The Science of Light and Lasers | Szydlo's At Home Science

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Күн бұрын

The laser is a key part of so much of our modern world, from fibre-optic cabling to eye surgery.
The origin story of lasers goes all the way back to the pioneering work of Isaac Newton. Join Andrew as he spins a tale of the the study of light and lasers, from Newton's prisms to the Nobel prize winning laser photochemistry of George Porter.
Andrew would like to thank Steve Conduit, physics technician at Highgate School, and Jonathan Ryder, precision engineer, for their considerable help in the preparation and explanation of the demonstrations on this talk.
Chapters:
00:00 - Introduction
03:50 - What is a laser?
06:28 - Newton and the prism
09:42 - The wave theory of light
10:50 - Everyday types of light
14:41 - Young and diffraction
16:24 - Dalton's atomic theory
17:50 - Lines in the solar spectrum
20:00 - Faraday and electromagnetism
22:45 - The spectroscope and spectral analysis
29:14 - Matter and light
35:20 - Crookes' radiometer
39:12 - JJ Thompson and the electron
41:29 - Planck's constant
45:08 - Albert Einstein and the photoelectric effect
47:25 - Looking inside the atom
50:54 - Exciting electrons and the laser
53:00 - Metastability
54:45 - The first lasers
56:20 - A modern gas laser
Andrew Szydlo is a chemist and secondary school teacher at Highgate School, well-loved by pupils and Ri attendees alike. He has given public lectures around the country, been featured on TV shows and has become a popular regular face on our channel.
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Пікірлер: 227

@joeelder8526 3 жыл бұрын

These series of videos from Andrew have been absolutely brilliant. You don’t need massive budgets for animations and CGI the simplicity of someone’s passion and an ability to communicate is priceless. I wish I had a teacher like Andrew when I was learning sciences.

@esecallum 3 жыл бұрын

HE NEEDS TO CUT DOWN IT DOWN 2 OR 3 MINUTES. NO ONE IS WATCH A HOUR LONG BOREFEST.

@milesy35 3 жыл бұрын

Ohh there's a series, first one I watched so better find another, BBC4 is now officialy sacked

@inziify 3 жыл бұрын

@@esecallum i am watching it... If u want short vidoes go to tiktok

@esecallum 3 жыл бұрын

@@inziify yes he should be doing tiktok videos this will stop his boring waffling and more people will watch him. You could the video down to a few seconds

@frannelwokatega4057 2 ай бұрын

@@esecallum you are not looking to learn anything if you want short videos

@beamer.electronics 3 жыл бұрын

I'm nearly 70 years old and still with a headful of unanswered questions. Thank you, Andrew, for successfully answering many of them over the years - one by one. You are a master communicator of science, and one is never too old to learn :)

@cosmics999 3 жыл бұрын

Dr.Szydlo is an inspiration to all those who want to study or learn anything. God bless him!

@marilyntanis6097 3 жыл бұрын

Laser

@jkobain 3 жыл бұрын

I think that the only man on this entire planet whom I could listen to forever and never ever get bored with is certainly Andrew Zbigniew Szydło. Stay safe, folks; and thank you for another episode!

@cjslasinski9841 3 жыл бұрын

I must admit, Irving Finkel, curator of the British Museum may have had him beat, however on a scale of 1-10, Finkel is a ten, but being of Polish extraction, Andrew Zbigniew Szydlo is an 11! I love to listen to both!!

@Brusselpicker 3 жыл бұрын

Andrew could lecture on paint drying and make the process of evaporation fascinating. I love his enthusiasm for his subject and his obvious love of sharing that with the audience, a wonderful communicator.

@rarrawer 3 жыл бұрын

That does sound like a good challenge.

