over an angle of at least 30 degrees. Of coz the bow is everywhere 42 degrees off the line from my head to the anti sun (which is below the horizon).
Thank you professor
OMG. Understood rainbow for the first time. amezing
Prof. can we see only a secondary rainbow without a primary one?
Get a glass, look at the very bottom of it, you will see light sort of refracting away. Can't see your finger thought it.
Same in water, this is how to make an invisible suit by the use of refracting light, so that all in front is behind. 11:47
You could also use a strobe light effect but most people would notice that, even if they could not see you.
Nice rainbow shirt Sir Walter :)
Hello sir I recently snapped a few picture of rainbows and I would like to share it with you. How can I do that? Thank you.
Sir Lewin , last night it was full moon in where I live . When I looked at the moon behind the transparent thin layer of cloud I saw a circular rainbow (moonbow) surrounding the moon. This phenomena was observed only when a thin layer of cloud was present. Unlike regular rainbows, the source of light was behind the rainbow rather than being on the opposite side. I tried to figure it out and did some research on the web but found nothing fruitful. Would you be kind enough to explain this phenomenon Sir.
If it wasa circle around the moon then it was probably the 22 degree halo. use google for more pictures.
@27:05 if the red light is anywhere within the 42 degree, does that mean all the colours beneath (yellow, green, blue...) consist of some element of the colour red? And the centre consist of all colour, thus resulted in white?
"white" sunlight consists of many different colors. Due to dispersion, the different colors emerge from water drops in different directions. Just like in a prism.
en.wikipedia.org/wiki/Dispersion_(optics)
Where does those Intenstity Peaks come from? (Minute 31:00). Couldn't find anything about that. :(
It's due to the geometry. Do some ray tracings it will then show up. Or even better write a program that does the ray tracing for you.
Dear Mr Lewin, I was also curious about that so I've done some Excel calculations and I have such maxima but they are nothing like those on the blackboard... I used Fresnel equations for calculating two transmission and one reflection coefficients... I haven't included "area density', or simply the flux of the rays... The max intensity of rainbow rays is approx 29 deg, but there are as you mentioned above many more rays for the 40 deg angle... IT works :) I have added intensities in one degree steps manually. Thanks to you, Mr Lewin :)
@@pawelbjanowski max intensity is at phi_max which is 42 degrees for red light. watch th-cam.com/video/iKUSWJWMSk4/w-d-xo.html
🙏🙏🙏🙏🙏⚘⚘ no words to say.
When you consider a drop of water and a ray of light entering at A the ray then refracted toward below in drop why does ray not refracted above from the original ray?
My inspiration.
Good explanation!
Thanks!
Professor, you said that would be *no light* after 42º. But what about Mie Scattering?
rainbow is not due to Mie scattering.
Lectures by Walter Lewin. They will make you ♥ Physics. Yes, professor. I understood your class, and for the first time I do understand the rainbow, and I really thank you. Im amazed. And I am using this knowledge to make a scicomm video in portuguese to explain it to brazilians! Its an entire series called “colors of the sky”! Its on the channel AstroTubers, that I create videos along with other 31 brazilian astronomers and physicists! Im really engaged. And I read your book, and more than that: I participated here on Who Wants to Be a Millionaire, that will be aired in a saturday afternoon in the biggest TV company in Brazil - the second in the world - and guess what: I spoke about your book. So maybe, september 21st I think it will be aired, your book sellings over here will have a spike. Well, about my question: you said that there is no light after 42º, ok, but, while the light interacts with the drop of water, doesnt it also scatter? Like Mie Scattering? If so, wouldnt it also go after 42º? And make a white color - however maybe even impossible to notice for 1 drop? Or maybe the scattering will also have a maximum angle and that indeed will be *no light* there. Thank you. You inspire me to be an edutainer for portuguese speakers!
:)
Hello professor,
Sometimes we see a distinctly bright circle around moon. What is it called? How is formed?Is it result of same phenomenon that causes rainbow? I see no rain drops there causing it.
google 20 degree halo
Interesting....
After that lecture I never look at the rainbow in the same way as before
Hi Prof Walter Lewin , if rainbow is formed when light is refracted by water droplets then why isn't the cloud rainbow but white instead? Looking forward for your reply please...
Good question. The water drops in clouds are very small (10-15 microns). There is no refraction as the wavelength of visible light is 0.5 micron. But there is scattering of light and diffraction. Diffraction can produce glories. I show a picture I took from my plane of a glorie in my book "For the Love of Physics. I suggest you google "glories".
