Back in the 70s i was working for a TV repair man . And as you remember television sets were analog and all had cathode ray tubes. The color TV sets used 25,000 volts created by the fly-back transformer through a tube diode into an electrode inside a rubber cap. The TV repairman held the cap in his hand while the set was on ! !. You could see lots of large electrical arcs coming out and into his hand. And he had no adverse effects.
hi,professor. I'm from Japan. I have been wanted to know why the color of sky is blue since I was a elementary school student. you answered my questions thank you. and I love your lecture.
Sir you will be immotral even after 1000 of years because whoever will see in the next generation will love your lectures.I love so much your lecture sir. You are great physicist who made 100000 of people love with physics. Thank you for your all precious lectures sir. I am also lover of physics . Everywhere I see physics that you had made me.
Great demonstration of scattering of light by smokes of cigarettes but I think it would have been better if Walter would have preferred the Indian way of glowing incense sticks before the light than blowing those harmful cigarettes.
@@lecturesbywalterlewin.they9259 Really witty full reply from you Sir. Actually I was going through your famously written book " For the love of physics". I have enjoyed everything written in it and it aroused within me a sense of wonder, a way to see the truth through the eyes of physics. But one thing that put me in worry is the experiment of scattering of light by the smokes of cigarettes. I thought cigarette smoke would have harmed you and that too holding smoke within lungs would have caused difficulties for you. So I thought of an alternative and incense sticks came to my mind. And to turn blue light to white light artificially produced smog could have been used. But Sir truly I like your daredevil demonstrations to show the beauties of physics. All your efforts are unmatchable and extraordinary. I have great love and respect for you. Right at this time your written book is on my table. Love from India Prof. Lewin.
@@lecturesbywalterlewin.they9259 I googled it. And now I know, what it is, that Generator you used. And I had a very peaceful day of 2. Advent. Because I'm total alone. And I thought, sad that I will never be able to go on Windsurfing at France at the Atlantic, because I'm to old for trying it. I did it at the Baltic Sea once. Walter, we must finish that exercises, too dangerous for us.
Hi Walter, Henny from Holland (Oosterhout ) again! Last week i spend one weekend in Luxemburg . And i saw something spectaculair , Well i think it is!!! I proceed in dutch! De zon was al achter de horizon verdwenen, en er vloog een vliegtuig over, met de witte strepen achter zich ! Maar vóór het vliegtuig , was er een donkerblauwe streep , die het vliegtuig léék te volgen! Ik heb dit nog nooit gezien! Zou dit de schaduwvorming van het vliegtuig kunnen zijn? Ps in de blauwe lucht , was dit een donkerblauwe streep, en ter hoogte van een witte wolk, was dit een lichtgrijze streep! Groeten uit Oosterhout !
I asked because I've done measurements in the past in such experimental setups that led me to conclusion it was quite difficult to charge human body by small VDG to potentials over 100 kV (even during dry days ). Usually the leakage of the charges from the body is to great for small VDG to compensate and voltage drops significantly when one loads the machine
Professor, if in Rayleigh scattering, red light is scattered the least, then I think that red light should be more abundant in our vision as it directly reaches our eyes, the sun should then, appear red, even at noon.
The sun radiates more or less like a 5760 K black body. During midday in the direction of the sun only a few percent of the light is scattered and absorbed. But when the sun is only 2 degrees above the horizon 99.9% is scattered and absorbed in the atmosphere that's why the sun is then red.
professor , it is an awesome lecture , but i have some doubts ..... 1. in the last experiment of yours , why does the colour of the sun change gradually , is it because , you are adding more and more sulphuric acid gradually. 2. why doesnt that light refract
1. the closer the sun comes to the horizon the more atmosphere is between the sun and me. In my demo the precipitation of sulfur increases in time (chemistry). 2. ofcoz there is refraction but I shine the light through the liquid at near 90 degrees.
Professor I have the question. You said that the cloud is orange when the sun is near set or rise? Is it because the the only leftover color is orange and it scatter the particle in the atmosphere and hit cloud? If so, why the cloud is not blue when the blue scatter light hit the cloud?