@MadScientist267 2 жыл бұрын

Also sounds like the same comment copied and pasted over and over again

@TheRoyalInstitution 3 жыл бұрын

Guess who's back? As school is starting up, Andrew still found time to make a few more videos that he kindly allowed us to share with all of you. And for this very special video, Andrew would like to thank Steve Conduit, physics technician at Highgate School, and Jonathan Ryder, precision engineer, for their considerable help in the preparation and explanation of the demonstrations on this talk.

@guitar8173 3 жыл бұрын

The royal institute one of the best

@nahulseyon54 3 жыл бұрын

Could u plz make a plasma blaster as shown in Iron man? (Only if u can do) This is just a request of your TOP FAN. Will u please accept my request? If u can plz also make jet propulsor.

@BariumCobaltNitrog3n 3 жыл бұрын

Precision Engineer, well of course you need one for lasers. Andrew is so thorough.

@ahmdabdallah5811 3 жыл бұрын

God has said in the Quran: { O mankind, worship your Lord, who created you and those before you, that you may become righteous - ( 2:21 ) [He] who made for you the earth a bed [spread out] and the sky a ceiling and sent down from the sky, rain and brought forth thereby fruits as provision for you. So do not attribute to Allah equals while you know [that there is nothing similar to Him]. ( 2:22 ) And if you are in doubt about what We have sent down upon Our Servant [Muhammad], then produce a surah the like thereof and call upon your witnesses other than Allah, if you should be truthful. ( 2:23 ) But if you do not - and you will never be able to - then fear the Fire, whose fuel is men and stones, prepared for the disbelievers.( 2:24 ) And give good tidings to those who believe and do righteous deeds that they will have gardens [in Paradise] beneath which rivers flow. Whenever they are provided with a provision of fruit therefrom, they will say, "This is what we were provided with before." And it is given to them in likeness. And they will have therein purified spouses, and they will abide therein eternally. ( 2:25 ) Quran

@nahulseyon54 3 жыл бұрын

@@ahmdabdallah5811 why did u say that?

@puffinjuice 3 жыл бұрын

Love the lack of powerpoint. This type of teaching feels very personal. Love it!

@demoncloud6147 3 жыл бұрын

I didn't even notice that there was no powerpoint

@evolvedcopper2205 3 жыл бұрын

Gotta say I agree. Teaching even though it warrants a lot of repetition, it has lots of free flowing passing down of knowledge. With Andrew I see a person who loves what he knows, and also enjoys sharing his knowledge

@ahmdabdallah5811 3 жыл бұрын

What Is Islam? Islam is not just another religion. It is the same message preached by Moses, Jesus and Abraham. Islam literally means ‘submission to God’ and it teaches us to have a direct relationship with God. It reminds us that since God created us, no one should be worshipped except God alone. It also teaches that God is nothing like a human being or like anything that we can imagine. The concept of God is summarized in the Quran as: { “Say, He is God, the One. God, the Absolute. He does not give birth, nor was He born, and there is nothing like Him.”} (Quran 112:1-4) Becoming a Muslim is not turning your back to Jesus. Rather it’s going back to the original teachings of Jesus and obeying him

@Laerthor 3 жыл бұрын

puffin juice and the pocket watch in his pocket

@stylis666 3 жыл бұрын

I get slightly aroused every time he says "experiment", because he actually does them to show it

@77dreimaldie0 3 жыл бұрын

His (successful!) attempt to pronounce scientists’ names correctly regardless of their language of origin is admirable!

@hoyporhoy3657 3 жыл бұрын

He pronounced the names correctly but I couldn't help but notice he wrote "Kirchhoff" incorrectly. Anyway, I completely agree with you that it's admirable!

@pev_ 3 жыл бұрын

That is because he is not American :)

@moiquiregardevideo 3 жыл бұрын

@@pev_ it is true that somebody living in Europe and who wants to learn the correct pronounciation of different names has the task easy. Here, in United States, there is no such linguistic diversity. I would argue however that French people insist to pronounce names in a very distinct way and would be shamed for trying to diverge from the "correct" way shared by all French.

@travislee9396 3 жыл бұрын

With men like him it’s a matter of respect. How does one pronounce his last name?

