How a Laser Works

Bill shows how the three key characteristics of laser light - single wavelength, narrow beam, and high intensity - are made. He explains the operation of a ruby laser - the first laser ever made - showing how electronic transitions create stimulated emission to give coherent light, and then how the ends of the ruby cavity create a narrow wavelength highly collimated beam. You can learn more about laser in the EngineerGuy team's new book Eight Amazing Engineering Stories www.engineerguy.com/elements

[@zurkel1098]

And now we use them to fuck with cats.

[@cortster12]

We use them for almost everything.

[@hoopsmontrer9887]

+Cortster I use mine to point out stars

[@holycrusader8372]

i use them for blinding cats

[@inactive9384]

Holy Crusader your cruel

[@shakenbacon993]

*you're

[@thefakedeal]

I love how mark hamil explains lasers

[@nickhighland799]

he should have shown us his lightsaber, I'd like to know how that works.

[@Nothing_serious]

Samir Shrestha He's tired of Batman

[@Tio-Nino]

Beam me up! Scotty!!!

[@ingrid2033]

Can mark hamil explain how does mark hamil explains light ?

[@MsAhutch]

This is Clark Hamil, his lesser known but much smarter older brother

[@jaykay4137]

I know the words, but I don't understand them in that combination.

[@Supermario0727]

I understand some of this. Hugh school chemistry will teach you some of this stuff.

[@ryangis431]

John Stuart Hugh School? Hugh Mungus has a school?

[@louf7178]

Jay Kay lol. Yes, I have the winning lottery numbers. Just have to get the right order.

[@KM-fckutube]

Jay Kay, those were my thoughts exactly.

[@arkhe1n107]

Thankfully you're not alone.

[@justinsander7654]

I have always taken time to explain how things actually work to my kids when they ask and having discovered your video's I am proud to say they were absolutely glued to the screen. KZbin should have more educational material like this. To bill directly you sir make the learning fun your selection of props examples and references are excellent. You have taken some very complex subjects and made them interesting and fairly easy to follow Thank you.

[@musictechnique]

I'm not familiar with your career Sir, but if you don't do voice over and narration work then the world is missing out.

[@ieuanhunt552]

DPS he should definitely do a narration of that book he promotes at the end of every video. I would buy it

[@munjee2]

DPS check out his audio books

[@computername]

Not sure what it is, but something tells me he must be doing some tech stuff. Maybe even engineering..

[@chillpillology]

Reminds me of bill curtis a little bit

[@Plexiate]

This guy looks 16 and 61 at the same time. (Loved the video.)

[@Bigmilklord]

Wow hello there

[@silkwurms]

Last place Id expect to see him

[@Bigmilklord]

@@silkwurms same

[@shaneh1003]

It's the haircut.

[@joshuacabezas8061]

why is this true

[@gregsalcedo4857]

In the early 60s, somebody wrote 'The laser is a solution looking for a problem'.

[@myearshurtnoone1367]

sounds like hysteria to me

[@spoonikle]

+myearshurt Noone it's based on an old saying "hammer looking for a nail". imagine your local overzealous neighborhood watch desperate to feel useful and trying to solve problems that are not actually problems. basically back in the day nobody thought there was a use for lasers and laser advocates where just running around with hammers smacking at everyone's inventions.

[@kriswilson5305]

spoonikle You clarified that wonderfully. Thank you.

[@sciencecompliance235]

"Laser inventor DESTROYS critics in this EPIC video"

[@ThZuao]

Hapens quite often in the engineering world. I bet the people behind the creation of the LASER itself didn't expect much off it. Maybe just the Rangefinding aplication. Hero of Alexandria didn't expect the Aeolipile to be more than a mere curiosity. It took 1700 years for someone to figure out the principles behind the device's inner workings and do something with it, and when it happened, it changed the world forever.

[@WarriorAjk]

This video is professional as fuck!

[@LazyScoutJace]

Totally reminds me of FilmmakerIQ

[@S....]

Could you please give me a definition of a professional fuck?

[@sebastiang8634]

Prostitution?