Professor, first of all I need to thank you for your video lectures. They help me a lot with my physics students. I'm very interested in the sunset experiment, honestly to include the drama I want to try to replicate it in my class but honestly I don't undestand very well the composition of the solution in the bucket. If you can give me please the composition and the concentration of both the bucket solution and the sulfuric acid I will be very grateful to you.
Walter I have some funny ideas with that bucket-experiment. I thought about Beckett: Waiting for Godot.. We are.all waiting. I'm lost. Should I go there or to another place.or better stay? But the experiment is nice. I want that you help me here to build that bucket Beckett experiment.
@@lecturesbywalterlewin.they9259 I saw it once in a Theater. It is a bit scary, because it isn't clear, if Estragon and Wladimir are dead or alive. I think, before Waiting for Godot we were in : Max Frisch: Biedermann und die Brandstifter. I hope you know that. Let's wait.
@@lecturesbywalterlewin.they9259 I love more this play " Mirandolina" by Carlo Goldoni. You have never heard about it, Walter Lewin, but "Mirandolina" is one of my favorite.
Sir I want to understand the phenomenon of "mirage" on roads in hot summer when it seems water on roads. please if you have link of your such lecture. share with me
this is the most common mirage - See it every year many many times. Google "mirages" and it will be explained. It's due to the temperature gradient near hot roads which courses a density gradient in air.
@@lecturesbywalterlewin.they9259sir!, I have googled it! I have understood the temperature variance as well. But I'm confused about the " topretendwater" , is it reflection of sky on roads or just reflection of water droplets in air?
I dont get one thing... if sunsets are red, why arent sunrises red too? I mean... the dust is still in the atmosphere and blocks blue (and other) light, so... why is it not red?
Lectures by Walter Lewin. They will make you ♥ Physics. Never seen a red one xD I will wake up early tomorrow and see for myself, I can record it you want, sir :D
But sir you are totally wrong from your observation I think the background is the black shadows why don't you try to change the background with other color rather than black shadows say red shadow you will get an interesting another conclusion try to experiment further
hi professor I want to ask that If read in your book for the love of physics that sky is dark at moon because there is not atmosphere but sky is also black on earth
I guess you expect it to be otherwise? For what reason? My answer below, though I’d encourage you to think about it a bit before clicking on “see more”. In short, the same scattered light that goes into our eyes is also what goes through the lens, to expose the film or digital sensor. So, if the film or digital sensor are set up to differentiate different colors of light, and the scattered light is blue, then that’s what will turn up when we process (whether chemically or electronically) the image. Right?
+Lectures by Walter Lewin. They will make you ♥ Physics. Excuse my stupid question sir, but is it false to state that the value of voltage is what allows the current to flow through human body, according to Ohm's law V=RxI? in this case, the higher value of current that can go across the body is determined by human body resistance, isn't it? therefore, lower is the voltage, lower is the current that can flow if resistance is constant. so if voltage is low, severe damages should not occur . where am I wrong?
+Lectures by Walter Lewin. They will make you ♥ Physics. this is clear to me but I believe that voltage like 12V (as it is in car batteries) even if current may be quite high, the current that flows in the body is usually low due to resistance, which may vary from point to point and which is influenced by other different elements, right?
The audience were so dumb... Just responding in laughs... No answers to the question such a great professor... When he wanted a volunteer, after 5 mins a girl came..
Back in the 70s i was working for a TV repair man . And as you remember television sets were analog and all had cathode ray tubes. The color TV sets used 25,000 volts created by the fly-back transformer through a tube diode into an electrode inside a rubber cap. The TV repairman held the cap in his hand while the set was on ! !. You could see lots of large electrical arcs coming out and into his hand. And he had no adverse effects.
I was reading the book "for the love of physics", read there about this experiment and came here to see.... its amazing....
Same here lol
Same here mate 😊!
Same here lol
Same here
1 hour well spent
As this man said:"teachers who makes physics boring are criminal"so i guess my teacher is a serial killer
Sir I am just amazed. I just hope I could have a friend like you. Love from India.
