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8.02x - Lect 31 - Rainbows, Fog Bows, Haloes, Glories, Sun Dogs
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- čas přidán 15. 08. 2024
- Rainbows, Fog Bows, Supernumerary Bows, Polarization of the Bows, Haloes around the Sun and Moon, Coronae, Glories, Mock Suns (Sun Dogs). Great Demos.
Lecture Notes, 15 Questions about Rainbows: freepdfhosting....
Lecture Notes, Key Angles for the Primary Rainbow: freepdfhosting....
Assignments Lecture 29, 30 and 31: freepdfhosting....
Solutions Lecture 29, 30 and 31: freepdfhosting....
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!
What a beautiful lecture. I nearly cried when you said that we might remember you, should we see a rainbow...I hope to have that kind of lasting influence on my students someday.
I watched your lectures when I was back in high school, and had many wonderful moments with your demonstration. Now I am at college, and often feel depressed. but still your videos have been a great source of inspiration and excitement! Thanks for everything. wish you a happy new year. :)
+Shing Lau Why do you feel depressed in college?
+Lectures by Walter Lewin. They will make you ♥ Physics.
sir actually all colleges are not alike same of them make the person compel to study those subjects which we had never imagined.
@@lecturesbywalterlewin.they9259
It's now 7 years later, but having run into your question for Shing Lau here, I can't leave it unanswered... even if my answer is both an incomplete and (at least officially) an uneducated one.
Freshman year at college may very well be THE most stressful and emotionally difficult part of many young people's lives. Too often, it involves a sudden and nearly total (for many, it's the very first *ever*) separation from all family and lifetime friends: a complete disconnection from everything socially supportive that the student ever knew before that point.
Add in the often oppressive (from afar") expectations of great success (and criticism of everything else) from family: depression through unrealistic self-criticism alone isn't hard to understand in an 18-19yo alone in a completely alien environment and culture.
Thank you for this lecture.... It is amazing to discover how such everyday events of nature can be so well explained, so clearly visually presented.
Most comprehensive YET lucid explanation on rainbows and related phenomena. Thanks ! I will for sure remember this lecture all my life.
Your knowledge gave me something very special and I will be thinking of you when I'll see my next rainbow, Professor 🙏🏻
I'm so glad to learn this lecture. Today at Cambridge I exactly saw two rainbows, and this time I remembered to pay attention to the color order and rainbows' width! Thanks very much
Prof. Lewin, you gave the world of wonder to your students! One of my proudest days was when I understood Maxwells equations! 😊 Thank you for your love and great kindness!😊😊❤
From now on, every time i see a rainbow, i will check first the red is in the outer side while the blue is in the inside; i will then compare brightness of inner area with that of the outer area. And i would also try to look for the secondary rainbow. Sure, physics is fun. With all that knowledge, a rainbow is way more than just pure beauty.
I wish to sincerely thank you for the amazing lecture, Sir Walter Lewin! All the greatest greetings from Brazil!!!
Thank you so much for releasing such high quality and extremely valuable lectures for free🙏🙏. This videos have without any doubt cleared my concepts and widened my scope of physics.🤗😋❤
The most beautiful physics lecture I`ve ever seen in my life
Wowww Amazing lecture professor !!!
+InventTwig Thanks!
watching this on a rainy day
what a feeling!
amazing!
My life's changed forever. Thank you sir ! I have caught the contagious disease !
Now I see😐, whoa! Physics is even more Beautiful than I knew it before the lecture
I saw a spectacular rainbow today (perhaps the biggest and most colorful I've ever seen) and, of course, your lecture came to my mind. As well as few questions:
1. Why is the rainbow so static, given the observer moves? I walked a while as I observed it - the observation angle have changed, but the rainbow was still there of same size.
2. Why is the rainbow so static, given the drop moves? That single drop position is not fixed, it could be affected by wind, gravity etc.
3. Why is the rainbow so intense? How does that ti-i-i-i-ny beam of light, after several refractions, manages to show up as huge and intense bow, which a naked eye could recognize in a day light.
Thank you!
when you move different water drops will form your rainbow. But the radius of the bow is ALWAYS 42 degrees (to the red) and the center of the circle is always precisely opposite the sun (anti sun point). The brightness depends on the size of the water drops and on the brightness of the sky. The darker the sky the bright it will be (for you).
''This can be used as proof sooner or later.'' Nice sense of humor :)
Super cool and simple light experiment: you need a laser pointer (green works well for visibility) and bubble solution.