[@aholicrealm2850]

A. Goraya lol

[@robertthomas4329]

Unlike you

[@fredrickfowler594]

Dear Bill, thank you so much for so succinctly explaining how a laser works. I sort of had a general idea, but your video is so comprehensive and easy to understand. Science has always been my favorite subject, and being that I am writing one of my books on focusing, I decided to use the laser as an example of how light is focused, and your video was a God send in my understanding it. It gave me the tools that my tired mind from writing for the last fourteen hours needed to complete the chapter that my deadline requires. Bless your heart, and thank you very much once again, Fredrick Fowler

[@DeadBread.]

Its been Seven years, How's Your book coming?

[@engineerguyvideo]

At the publisher now!

[@angelostodomingo5570]

@@engineerguyvideo bill please make more videos

[@bonnome2]

You should get paid by governments for making these high quality and very clear videos.

[@beybladeguru101]

Anything the government does, it fucks up, or is vastly inferior to the private sector.

[@Lorpark]

ZootMiBalot why not?

[@Lorpark]

ZootMiBalot why?

[@jesusec100]

Why not?

[@dannywilliamo]

Lol everyone roasted you, but he is a University of Illinois professor, and is therefore paid by the State of Illinois in part to make these videos, as well as teach a class at the school introducing engineering to freshman and sophomores.

[@skidooshlayman12]

And this is why Cyclops's visor is made of ruby.

[@jonathanw1019]

Ruby quartz. They're not the same.

[@josefish5193]

@@jonathanw1019 three year old comment....

[@jonathanw1019]

Josefish that’s fine. 3 years, 90 likes and not a single person corrected them. Somebody had to do it eventually.

[@wsketchy]

@@josefish5193 The wonder of the internet is that it's not like you're speaking to an empty house, the message will still be there when the occupant returns. You can say something at any time and eventually someone will see it.

[@DarkAngelEU]

@@wsketchy Kinda creepy though, isn't it? We're constantly looking at the past as if it were present. Our future is becoming history within this space outside of time.

[@Naton]

Nice voice....good presentations... but still didnt understand.

[@ChesterChi3]

To understand how lasers work, first you have to already know how lasers work...

[@strong8705]

Maybe it's a teaser for a book.

[@5udimax]

@@ChesterChi3 what is this, recursion?

[@dougschmierer7750]

He uses too much jargon while making few attempts to define anything. His visuals are simple, which is good, but they attempt to cover too many concepts, which is bad. His sequencing is too rushed and lacking in transitional cues; he jumps from one feature to another without clearly concluding the previous feature or introducing the new feature, so part of your confusion is that you're trying to figure out how new information relates to the last when it likely doesn't; they simply share a theme of "lasers". Basically, this guy is a prime example of why companies pay technical writers to explain engineers' products for them.

[@johnjordan3552]

You need to know some at least beginner atom physics

[@DonlineUK]

Excellent description of how a ruby rod laser works. Seen it in many diagrams over the years - but this explanation brought it all home for me. Well done!

[@drakepomeroy2861]

I just realized he teaches at the college in my town. So cool!

[@worshipwithjonathan]

what place, which college?

[@tribot_leader]

What does he teach?

[@luise213]

@@worshipwithjonathan UIUC I assume, given what the caption shows at the beginning of the video when introducing him

[@rabiaaslam3186]

You must visit

[@worshipwithjonathan]

Im in germany, half way around the world haha

[@khalidikan3801]

this is the first time I saw an Arabic translation on youtube made by a non Arab great work thank you for your effort and to make your knowledge accessible almost to all human kind

[@Mukeshmiktecrep]

I watched so many videos but that is the video which deeply clarified the working and the cause of Laser beam.

[@ethnicdancer]

Thanks Engineer Guy! My students will love this as much as/more than I did!!! We're studying atomic structure.

[@ft_lesserchungus1192]

engineer gaming

[@w04h]

@@ft_lesserchungus1192 engineer gaming

[@noggan]

I love these videos because learning is fun, thanks for making some of the best videos on KZbin.

[@JaseewaJasee]

your ability to keep things interesting never ceases to amaze me!

[@PacoOtis]

Bill, we are very big fans of yours and must tell you that you present this video as if you are running late and have to catch a bus! This one appears rather below the "bar" you typically have for yourself. Thanks for the effort but you just might ponder this format! Best of luck!

[@mydogwasbrian]

2:35 - 3:34 so, basically magic.

[@frankytoad12]

Jesus did it.