@sujatapawar6351 3 жыл бұрын

I love the way of teaching. He is just a fabulous teacher. no powerpoint presentation,only a real teaching.

@vidyalankargharpure 3 жыл бұрын

Mr. Szydlo is a wonderful teacher. I deeply appreciate his tireless efforts. Mr. Szydlo explains the subject in an attractive manner. His lectures are carefully designed with subject matter and demonstrations. I watch his videos from India and I wish there should be atleast one Szydlo in India. Sir, I am very much thankful to you and expect more and more videos on various science topics.

@Armistice0 3 жыл бұрын

Andrew Szydlos demonstrations are always so succinct.

@evbobdemon6994 3 жыл бұрын

Thank you. I'm nearly 50 and I love this man's knowledge and the way he conduct's his lessons.

@chocolatejellybean2820 3 жыл бұрын

I'm 50 plus and finding so many learning opportunities these days.. never understood this at school

@evbobdemon6994 3 жыл бұрын

@@chocolatejellybean2820 I did not learn at school as I'm nearly a spag, but I have learnt lots through video's like these.

@johsenior1535 3 жыл бұрын

Wonderful demonstration! I love how he explains every intermediary step scientists went through throughout history to finally understand all these properties and use it to construct the laser

@PhysicsMathMan 3 жыл бұрын

By far my most favorite teacher on RI

@robertwilliams204 3 жыл бұрын

Brilliant introduction with the fire. It wouldn't be a talk with Andrew without something being on fire.

@alancurtis9155 3 жыл бұрын

Thank you Andrew, another great talk. It is a good job we have people like Andrew able to impart so much history of science. His science book library must be amazing.

@subliminalvibes 3 жыл бұрын

Laser light is incredible. So versatile! I use lasers to make holograms at home. Manipulating single wavelength light to create holographic diffraction patterns is the closest I can get to toying with quantum physics, and I love it. Also; thank you to The Royal Institution for allowing the Professor to produce this video since the wonderful Christmas Lecture on the subject from the '80s is yet to be recovered.

@TheRoyalInstitution 3 жыл бұрын

Oh it's less about us allowing him, and more about Andrew being one of the most wonderful human beings and allowing us to share his incredible videos with all of you.

@subliminalvibes 3 жыл бұрын

@@TheRoyalInstitution Good morning. How wonderful! His enthusiasm certainly is infectious. Please thank Professor Szydlo for ALL his videos (especially the really long ones), with admiration from Australia.

@duynk 3 жыл бұрын

Fascinating lecture. I am up at 2AM watching this. Thank you professor.

@alancurtis9155 4 ай бұрын

Dear Doctor Szydlo, I keep coming back to watch this most brilliantly fascinating lecture, one of many in your "at home science" series which kept us sane during the difficult times of covid. Thank you so much for this.

@laurahaaima1436 4 ай бұрын

I wish I had acces to this mans enthusiasm in my younger days.. I would have learned a lot more..

@2flight 3 жыл бұрын

this lecture is a quantum enthusiasm packet!!! an explosion of enthusiasm that is contagious!

@mereblue 3 жыл бұрын

I’m teaching waves and light currently so this is perfect timing. Can’t wait to spend an hour with Andrew!

@solomonlalani 3 жыл бұрын

Absolutely admiring to see how he got excited on Planck and Einstein!

@cndbrn7975 Жыл бұрын

That lecture was awesome. Should have been on the Royal Institute or a Ted talk. Definitely glad I stumbled upon this Professor. Sub

@magickpalms4025 3 жыл бұрын

amazing lecture, thank you so much. love the story about Planck switching from music to physics.

@sharadkumarsingh8972 3 жыл бұрын

I love videos done by Andrew, no matter topic. Keep it up!