Lectures by Walter Lewin. They will make you ♥ Physics. Thank you! I have searched about the glories and I understand it now! again Thank you!
:)
Walter, in this playlist I miss your video :20th century Art in the eyes of a Physicist. That is one of my favourite. Please take it into your list.
my art lecture is in the same playlist. Look more closely. It's the first video in this playlist.
@@lecturesbywalterlewin.they9259 Yes, I looked more closely. You meant Pl.: "Special Talks" But I asked to add the video in your list: " Best of Walter Lewin" . It is one of your best lecture, we both know that, Walter.
@@meikejune4009 OK will do
@@lecturesbywalterlewin.they9259 That makes me happy, because I love this lecture the most.
@@lecturesbywalterlewin.they9259 Do you remember the white rainbow? Look at them: th-cam.com/video/Idr0kwqeayE/w-d-xo.html
Line of sight is not a straight line, so one can see multiple angles at the the same time. Unless one specifically focuses on a point, but even then one can see multiple lines of sight. If you squint your eyes you can see less lines of sight.
Beste Walter , nogmaals bedankt voor je boek en leuke slingerfoto ....... ik heb in de tijd dat ik jou volg ,wat foto’s gemaakt van regenbogen! Ik heb er inderdaad heel veel naar gekeken, maar nog nooit een gezien 😏😏😏! Tot je optreden bij DWDD .
Tevens heb ik een foto gemaakt van mij en mijn dochter mét jouw slinger foto! Zou ik jou die toe mogen sturen ??? Groeten uit Oosterhout
good morning professor. I also love physics and I always had a quest for knowledge in physics. I want to aquire a lot of knowledge in my life. I want a favor from you....
+Tapendra Bc ????
I had previledge of seeing circular rainbow. One afternoon on rainy cloudy day I happened to look upward in sky. The sun was hidden by a patch of cloud and rainbow was formed on peripheral of cloud
that was not a rainbow. That was the 23 degree halo. use google
Thanks
Knowledge only adds when you can reproduce it in reality, this way you get a sense of creating art or experimenting. So like a child you can be in awe, the first time you see something beautiful and then later knowing you can replicate it on demand is a wonderful feeling.
why fi = 4r-2i
can u explain its derivation please
Too good 💖
Thanks a lot 😊
I KNEW WHY YOU DON'T SEE de Withe bit blue!!!i tought and tought stopping the video ,and at the end i arrived myself!
I fell soo smart!
p.s.sry for Any mistake
wish I meet you and have endless conversation..I mean 'conversation' from atom to universe sir!!
just bcoz for the love of physics...!!
My inspiring Lecture in my Master class.
:)
Sir why every system wants to remain in the stable form. Which mathematical expression explain it
restoring forces try to move objects to lowest possible PE. When dU/dr = 0 there is no longer any restoring force
Lectures by Walter Lewin. They will make you ♥ Physics. What is dU/dr. Sir I know that here here U is potential energy. But what this dU/dr indicates
www.hep.fsu.edu/~berg/teach/phy2048/0925.pdf
You made me fall in love with Physics sir.
8.01
Physics
Hans C. Ohanian
Physics
2nd edition
W.W. Norton & Company
ISBN 0-393-95748-9
8.02
Physics for Scientists & Engineers by Douglas C. Giancoli.
Prentice Hall
Third Edition
ISBN 0-13-021517-18
8.03
Vibrations and Waves by
Anthony French
CRC Press
ISBN 9780748744473
8.03
Electromagnetic Vibrations, Waves and Radiation
by Bekefi and Barrett.
The MIT Press
ISBN 0-262-52047-8
Hello Prof W. Lewin, Thank you for your lecture but, what about; ultra red out side the Rainbow, in the dark bend? And also inside the Rainbow with ultra violet? The Alexander dark bend has to be full with infra red, and the inside of a rainbow has to be full of ultra violet. What will we see if we look at a Rainbow with a infra red camara? Or look at it in ultra violet? I love physics, so I'll keep asking questions :-) But there is light outside the Rainbow. Greetings Jos Hoetjes Heiloo Holland
your eyes cannot see that
33:40 You made a line 42º to the line of sight and not to angle of incidence. This became evident on 35:15 when the lines coming out of the raindrops are not parallel.
I was commenting it when 37:20 came.
Walter Lewin, I love you btw.
Yes, I norticed that after this lecture. There are 3 more lectues on rainbows where I did it right - sorry
You are right. I just watched your class on 8.03 and came here for more.@@lecturesbywalterlewin.they9259