[@pumpjackmcgee4267]

Lasers of Jesus would be an awesome band name.

[@frankytoad12]

I believe you're onto something my friend.

[@pokemonplanet4153]

Alex Myers damkig

[@MrMalibujunkies]

fotoelectric effect :)

[@samuelchristmas]

Love these videos! Your channel is often the first place I hear in depth about these remarkable feats of engineering. You're doing great work for laymen such as myself :D!

[@DjRishi18]

Why am I getting this video recommendation in 2021 and not in 2012. Sir, you were ahead of your time. You need to come back!

[@jeylful]

Very well explained. I knew about the ruby laser but I didn't know its operation. Great to have shown the ruby ball glowing when illuminated with blue light. Thank you!

[@rocklobster1976]

I really love this channel . You go precisely into the right depth needed to explain the most important functions. There aren't many groups that will take the time y'all have. I'd compare you to, mr wizard if I could. Maybe even better

[@Observ45er]

+rocklobster1976 In my opinion, Don Herbert is the gold standard... (except for the two things I am aware of that Don (at least his researcher) got wrong). -- Cheers

[@-Maverick.]

yeah

[@riko2965]

i like his voice and what a great clip!

[@akashashen]

Thank you, engineerguyvideo; I love your treatment of the subject matter -- it maintains comfortable rate of change in perspective that ensure the information sustains the interest of the viewer while staying close enough to remain an easy to relate whole. I'm glad I've subscribed.

[@MrJamieBla]

I have to say I read the comments before watching the video and I wasn't expecting to understand it because most of the comments say how complicated it is. Yet to my surprise I understood it and I really enjoyed it, looking forward to more of your videos!!

[@masterchimichanga117]

Made perfect sense thx!! Imma build one now

[@kx65andyx85rider]

Wait what?

[@IliaBaranov]

These videos are fantastic, extremely well explained, and well thought out. Thank you @engineerguy

[@gnsci141185]

When I studied Engineering I just mugged it up without even understanding how it works, but your video is so simple and people can understand it. I have recommended my college and School to share the videos to the students to understand the stuffs. Thanks you so much for these educational videos. I would like to say Thanks in my Mother Tongue "நன்றி"

[@dafnasantillo8422]

I liked it, it was very well explained, although I was hoping to find a little bit more information about the behaviour of the electrons and the different types of emission and absortion of light.

[@kookoon]

I still didn't understood completely. It was interesting anyway.

[@yotams6168]

If you had never learn physics before it maybe will be hard to understand, but if you will be able to understand the basic of it (Bohr Model) I think it will be clear - en.wikipedia.org/wiki/Bohr_model .

[@-Maverick.]

are you alive?

[@engineerguyvideo]

Me or the commenters above?

[@-Maverick.]

@@engineerguyvideo the commenters. Also how did you reply so fast?

[@engineerguyvideo]

I typed

[@OwenKoenig]

I really enjoyed this video, Ill keep an eye for any more you share.

[@orangejjay]

Very well done, my friend. Thank you.

[@ReaLzEdits]

I understood up until 2:19 then I thought.......... ???? So basically I learnt they have rubies in them with some glass beads...... OFF TO THE NEXT SCIENCE VIDEO TO HALF LEARN SOMETHING!

[@oldfrend]

+ReaLzEdits no glass beads. he was just using them as an example of a material that doesn't give off light and comparing them to the ruby that does.

[@ReaLzEdits]

***** See I'm fucked xD

[@oldfrend]

ReaLzEdits ok you want a simpler explanation? see how the ruby shines when he turns the flashlight on it? make the ruby a tube, make the flashlight like a million times stronger, poke a hole in one end of the ruby, BAM, laser.

[@TheFungck]

+ReaLzEdits the video do not explain "stimulated emission". and the picture is not correctly explain the population inversion. in stimulated emission, when light hit the electron to excited state, it will double the income light. Two "mirror" will reflect the light backward and this process repeat many time until "light" are very very strong to exit through the mirror. It is still over simplified but still better then not explain.

[@TheFungck]

+ReaLzEdits "ruby shines in flashlight" is fluorescence not laser....

[@Lodox]

Hey look, it's Mark Hamill!

[@nuclearnyanboi]

sincere thanks for making this video

[@blackbear92201]

Awesome video - thanks for posting!