@Zenodilodon 3 жыл бұрын

One of my favorite lecturers speaking on my favorite topic. I have my lasers ready so I can follow along :P

@phonotical Жыл бұрын

I knew if I checked the comments I'd find you here! 😅

@myriaddsystems 3 жыл бұрын

For first time in 55 years I actually understand how a laser works, due to this fine gentleman's humility, charm and sheer talent for imparting good learning.

@k29king1 3 жыл бұрын

This guy makes learning enjoyable

@KaleOrton Жыл бұрын

The common white led is a uv emitting diode with phosphor coating creating white. There are RGB leds that also approximate white, but they are also used as 'colour changing' light sources. Dziekuje bardzo Mr Szydlo - I love your style! 🙏👍

@tobybowden4009 3 жыл бұрын

superb i love the Ri, take my son there whenever i can, its a superb place

@brunomarcato4591 3 жыл бұрын

Very cool, glad for your opportunity! I will go there when visiting the U.K. :)

@Peter_S_ 3 жыл бұрын

Your son is a lucky lad.

@brunomarcato4591 3 жыл бұрын

@@Peter_S_ Yeah, going to the Ri with your parents is a dream come true!

@ez5201 3 жыл бұрын

Absolute masterpiece of explanation on scientific issues! What a great legacy!

@prachethire812 3 жыл бұрын

What facinated me was the fact that Faraday actually made a practical setup to bent light by using huge magnets to prove that light is a electromagnetic wave.

@PlanckRelic 3 жыл бұрын

That statement was actually a tad confusing to me, because the path which light takes isn't bent by magnetic fields. What is 'bent' is the orientation of the polarization of that light, the eponymous 'Faraday Rotation' used by astronomers to map things like the magnetic fields in our own galaxy. Nonetheless a monumental observation in its era.

@bernardmiller5347 3 жыл бұрын

He’s is talented and a teacher by profession and I’m glad he’s making smarter people.

@evolvedcopper2205 3 жыл бұрын

This man is one of a kind. I'm watching a stack of Andrew's stuff in recent days when I'm free. Lots of things in my school education looks like a skeleton when i hear him, he has truly brought new dimensions to my understanding of many things

@pheargoth 3 жыл бұрын

I absolutely LOVE all of Andrew's videos! I love watching someone talk about a subject that they're truly super knowledgeable and passionate about.

@TheGradeFootballer 2 жыл бұрын

I am a simple man. I see Andrew Szydlo's RI lecture, I click.

@JoshuaKane. 3 жыл бұрын

I've been hangin' for a new episode with Mr Szydlo!! woohoo! fantastic!

@72polara 3 жыл бұрын

Thank you Dr. Szydlo. The memories of playing around with a HeNe laser from the local electronics surplus store....

@vmb326 7 ай бұрын

Referring to Max Planck as "Maxy boy"..... love it ❤

@HawthorneHillNaturePreserve 3 жыл бұрын

Some people are just gifted with intelligence and passion to be able to communicate and share their knowledge!

@Gribbo9999 3 жыл бұрын

I am old enough to remember the invention of the laser. At the time it was seen to be "an interesting invention looking for a use". I think we found a few since!

@joltsofdeath 3 жыл бұрын

LONG LIVE Szydlo

@TheSpoonyFox 3 жыл бұрын

I tuned in to hope to get some rest because a lot of the RI videos are relaxing... But I couldn't take my eyes off this lecture. Well done, Dr. Szydlo! Thank you for the informative lecture. :D

@DiCasaFilm 10 ай бұрын

"Szydlo is just Szydlo." Love it.

@beachboardfan9544 3 жыл бұрын

Loving the Szydlo series!!!

@mynickwaspirated 3 жыл бұрын

Great video, thanks a lot, Dr. Szydlo.

@raulcheva 3 жыл бұрын

Amazing lecture. I love his "no nonsense" style of communicating knowledge.

@janice2911 3 жыл бұрын

What a passionate man! Just finished watching Feynman’s Auckland lectures and this one made everything so complete, Reflecting on it made me realize what probabilistic wave means for a particle! Thank you so much!