Simply stabilize a good size bubble or the bubble wand with a soap surface tension and shine the beam onto the surface at a very low, close-to-parallel angle and you will observe a phenomenon known as 'branched light'. The beam will 'branch' into streams inside the surface of the bubble, not dissimilar from how one of those novelty plasma ball lamps look when they operate, very aesthetically pleasing.
There are videos here on the tube about it in labs with greater controls but its extremely simple to do at home.
(I have a personal theory that a relationship exists between this and Penderson Rays but it's strictly intuitive, I don't know how the ionosphere is like a surface tension of soap but that it seems to behave very similiar albeit in a much reduced but seemingly possible relative scale of size with regards to the wavelengths and surface or layer sizes. Its just a hunch.)
39:12 Your shadow and glory on a fog bank makes for one rare and valuable photograph.
I have seen rainbow during full moon night! and there's many cloud that just circulating around the moon. but the light disperse was very faint at the edge of the clouds bcuz it refracted out at point B( which u've drawn on the blackboard). I was so lucky, have u ever wonder it?
Amazing lectures Professor Lewin! What I'm curious about is your lecture notes that you've taken to teach. I believe they're very close to your heart since you've spent immense time and effort to make them. I would love to see the notes that you make, if that's ok with you!
each of my 94 MIT course lectures are approx 30-40 pages. That's a total of about 3500 pages.. They are all stored in port folios with 3 lectures in each. Thus a total of 32 port folios which are each about 5 cm thick.
@@lecturesbywalterlewin.they9259 Amazing Prof! It is absolutely incredible that you put in 80 hours of work into each lecture. No wonder they are so amazing and popular!
Many teachers these days don't care about the subject and just teach because they have to, amd this crushes any remaining love for a subject. You have revived the fire of physics and science in me prof, and I'll be ever grateful to you for that!
@@lecturesbywalterlewin.they9259 Please if you can and would like to, share a pic or two of the carefully crafted artworks that your lecture notes are!
Marvellous lecture professor Lewin..
Arnab Mallick thank you
Yesterday I observed a rainbow on the sky which has red at the outside and blue on the inside..More interesting was the secondary with the colors reversed as you predicted..Thanks professor to help me observe that..A big kudos to you..
Arnab Mallick Arnab did you also notice that the sky indie the primary bow was brighter than outside that bow?
Ya I too observed that the sky inside the bow and nearer the blue colour was brighter and near the red was darker..completely spectacular..
Arnab Mallick The dark area between the primary and the secondary is call Alexander's Dark Band
Sir yesterday in the night time I saw a street light and observed a very elegant rainbow around it ......was that due to diffration .....light was white and weather was as if it is about to rain. A bit
11:41 red and blue light should have the same origin. The splitting occurs inside the waterdrop.
Excellent lecture 🙏🙏🙏🙏🙏🙏
Professor at 30:30 I observed that for secondary rainbow not only the colours are reversed but also the white light is now outside the rainbow, that means no matter what the darkness is after red. Is it true?
If you watched my rainbow lectures you should be able to explain all that.
@@lecturesbywalterlewin.they9259 For primary rainbow the light striking the upper half of the raindrop comes to us(after 1 reflection) and for secondary the light striking the lower half comes to us(after 2 reflections). And for angle of incidence close to 90°, throw no light at us.
Therefore the middle portion where the positioning of the rain,sun and observer is such that the angle of incidence is 90° no light comes to us
Excellent lecture. There's nothning like understanding the wonders you
have seen all your life. One thing left a bit foggy was the blue ring,
why it is blue and not white. It's because the intensity maximum of each
color is near the maximum angle, right?
correct! watch this lecture. czcams.com/video/iKUSWJWMSk4/video.html
Thank you, that verified that I did understand it. Thank you for keeping these inspiring lectures available.
thank you Saint Walter
Hello, Professor Lewin. Your lectures inspire me much to become a teacher myself and demonstrate the wonders of physics to other students! Can you tell me what kind of education you went through to get the honor of professor?
Ir degree in Physics at Univ in Delft in 1959 - then in 1965 Dr degree in Physics at the same Univ. Then a 2 yr post doctoral appointment at MIT strating in Jan 1966. In June that same year I was promoted to Assitant Prof, in 1969 I became Assoc Prof and in 1974 Full Professor. I retired in 2009.
Thank you!!!
You're welcome!