[@TheShattenjager]

When he said "ruby rod," who else besides me flashed to The Fifth Element?

[@formdusktilldeath]

you beat me to it, by a year no less. UNBELIEVABLE!

[@flappy7373]

i already wrote this exact same thing.. you beat me to it by 3 months and dan beat me to it by a year haha

[@Cammi_Rosalie]

Dan sweetheart, what was that? ...It was BAD! It had no fire, no energy, no nothing! Ya' know I got a show to run here, and it must pop POP POP!!! So tomorrow from 5 to 7 will you please act like you have more than a two word vocabulary. It must be green, okay?

[@Preinstallable]

I have the fifth element on a dvd

[@boomerhgt]

Nobody

[@easterdm]

Was lost by 2:30

[@yotams6168]

If you had never learn physics before it maybe will be hard to understand, but if you will be able to understand the basic of it (Bohr Model) I think it will be clear - en.wikipedia.org/wiki/Bohr_model .

[@Gman333Xferrari]

More videos please Bill! These are amazing.

[@bobbob-gg4eo]

11 years old and still a quality recommendation on my feed

[@newtybot]

If they ever made Jurassic Park real, I’d like you to be the new Mr. DNA

[@R2D6_10]

lmao! dude, you nailed it!

[@keo515]

I learnt about how lasers work last year and he pretty much covered a weeks worth of lectures in this video. Basically, when the ruby is given enough energy an electron will be 'excited' into a higher energy state. when the electron drops energy state, energy is emitted in the form of light, thus laser. Hope that helps a bit.

[@saumitrachakravarty]

The most concise yet coherent explanation of LASER I have ever come across.

[@WeBe3Dprinting]

You explain things so wonderfully and you respond to fan comments promptly. I am so damn subscribed. Keep'em coming!

[@silvermarkjames3181]

Where did you get the ruby from I want some

[@mozkitolife5437]

Great video but the animation regarding the treatment of detached retinas looks like damage control and not welding in back on as described.

[@mozkitolife5437]

@Major Problems Thank you. So I was right? There's different procedures for welding the retina and the animation merely demonstrates how the detachment is prevented from progressing.

[@fensoxx]

Ahhhh! Best channel on any media (for me). Can’t wait until he comes back with more. Thanks!

[@mybluemars]

Amazing presentation!

[@thegardenofeatin5965]

Question: Why specifically Ruby? Do other corundum gems exhibit that same property?

[@Squirrel_314]

I don't think it's the aluminum or oxygen in the corundum that actually gets pumped, but the chromium impurities. Other sapphires might be able to lase, but perhaps not in the visible spectrum, which is rather narrow?

[@jammccockin8304]

Michael yes. my thoughts exactly... but you forgot to carry the 1.

[@casparvoncampenhausen5249]

@@jammccockin8304 😂

[@MrMattsung]

Can you do one on green lasers? Their mechanism is different, and I would love to hear you explain it!

[@fxDELTAx]

The principle is the same which you are still exciting electrons into a higher energy state and allowing the electrons to relax back to its ground state. But the material is different. The wavelength (color) depends on the energy difference of the excited state and the ground state for that is the energy the electron gives off when it relaxes. This would require different materials, many green lasers today are uses semiconductors as the lasing medium.

[@Doom2pro]

Not really, most Green Lasers are using an Infrared laser passed through a small doped crystal that changes the wavelength to green. I believe this is what he is referring to.

[@AeroElectro]

MrMattsung Look up frequency doubling. Or second harmonic generation. Focused light passes through a non linear crystal where SHG effect produces wavelengths of half of the original.

[@ridwanadhipratama7688]

Thank you very much for the video!

[@cassianolara7713]

subscribing to this channel is a treat to oneself

[@monupahal123]

Ok ..i found this channel yesterday and i watched like 20 videos And i know nothing about these engineering

[@ccg4204]

Bill the EngineerGuy vs. Bill Nye the Science Guy. They must fight in a cage!

[@Dargonhuman]

A cage ... made of lasers!

[@rocking195]

Bill nye is also an engineer guy

[@jek__]

Engineer fight! Someone break out the battlebot kits

[@user-cz2cv3dp9h]

This is super amazing and with a nice fundamental explanation. Thanks

[@ThomasGrillo]

I remember reading about this in the book, "Lasers and Masers". Very nicely demonstrated. Thanks for sharing this.