@hypnotourist 3 жыл бұрын

What a great trip through time and ideas !

@Ma_X64 3 жыл бұрын

I like this remote lecture more than that was filmed in institution.

@extrastuff9463 3 жыл бұрын

Another excellent video presentation as always, I was quite familiar with most of the individual aspects discussed here. But the chronological presentation with a brief overview of a few essential principles has a nice touch to it. Just one tiny technical little nitpicking issue, when the white LED torch is brought up it is mentioned that there are 3 different colour LEDs inside. While those exist it's usually only when you can deliberately control the individual components to produce what appears to us as some kind of light colour. Practical white LEDs typically work based on a blue LED (most efficient type currently) which is then absorbed by a mixture of phosphors which then emit it at a different wavelength. A similar thing happens in both compact fluorescent lamps and the tubes, in there the primary light source is typically ultraviolet light from a gas discharge though that gets converted into visible light. While it could've been interesting (and somewhat appropriate as well given the subject) to go over these things, I don't think going in depth into more tangents with an even longer video as the result would be desirable for some people. That said I do remember dichromatic, trichromatic and even tetrachromatic white LEDs being around, where 2, 3 or 4 different monochrome LEDs get mixed to appear to us as one colour. I don't think I want to know about the colour rendering of the first to, maybe a tetrachromatic one could be acceptable but I'd rather go with less efficient but more spread out phosphor converted spectrum.

@stevetproject 3 жыл бұрын

Great to have people in the world who care....

@GeoffBernard 3 жыл бұрын

As i read through the comments, I want to thumbs up all of them! RI viewers are amazing people! Thanks to everyone that posted a comment - you are restoring my faith in humanity!

@Busshanta 3 жыл бұрын

Knowledge in times of isolation, thank you

@swadeshtaneja3512 3 жыл бұрын

Wow enjoyed thoroughly. What a great teacher. 🙏🙏🙏🙏🙏🙏🌹🌹🌹🌹🌹🌹Feel lucky

@Garmashua 3 жыл бұрын

Many thanks for sharing your point of understanding!!!

@thenobleone-3384 3 жыл бұрын

Bill Nye the Science Guy is what got me obsessed with Science. So if it wasn't for him I probably wouldn't have had such of an obsession for this field

@appleking9836 11 сағат бұрын

Great man, great video!

@jbrethous 3 жыл бұрын

Great teaching, amazing work. Thank you, you rock.

@namelessrationalist636 3 жыл бұрын

Thanks for the Enlightening Lecture!

@Kiuman 3 жыл бұрын

One corner to rule them all! Love it!

@zakirzak1494 3 жыл бұрын

Felt so nice listening to him. Learned a lot ...thank you.

@assassinzeusplays 3 жыл бұрын

I never get tired of watching his experiments❤

@lampanish 3 жыл бұрын

An enlightening lecture.

@satyamshukla381 3 жыл бұрын

WONDERFUL INVENTIONS BY WONDERFUL SIR EXPLAINED IN A WONDERFUL WAY,THANKU.

@ricardoderas5638 3 жыл бұрын

@43:55--"It was at this stage that the digital world was born....At the subatomic level, dear friends, the world is actually different. It's quantized. You can have yes or no, zero or one...."

@mandibourget3434 3 жыл бұрын

I love these videos!

@maryhyphenkay 3 жыл бұрын

Does Szydlo have his own channel because I could watch and listen to his lectures for hours.

@TheRoyalInstitution 3 жыл бұрын

We don't think so, but you can check this playlist to see if you've missed any - kzfaq.info/sun/PLbnrZHfNEDZxPZ369tAF0wjnNo-A3EcDi

$@fractalnomics$

@fractalnomics 3 жыл бұрын

Fantastic lecture.

@davidrobinson7112 3 жыл бұрын

It might be very educational to have this gentleman lecture on the science of paint changing state from liquid to dry solid. I am not being silly or insulting.