I have a question to make sure my understanding of the lecture. Throughout the video, we talked about the light that is coming out from the section c, or 3rd refraction. However, in 33:59, you mentioned circular rainbow, which cannot be shown by refraction at the point c, because the refraction at the point c supposed to go with a opposite, not totally, direction of the sun. Therefore, Can I admit that the circular rainbow is made by the light refracted period of a or b, or previous refraction from that of c?
Thank you always for sharing this wonderful lecture!
question unclear. Circular rainbows have been observed - google "circular rainbows"
I guess I wasn’t clear, so let me clarify my previous question.
As I understood, throughout the lecture, you discussed the rainbow that was generated after three times of reflection and refraction. Clearly, at 17:43, you draw the situation when the sun, human and water drops are ordered in a sun-human-water drop sequence. So that we couldn’t see the sun that is located in the rainbow.
However, at 33:59, we could see the moon located inside the rainbow. I guess the situation cannot be caused after three times of reflection and refraction. To be specific, I think the situation cannot happen in a sun-human-water drop sequence.
So is it possible that the rainbow could be generated right after the two times, not three, of the reflection and refraction with the sequence of sun-water drop- human?
@@lecturesbywalterlewin.they9259.
Professor,
Since all colors can be present where we see the blue, why do we see blue in the rainbow at all? The concept that light is dispersive makes sense to me, but this detail has always confused me. I hope this question makes sense.
James Dufour Yes your question is a very good one. I explain why you can see blue in most lectures on rainbows. Look e.g. at czcams.com/video/iKUSWJWMSk4/video.html
sir walter...the only thing I would miss is dat my daughter will not get to study under your esteemed guidance.....we in India r having Marks oriented education..but I know thatonly peoplewho have been obssesed can make somebody obssesed with something..
Not a bow man, but every time I run into an E field I can’t help thinking of you
Thank you infinitely much!
MadCodex You are very welcome!.
I don't have a polarizer with me, so I want to ask a quick question. If a polarized light like rainbow get recorded, will it still in polarized form when replayed or it will come out in unpolarized way or it will depend on the recorder or it will depend on the play-media? Appreciation to those who answered my question. Also, Dr. Lewin is the best professor and instructor I have ever seen.
If you take 2 pictures with a llinear polarizer in front of your lens - and move the polarizer 90 dgrees you will see 2 very different pictures.
Greeting Mr lewin , I have a question whose answer I'm trying to find for almost 4-5 years now, I saw a rainbow about four years ago and we'll.....I won't call it a bow so to speak. it was around 12 o clock and the sun was up high just above the head straight up , the sun whiter than usual (or at least I thought) and the sun was surrounded by two ginormous rings it was very very big I would say almost a kilometer in the sky there I saw the primary in which the colors were bright but if a remember correctly its colors were reversed that is violet on top it was thick and bright there was another faint ring on its outside it had only blue and red but the colors were in the right order that it red outside and blue inside also I did notice that that sky inside the bows was very bright (maybe that's why I thought the sun was very bright) the sky in between the bows a bit dark and the whole of the remaining sky was dark it almost seemed that it it 6 or 5 o clock in the afternoon . I found it very bizarre and it was so strange. as you pointed out in your lecture that it's not likely to see a rainbow in mid day , the same I read in other books and it confuses me. I really wish that I had a camera at that time and i couldnt photograph it. Do you know how this could have happened professor ? PS : the sky was clear
+InventTwig You have seen haloes and arcs which are formed by ice crystals in the Earth atmosphere. I suggest you google "atmospheric optics". You will see many wonderful images. Some of them you may recognize.
+Lectures by Walter Lewin. They will make you ♥ Physics. wow Thanks :))
I just have to ask.... are you really Walter Lewin?... if so.. then for the first time I feel like I'm talking to a Celebrity... THANK YOU for all you have contributed to the understanding of Physics in your remarkable Style... I started watching your Videos back in february of 2010 and I was HOOKED on your lectures..... I still go back and see them again.... THANK YOU WALTER LEWIN ...
Oh, by the way... I've had a Polarizer Sheet for years.... recently I discovered that my Computer Monitor... LCD version... is Polarized Light..... Guess I'll have to research LCD's and see WHY the light is polarized.... Thanks for the Inspiration...
+Philip Y Yes I (\\/\///////@lter Lewin) am running this site. Thank you for your kind words. LCD's are polarized. czcams.com/video/2ilIPNu1ab0/video.html
+Lectures by Walter Lewin. They will make you ♥ Physics. Thank You Dr. Lewin!!.. I watched that Video you posted on LCD polarization... I guess you were right.. PHYSICS WORKS!! ha ha...