Physics enthusiast preparing for JEE and Medical Entrances.
Both?
hi,professor. I'm from Japan.
I have been wanted to know why the color of sky is blue
since I was a elementary school student.
you answered my questions thank you.
and I love your lecture.
:)
It is mind-blowing , amazing to see sunset in a lecture hall.
:)
Your so funny professor Lewin, love you!!
Wow...that's really great ❤️💞❤️💞❤️💞❤️ one of the best physicsist and also best teacher
Wow, thank you
Sir you will be immotral even after 1000 of years because whoever will see in the next generation will love your lectures.I love so much your lecture sir.
You are great physicist who made 100000 of people love with physics.
Thank you for your all precious lectures sir.
I am also lover of physics . Everywhere I see physics that you had made me.
you made me in another world ,Dr walter ❤️ thanks alot
My pleasure!
Best physics lecture ever watched.
Thank you sir
Welcome
Amazing !!!! Great physicist 👏🏻👏🏻👏🏻
sir, you are the best teacher I have ever seen. Love from India
Why these videos have so scant views and likes... it should touch millions.
Great demonstration of scattering of light by smokes of cigarettes but I think it would have been better if Walter would have preferred the Indian way of glowing incense sticks before the light than blowing those harmful cigarettes.
how do you then change the color from blue to white?
@@lecturesbywalterlewin.they9259
Really witty full reply from you Sir. Actually I was going through your famously written book " For the love of physics". I have enjoyed everything written in it and it aroused within me a sense of wonder, a way to see the truth through the eyes of physics. But one thing that put me in worry is the experiment of scattering of light by the smokes of cigarettes. I thought cigarette smoke would have harmed you and that too holding smoke within lungs would have caused difficulties for you. So I thought of an alternative and incense sticks came to my mind. And to turn blue light to white light artificially produced smog could have been used. But Sir truly I like your daredevil demonstrations to show the beauties of physics. All your efforts are unmatchable and extraordinary. I have great love and respect for you. Right at this time your written book is on my table.
Love from India Prof. Lewin.
Exemplar of real scientific education.!
The experiment with the two water buckets is very interesting. Seems to be mysterious. I will look, what you have done there.
google "Kelvin Water Dropper"
@@lecturesbywalterlewin.they9259 I googled it. And now I know, what it is, that Generator you used. And I had a very peaceful day of 2. Advent. Because I'm total alone. And I thought, sad that I will never be able to go on Windsurfing at France at the Atlantic, because I'm to old for trying it. I did it at the Baltic Sea once. Walter, we must finish that exercises, too dangerous for us.
@@lecturesbywalterlewin.they9259 You are a wonderful friend, Walter Lewin and I love you.
Hi Walter, Henny from Holland (Oosterhout ) again! Last week i spend one weekend in Luxemburg .
And i saw something spectaculair , Well i think it is!!! I proceed in dutch!
De zon was al achter de horizon verdwenen, en er vloog een vliegtuig over, met de witte strepen achter zich !
Maar vóór het vliegtuig , was er een donkerblauwe streep , die het vliegtuig léék te volgen!
Ik heb dit nog nooit gezien! Zou dit de schaduwvorming van het vliegtuig kunnen zijn?
Ps in de blauwe lucht , was dit een donkerblauwe streep, en ter hoogte van een witte wolk, was dit een lichtgrijze streep! Groeten uit Oosterhout !
dat is heel waarschijnlijk de schaduw van het vliegtuig geprojecteerd op nearby thin clouds of de schaduw van een contrail.
Hi professor Lewin!
26:25 Q: Are you positive that VDG could charge you all way up to 120 kV)?
+dxdx666 I am reasonably confident.
I asked because I've done measurements in the past in such experimental setups that led me to conclusion it was quite difficult to charge human body by small VDG to potentials over 100 kV (even during dry days ). Usually the leakage of the charges from the body is to great for small VDG to compensate and voltage drops significantly when one loads the machine
+dxdx666 I do not exclude that it was lower than 120 kV
What's the sound at 18:43
professor, what is the significance in Rutile Titanium oxide prism. as we also find titanium oxide in other forms like ilmenite, anatase etc.. ??