@tarunsharma8651 3 жыл бұрын

1:00 that was certainly the goblet of fire. I really hoped for a champion's name to come out.

@-metaldetectorist-3713 3 жыл бұрын

Brilliant love watching these very educational. I like the one on iron. Reminds me of my science teacher. But unfortunately I appreciate it more these days than my youth 🌾💐👍

@STali37 Жыл бұрын

Brilliant lecture sir🙏🙏

@SimonSozzi7258 3 жыл бұрын

So beautiful! 🙏

@kenishabasnet8764 3 жыл бұрын

When I listen sir your videos my mind automatically concentrates .

@BariumCobaltNitrog3n 3 жыл бұрын

I wonder, I don't know, but I ponder why public speakers take on a certain style, most likely regional, that for example, seems to indicate the speaker's overwhelming desire, no...obligation to make the listener feel that this experience was worth the price of admission, worth his while to take the time and energy to attend (attending at home is certainly as much a commitment) to what is billed as an educational and enlightening and (one hopes) entertaining experience. The level of excitement about the subject matter never drops, and every detail is deemed worthy of inclusion, such as the retiring of the colored fires, being put out now, with water, soon to be extinguished, not to worry and there. Now Lasers. Aren't they amazing? Yet ubiquitous to everyday life... I think we here people will always feel a bit late to the party knowing that some of your houses are older than our country. I do like this speaker though, a lot. Never boring haha, most understated comment Janus.

@georgeprout42 3 жыл бұрын

That torch, wow flashback time, had a few of those back in the 70s. Immediately thought of the ever ready number 8 battery that they took.

@byronwatkins2565 3 жыл бұрын

The probability of an energetic thermal fluctuation is proportional to exp(-E/kT). Assuming energy can have continuous values and finding the expected average for different temperatures =integral(E * exp(-E/kT)) leads to unbounded energy as E-->0. Planck tried E=nhf using summation =sum(E * exp(-E/kT)) with the idea of allowing h-->0 afterward and this led to the geometric series with r^n = (exp(-hf/kT))^n whose sum is 1/(1-r)=1/(1 - exp(-hf/kT)). Unfortunately, letting h-->0 still yields unbounded energy in the low energy frequencies; but the model fits the black body spectrum exquisitely.

@srboromir452 3 жыл бұрын

Aren't some LED's a phosphor layer that's excited by UV light or the like?

@cambridgemart2075 3 жыл бұрын

Yes, most modern high efficiency LEDs are short wavelength blue-violet diodes with a phosphor layer to produce one or more longer wavelengths.

@jdrissel 3 жыл бұрын

Yes, microspheres act as a very tuneable wavelength converter. With phosphors the chemistry determines the emitted colors, with microspheres the size determines the wavelength of output. For use in LEDs, a range of sizes is used, many thousands per led at the minimum.

@teresashinkansen9402 3 жыл бұрын

@@jdrissel Microspheres? you mean quantum dots? (3 orders of magnitude smaller)

@jdrissel 3 жыл бұрын

@@teresashinkansen9402 maybe so, I did mean something small enough that it took an electron microscope to see it.

@fburton8 3 жыл бұрын

Nuffield A-level chemistry textbook - recognized the cover and colour plate of spectra straight away. Ah, nostalgia.

@hutlazzz 3 жыл бұрын

thanks to share this knowledge sir

@RohdeFischer 3 жыл бұрын

Fantastic, two things though. I get the feel that he has loads of more interesting things he could tell, and it feels a bit like he's trying to rush through. Making it into two long videos would be amazing. Take your time, it's an amazing topic and he's amazing at explaining, we would love to spend the time on multiple videos too :) A technical detail, it seems that the audio is recorded by the camera, but it seems Andrew actually have a clip on mic. Would it be possible to update the audio with the recording from that mic?