If phi-max for red is 42.4 deg, and for blue it is 40.6 deg, why does the inner part of the rainbow (say at around 41 degrees) actually look blue? Isn't there red light there too because it's inside of 42.4 degrees? Shouldn't it go from red to maybe yellow (as you add green) but once blue gets added that should make the light white? Why is there a visible blue section?
watch this lecture 14 minutes into the lecture czcams.com/video/iKUSWJWMSk4/video.html
*41 min into the lecture not 14 min*
Can't the white light between the diffracted rays of light be diffracted by water droplets to form a rainbow in the otherwise blind zone professor?
Castor Gemini Castor, I do not understand your question. The rainbow is the result of refraction, not diffraction. If the water drops are very small, supernumerary bows are formed mostly in the blue part of the rainbow; they are the result of diffraction. I must have shown a slide of this. In extreme cases for very very small drops diffraction will become very important and the entire bow will turn white. These are called fog bows. I show one in my lectures. The radius of a fog bow is again about 42 degrees. I discuss this also in my book "For the Love of Phyics and I also show a picture of this in my book.
Sorry, professor, wrong term there, it was supposed to be dispersion, not diffraction.
What I meant was, a light ray incident on a water droplet will emerge as a cone, with red light at the circumference, and the colours till blue towards the centre, and white at the centre of the cone, as your diagram on the blackboard shows. So, if the white light in the cone is incident on another water droplet, won't that create another cone (and hence, another rainbow?)
This is a bit difficult to put in words, I wish there was some way of uploading images into comments; that might make my question easier to communicate..
Castor Gemini A rainbow is formed when light coming from MY BACK enters water drops which are in front of me. That is a necessary condition. The white light inside the bow is NOT coming from my back; it is coming towards me from the drops that are in front of me. Thus it will not form a rainbow.
Thanks Professor! That clears up one of my questions, but I still have another.
Why won't the white light inside the cone get dispersed again? Does it lose too much intensity after refraction?
Castor Gemini In principle as that white light comes to me it would disperse if it enters water drops. But I will NOT be able to see that light (see my previous msg)
One more thing, which puzzled me today. I took a photo of my LCD TV (switched off) with a flash light on. And the white light had four diagonal strokes of colored spectrum, as could be seen on this photo:
www.dropbox.com/s/fgcw2jdi3mr1de6/Rainbow.jpg?dl=0
Why did this happen? And why exactly four diagonal strokes?
Thank you!
I have no permission to view the picture
Sorry. This one should work: imgur.com/a/KeMdG
interesting pattern. It has the appearance of a diffraction pattern, but that's about all I can say.
Wonderful lecture. I was wondering - what about the refraction at point B, couldn't it also produce a rainbow?
djbanizza That is an excellent question. The light that emerges at B will indeed be dispersed. But if you do the ray tracing at various values of the angle i the colors will wash out. You could test this using a glass sphere and shine a wide beam of light on it. Then project the light that emerges on the back side of the sphere on a white screen. No rainbow! The rainbow ONLY appears near phi_max (primary) and near phi_min (secondary).
What happens if there are different refraction indexes in this situation? (for example, if we have a different gas in the atmosphere, or the drops are not water drops, or even the complete opposite situation, if we have air bubbles in water). Would we see a rainbow with the colors inversed if n1 is bigger than n2? Would we see it in different angles? Are there any practical examples for that?
work it out on your own. In lecture 22 of my 8.03 lectures I work it out for spherical glass beads.
@@lecturesbywalterlewin.they9259 Ok! Thanks for replying
Dear teacher, what is the reason for using the index of refraction of 1.336?
28:06 Who is the artist professor?
It's very lucky if the runner of this site were Dr. Lewin... The very great physics lecturer I have ever seen. By the way, I'm actually curious with the notes you used in every lecture you conducted. Perhaps you could show me some of the contents of your notes please? I believe that it would also inspire me...
+Aska Gifari Each lecture is aprox 50 pages of large handwritten notes with time marks to keep me on schedule. There are 3 lectures in one 2 inch hard cover folder. Thus there are 12 such folders for 8.01 and also for 8.02 but 8 for 8.03 (23 lectures 85 min each). These notes also contain some very personal notes about my life. I can send you a picture which will show you how I have stored all these folders at my estate in Connecticut. They are close to my heart and I sometimes consult them. They are a major part of my life. If you send me your email I will send you a picture.