I have no idea. Try Google.
This Buket-Beckett is a sculpture! You are an Artist, Walter. (Meike,Third of December 2021.)
Professor, if in Rayleigh scattering, red light is scattered the least, then I think that red light should be more abundant in our vision as it directly reaches our eyes, the sun should then, appear red, even at noon.
The sun radiates more or less like a 5760 K black body. During midday in the direction of the sun only a few percent of the light is scattered and absorbed. But when the sun is only 2 degrees above the horizon 99.9% is scattered and absorbed in the atmosphere that's why the sun is then red.
Hello Professor, I am from Mongolia , Can you upload this lecture to English subtitles please. thank you.
+Zolboo Enkhjargal Most of my lectures have subtitles but not all. I cannot hang that anymore.
professor , it is an awesome lecture , but i have some doubts .....
1. in the last experiment of yours , why does the colour of the sun change gradually ,
is it because , you are adding more and more sulphuric acid gradually.
2. why doesnt that light refract
1. the closer the sun comes to the horizon the more atmosphere is between the sun and me. In my demo the precipitation of sulfur increases in time (chemistry).
2. ofcoz there is refraction but I shine the light through the liquid at near 90 degrees.
oh ok sir
Professor I have the question. You said that the cloud is orange when the sun is near set or rise? Is it because the the only leftover color is orange and it scatter the particle in the atmosphere and hit cloud? If so, why the cloud is not blue when the blue scatter light hit the cloud?
Rayleigh scattering removes a major fraction of the short wavelength of the solar spectrum.
I still don't understand. Could you explain more?@@lecturesbywalterlewin.they9259
Professor, first of all I need to thank you for your video lectures. They help me a lot with my physics students. I'm very interested in the sunset experiment, honestly to include the drama I want to try to replicate it in my class but honestly I don't undestand very well the composition of the solution in the bucket. If you can give me please the composition and the concentration of both the bucket solution and the sulfuric acid I will be very grateful to you.
contact Andy Neil at MIT. aneely@MIT.EDU
had a debate with my friend ----- does rayleigh scattering of light depends on particles or on wavelenght of light
use google -its all there
sir why doesn't yellow or green light scatter. Their wavelength is less than blue light, so scattering should be more.
wavelength blue is 450 nm
red 650 nm
blue is the shortest
violet has smallest wavelength. The why only blue is scattered
the sun has very little violet in it's septrum
also our eyes are not very sensitive to violet
hello sir ,how u concluded Sun's spectrum consists only small portion of violet .
why not sky is violet r indigo
am not satisfied with ur explanation
I would like to ask Prof . Lewin why did he use the tougue?
Sir, subtitles are disabled please inable sir🙏🏻🙏🏻🙏🏻🙏🏻
there are no subtitles - they can be added if someone sends me the cc file.
Dear Sir ,
During the sunset experiment how much quantity of hypo and sulfuric acid did you use ?
I do not remember
I SAW A WHITE SUNSET YSESTERDAY 14TH APRIL 2018
Walter must I smoke three cigarettes parallel to repeat that experiment?
1 cigaret will do. But I always add drama to my lectures.
@@lecturesbywalterlewin.they9259 You Are that Drama, you don't add it.
Walter I have some funny ideas with that bucket-experiment. I thought about Beckett: Waiting for Godot.. We are.all waiting. I'm lost. Should I go there or to another place.or better stay? But the experiment is nice. I want that you help me here to build that bucket Beckett experiment.
Waiting for Godot is one of my favorite plays.
@@lecturesbywalterlewin.they9259 I saw it once in a Theater. It is a bit scary, because it isn't clear, if Estragon and Wladimir are dead or alive. I think, before Waiting for Godot we were in : Max Frisch: Biedermann und die Brandstifter.
I hope you know that.
Let's wait.
@@lecturesbywalterlewin.they9259 I love more this play " Mirandolina" by Carlo Goldoni. You have never heard about it, Walter Lewin, but "Mirandolina" is one of my favorite.