[@magzire]

still no idea lol

[@Tomwesstein]

I kept looking at the four red dots moving to the excited, lower energy and ground state, listening at his explanation and thinken: what on earth is he talking about and why dont these dots decide where they want to be?

[@TSTrueSanctuary]

+Tom Wesstein the dots go into the excited state because they're given energy from the outside light but they always go back to ground state by shooting out the energy as light because theyre lazy dots

[@Jack2Japan]

+Tom Wesstein - Yes, make up your mind(s) already!

[@randominternetprofile8270]

it's really basic quantum mechanics.

[@torugho]

@@randominternetprofile8270 and?

[@carazy123_]

2:14 “lasing”

[@domsusefulstuff]

That was awesome. Now to watch it 20 more times so that I can follow it all.

[@randomvicky939]

Absolutely amazing !

[@norinco8724]

>scans his own book shameless self promotion

[@VamosRapidocom]

Maybe he should scan yours

[@strong8705]

4 minutes ad.

[@gustavoturm]

C'mon, he is doing awesome work, I approve his ads.

[@MilanKarakas]

Wrong about "exact length of the rod". Length does not matter.

[@LAnonHubbard]

That's not what my wife said. Just before filing for divorce.

[@steve24822]

WildMania Correct, it's all about girth!

[@19.sciencetechnology30]

WildMania That's not what she said! lol

[@thatguy431]

Dude this was amazing!

[@GWhizard]

Bill, One of the most enjoyable channels on yt. And a voice of tranquility. 👍

[@daemon9150]

Both mirrors have to be concave for this to work aka for the gaussisn optic to allow a mode

[@psycronizer]

flat out wrong...

[@MultiSciGeek]

Wait... I tought lasers don't need a lamp or a ruby. Was it an older version of a laser he was explaining?

[@MultiSciGeek]

TheArmFlailer Never knew that. How come lasers are so cheap and affordable then? Are the gems impure or very small?

[@MultiSciGeek]

TheArmFlailer Alright I see. Then what is the other laser with gas inside and no lamp? Only switching electron states?

[@MultiSciGeek]

TheArmFlailer Oh ok. Thanks for explaining

[@AlexForencich]

There are many ways to make a laser. All you need is a laser cavity, a gain medium, and a source of energy. In the ruby laser, the flash lamp provides the 'pump' energy and the 'pumped' ruby provides the gain medium. Mirrors create the cavity. However, other things can be used as a gain medium. Helium neon lasers use a combination of helium and neon gas in a tube. Electricity passed through the tube provides the energy, the excited gas provides the gain, and the mirrors at the ends of the tube form the cavity. Diode lasers use specially doped semiconductor to form the gain medium with electric current providing the energy. The laser cavity can be formed a number of ways - cleaved semiconductor faces, distributed gratings, etc. Lasers can be used to pump gain material as well, for example erbium doped fiber amplifiers use lasers to pump energy into a section of glass optical fiber that contains a small amount of erbium to form the gain medium. This can be built into a laser, but more commonly it is used to amplify optical signals in a fiber so that they can be sent hundreds of miles. The gain medium can also be a liquid - lasers called dye lasers circulate liquid dye as a gain medium and can be pumped with flash lamps or other lasers to produce light with specific properties.

[@MultiSciGeek]

Alex Forencich Yeah that's the type I was thinking about, like how do they make all the multi colored lasers. Thank you for explaining :)

[@orgminyak]

Oh I see! Thank you so much for the reply and all your videos!

[@lafo1639]

awesome explanation! thank you for your excellent work on this

[@NVAfilm]

but can you tear apart the Lazer pointer so we can see it.

[@abdulazizalhaidari4574]

engineerguy I recommend you to slow down while speaking to grasp the ideas you want to deliver ! Special thanks

[@thedevo01]

+AbdulAziz AlHaidari - Yeah, the music implies that he's talking to 9-year-olds, but he's pouring information on the listener like they're a fellow engineer.

[@Paradox3121]

These videos are not that difficult to follow... but in any case, you guys know you can watch a video on KZbin more than once, right?

[@ManuAnand97]

+AbdulAziz AlHaidari I don't have any problem. You can turn on the Captions and/or slow down the video at the part what you couldn't understand.