@joeflosion 3 жыл бұрын

"Szydlo is only Szydlo" but we love Doc Szydlo

@FredStam 3 жыл бұрын

This is quite good

@sebastianelytron8450 3 жыл бұрын

More than two seconds of silence: * exists * Professor Szydlo: Allow me to introduce myself

@aa55claa55cl 3 жыл бұрын

omg. I think this should be the standard in UK and US education style. KZfaq based education, school only as accessory in experimental learning ( simulate work place condition )

@numanh8391 3 жыл бұрын

Using laser to cool objects is 😎

@byronwatkins2565 3 жыл бұрын

Stimulation emission came from Planck's law also. Einstein realized that the probability that an atom would absorb a photon necessarily was proportional to the number of photons present. Similarly, the probability that an atom would emit a photon was proportional to the number of excited atoms. However, when he tried to establish a thermal equilibrium between these two, he found it necessary to add an emission term proportional to the number of photons present before the resulting temperature dependence agreed with Planck.

@Peter_S_ 3 жыл бұрын

I'm quite surprised at the degree of error in describing the LED torch. It is not made from red, green, and blue LEDs. Poppycock. White LEDs are made from either a blue or purple LED and phosphors to produce the wavelengths longer than the blue or purple LED. Most white LEDs use a blue gallium nitride LED with emissions centered on roughly 470nm (Nichia) or 440-460nm (Lumileds) while the devices with a higher color rendering index use 405mn purple LEDs. All the rest of the color is the result of phosphors.

@vripscript 3 жыл бұрын

your incorrect on a few points, I wont bother explaining

@ashcroftg1 3 жыл бұрын

Peter S There are "2 ways" of producing LED white light.....1. Red, Green & Blue 2. Similar to florescent light..........source Wikipedia but is widely known in science. Goodluck.

@cambridgemart2075 3 жыл бұрын

@Peter S Indeed, that's the way white (and also most single colour LEDs) have worked for a decade or so.

@1boobtube 3 жыл бұрын

@@cambridgemart2075 nope. remove everything in parentheses.

@cambridgemart2075 3 жыл бұрын

@@1boobtube Nope, read who I was replying to!

@andymouse 3 жыл бұрын

Wonderful lecture! I wonder if the LED ( Light Emitting Diode ) in the bottom torch was a blue LED behind a White Phosphor, as opposed to an RGB ( Red, Green, Blue ) LED ? the former is far cheaper and more readily available in handheld torches.

@RonLaws 3 жыл бұрын

I have a correction at around 13:20 - White LED's are not a combination of red/green/blue LEDs but are actually near ultra violet/blue LEDs (~465nm) with a phosphor coating over the top of the silicon chip that lengthens some of the blue light towards yellow

@SCREENDOORONSUBMARIN 3 жыл бұрын

WALLET CHAIN! It's like I'm in high school again.

@heyrim72 3 жыл бұрын

Most of the white LEDs are actually similar to a fluorescent tube. They use blue LEDs and a layer of phosorous which converts the blue light to mostly white light. Never the less, some of them use actually use a mixture of single color LEDs to create the impression of white light.

@Gribbo9999 3 жыл бұрын

I have to say these lovely colour pencil and paper presentations are so attractive after sterile PowerPoint slides. But I have to say Andrew's presentation is much better than seeing Roger Penrose fumble his way through overhead projector sheets which is just distracting and cries out for PowerPoint!

@gepeto032 3 жыл бұрын

Charity is often respectable. Respect should never be charitable.

@Sammasambuddha 6 ай бұрын

The David Attenborough of science.

@xBoLtiCuS Жыл бұрын

First of all, thank you for this video! I am not convinced that light has a speed though and here is why... Is it possible to trap a beam of a laser between mirrors and then turn the laser off to demonstrate lights ability to travel without the source being active? I don't think that an argument of light losing energy to the mirrors would suffice as to why it could not because light is said to be a self propagating wave. Further more these waves are probably spirals but appear as though they are waves on a graph depiction which is limited to a 2d frame of reference.