Is ist about lightning 🌩?
Sir I want to understand the phenomenon of "mirage" on roads in hot summer when it seems water on roads.
please if you have link of your such lecture. share with me
this is the most common mirage - See it every year many many times. Google "mirages" and it will be explained. It's due to the temperature gradient near hot roads which courses a density gradient in air.
@@lecturesbywalterlewin.they9259 your highness my dear sir
@@lecturesbywalterlewin.they9259sir!, I have googled it! I have understood the temperature variance as well. But I'm confused about the " topretendwater" , is it reflection of sky on roads or just reflection of water droplets in air?
Sir can you please tell me about scattering cross section?
use google
@@lecturesbywalterlewin.they9259 I love how you answer everyone
I dont get one thing... if sunsets are red, why arent sunrises red too? I mean... the dust is still in the atmosphere and blocks blue (and other) light, so... why is it not red?
of course they are also red
Lectures by Walter Lewin. They will make you ♥ Physics. Never seen a red one xD I will wake up early tomorrow and see for myself, I can record it you want, sir :D
Thank you. What about the color of jet sprayed geoengineering materials for weather modification? GeoEngineeringWatch.org
+EurekaRecycler I suggest you ask Google
But sir you are totally wrong from your observation I think the background is the black shadows why don't you try to change the background with other color rather than black shadows say red shadow you will get an interesting another conclusion try to experiment further
sir why dispersion occur on prism and not in rectangular glass salb????
Watch my lecture czcams.com/video/irpjwXpa4xU/video.html
The lectures of physics are totally different in Nepal than yours they don't perform these experiments for us like you do.
hi professor
I want to ask that If read in your book for the love of physics that sky is dark at moon because there is not atmosphere but sky is also black on earth
at night
The blending of white light and dark shadows is blue
Why does kelvin water dropper creates high voltages?
I explane that in my 8.02 lectures, watch them
Sir, how is the sky still blue in photographic images?
I guess you expect it to be otherwise? For what reason?
My answer below, though I’d encourage you to think about it a bit before clicking on “see more”.
In short, the same scattered light that goes into our eyes is also what goes through the lens, to expose the film or digital sensor. So, if the film or digital sensor are set up to differentiate different colors of light, and the scattered light is blue, then that’s what will turn up when we process (whether chemically or electronically) the image. Right?
Sir,At 5:28 by in general do you mean ohmic resistances
I watched from 5:00-7:00 it's crystal clear ai cannot add to it.
Ok sir thanks for your reply.you re fast
Sir do you have any astronomy lecture playlist on your channel?
YOU DID THAT ON THE EARTH CANT NASA DO IT ON THE EARTH TOO
Who r those 6 dumb people who disliked this lecture?
Why is he trembling..
Medical issues,
what if we have a very high current but a very very low voltage can it kill you??!
+niki isufi Voltage is unimportant; what kills you is current.
+Lectures by Walter Lewin. They will make you ♥ Physics. Thanks Mister Lewin for the response :)
+Lectures by Walter Lewin. They will make you ♥ Physics. Excuse my stupid question sir, but is it false to state that the value of voltage is what allows the current to flow through human body, according to Ohm's law V=RxI? in this case, the higher value of current that can go across the body is determined by human body resistance, isn't it? therefore, lower is the voltage, lower is the current that can flow if resistance is constant. so if voltage is low, severe damages should not occur . where am I wrong?
High Voltage, low current will not kill you. I touched the vdGraaff which was at 300,000 Volt. The curgent through me was very low. I am still alive.
+Lectures by Walter Lewin. They will make you ♥ Physics. this is clear to me but I believe that voltage like 12V (as it is in car batteries) even if current may be quite high, the current that flows in the body is usually low due to resistance, which may vary from point to point and which is influenced by other different elements, right?
The audience were so dumb... Just responding in laughs... No answers to the question such a great professor... When he wanted a volunteer, after 5 mins a girl came..
Sir I need your mail plz
it's no available
Anybody else watching this during the super blood moon and getting how it works right now?
Good indoctrination here.
:)