That is very great and I have to thank if you don't mind to send me a picture of that notes. Here is my email: aska.al.gifari@gmail.com. But could you also, if you don't mind, send me a picture of one page of your notes content, of course not the one that contain your personal notes, please?
By the way, 50 pages for every lecture must be a hard work, for me. But I know, that will be easy if we enjoy it. How long do you prepare a note for a lecture?
To tell you the truth, I’m also a teacher. This semester, I teach vibration and waves, and I’m so lucky find your lectures on vibration and waves. I watch them and inspiring me in teaching my students. What a valuable your lecture videos. Thanks very much...
+Aska Gifari I sent you 4 pictures. * storage of all lecture notes, * light settings lect 1 8.01, * first page notes lect 1 8.01, * time mark of my goal to have 9 min left in lect 1 (notice the times "left" of my dry runs). I always do 3 dry runs of each lecture. The last dry run I do at 6 AM of the day of the lecture. Preparation for 1 lecture including demos is about 60 hours. Great that you are teaching Vibrations and Waves. 8.03 ! ! ! Perhaps I should have sent you pictures of the start of my 8.03 course.
@@lecturesbywalterlewin.they9259 Dear Professor, I'm a huge fan of your lectures and your persona. Any chance you could forward the mail to me as well (even if 6 years have gone by, I have long fantasized about seeing just one page!).
19:39, thank you so much dear Professor Lewin, is this 42 degree the same angle PHI we got behind the the water drop? To me they are not the same. PHI is behind water drop and facing the beam, while this one is facing the opposite. if the observer is farther from the water drop, would this 42 change too?
whether you are 1 m or 10 m or 100 m or 1000 m or 10,000 m from ther rain, *your bow* has a radius of about 42 degrees.
Lectures by Walter Lewin. They will make you ♥ Physics. Thank you so much dear Professor Lewin. Have a good day and stay safe!
ai thought may be there was some physiological deformity in my brain lobes that I never understood maths or sciencelije eEinstein had for reasoning...But here u r m actually loving physics sir..but the only thing thats intimidating me is that m married:-)
Interesting
I can answer 0 of the questions all 12 of the questions and any combination thereof all the time none of the time some of the time superimposed on the rainbow itself but only if I observed it firsthand
sir, you didnt mention abt how you can measure angles in the sky, are you referring to using hands to estimate altitude ? like one finger is 1 degree and your palm is 10 degree?
you measure it the SAME way you would measure an angle at your home. Fingers and hands is VERY unreliable. You will need a protector.
Saint Walter indeed.
Sir I prepared one video in this I make rainbow using small sparkle of water and I want to share with you but I can I send it to you.
Thanks for your kindness. I have already countless pictures like that. no need to send one more.
Ive seen a extremely brilliant pair of upside down rainbows from an airplane above UK. That was very impressive. I also got pictures from my father showing a faint third rainbow.
you probably saw glories not rainbows.
@@lecturesbywalterlewin.they9259
Wow, very fast answer. Thank you. Whats the difference? I know it was raining below us that day.
HUGE difference - google "glory" or "atmospheric glories"
Sir how are INVERTED BOWS formed and why are they so uncommon
en.wikipedia.org/wiki/Inverted_bow
Hi Walter, I noticed that the photo of the glory at 35:27 appears to have a secondary bow (more visible in your book) and I have seen a secondary bow on similar photos of glories (for example, here: stephenwhitt.files.wordpress.com/2011/12/glory.jpg ). To me at least, the secondary bow appears to have the same colour order as the primary bow, red through to blue, rather than in reverse order as you describe for regular rainbows. Is this really the case? If so, why does this occur? Many thanks!
glories can have many colors and the same color can sometimes be seen twice or 3 times. It all depends on the size of the drops in the fog. They are not secondaries as in the case of rainbows as the glories are not due to refraction.
Lectures by Walter Lewin. They will make you ♥ Physics. I understand now, thank you!
google "atmospheric glories" and then click on "images"
Sir, why light from point B doesn't create a rainbow??
question unclear. I cannot add to the clarity of my lecture. I explain how the 2 bows are formed . Try this lecture (also on rainbows): czcams.com/video/iKUSWJWMSk4/video.html
I think you can't see it because the vision angular is not only quite close to but also in the opposite direction of the incoming sun light which is way much lighter and over kill the rainbow.
I urgently need to buy a polarizer 😉
:)
Sir, Why can't phi be greater than 42°?
I explain that in my lecture
Mr. Snell says so...
🤣👁️👀👁️👁️