[@thatonedevastatingleek380]

Devo Castler As long as you've taken highschool science you'll get it

[@ix12]

Yeah, he is a bit fast and I have to pause and read, but I prefer it that way rather than if he'd be too slow and make me lose patience, I would never watch his videos then :)

[@panzerdragon1121]

I can't stop watching your videos!

[@Akula114]

I was 5 years old when the first laser was made, and it was a bit of a news item in my small home town because a locally born man, Dr. Charles Townes, had done so much pioneering work on the MASER that led to the LASER . I remember all the Life magazine articles and National Geographics with lot's of great pictures. Despite everything I read, I just couldn't understand how they worked until seeing your video. Now all the pieces and parts just flow together. THANK YOU! PS: Dr. Townes son was famous for another kind of stimulated emission... he was found, well, what was left of him, in a relatively intact car - a victim of spontaneous human combustion. Maybe that was aliens sending Townes a Sicilian message of sorts... "Hey, Pal, you're getting kinda close to our technology... back it off if you know what's good for you!"

[@leejennifercorlewayres9193]

Sad. Probably murdered, God rest his soul. 🙏🌹

[@leejennifercorlewayres9193]

I can't find any information on his son.

[@manualLaborer]

136 people have been shot (and probably horribly disfigured) by lasers.

[@manualLaborer]

hmmm. is she at least 12? >_>

[@seethisth4753]

Where is she?

[@bruhforreal5730]

otacon333x2 I've never seen such an amount of sarcasm radiate through a comment.

[@DallasGreen123]

manualLaborer so funny and original, how do you even come up with something like that

[@19.sciencetechnology30]

This is how the human penis erects! Upon seeing an attractive human, the eyes send a pleasure sensor to the brain, which instantaneously creates a surge of blood through the body's vein channels connected to the males testicles, resulting in an overflow of blood pulsating within a confined area of vessels. As this occurs, a rapid production of energy builds within the testicles producing millions of sperm! When the testicles become full, the sperms are released through the hole in the penis. Once all of the sperm is released, the energy relaxes to ground level, producingin a state of relaxation. The male then becomes very tired and falls asleep for several hours.

[@MacMashPotato]

Ruby rod? like that pop singer in 5th element?

[@carlvincent7756]

Amazing as always. I got the book!

[@MrVenat0r]

Nice simple explanation. Really good.

[@_qaplan_]

مين جى من عند محمود مجدي ☺️🤍🤍

[@abdoskiller1048]

هو انت بتزاكر الدرس قبل ما تاخده ولا ايه

[@tibor29]

Isn't it crazy that the same specie that is able to come up with stuff like this also engages in primitive behaviors such as chopping each other into pieces with machetes or blowing each other up with explosives? Usually for absolutely ridiculous reasons such as ethnicity, race or religion. It's staggering how smart and stupid humans can be at the same time.

[@davidb5205]

That's due to differences between individual and collective behavior.

[@christopherrogers6194]

Well done, articulate accurate and easy to understand, and you have a soothing voice.

[@danielc0307]

Amazing job, Bill. Thank you!

[@LNasterio]

2:30 Good job at confusing the population there, why don't you show an atom instead? why don't you show electrons jumping from different energy levels and release photons?

[@MoeMentos]

This guy is great, but that hair of his could sure use some engineering.

[@hack3line]

+Pharaoh Polystyrene I think in the next video he will show how to do hairstyles like Albert Einstein, Donald Trump, Michael Jackson, Lagertha, Ragnar.. what kind of engineering stuff did the Vikings brought into English world to do a lot of hair styles.. probably will also discuss why Pharaohs hide his hairs under his hat, what kind of engineering did happen during Pharaohs era that the Nefertiti head become soooo biggggggg and hugeeeeeeeeeeee !!!

[@vincenttripi4700]

B. Smith I'm dying laughing.

[@3melendr592]

B. Smith That loss of hair comes from a brain that works so hard there's no nutrients left for hair. Lol

[@Ozlizardking]

B. Smith he must have stockpiled conditioner from the 80s.

[@author4932]

B. Smith engineering xD nice expression :D :D

[@mdouglaswray]

Well done!! Good explanation of the energy states, just enough detail. Thank you!

[@christofergreen214]

For nine years I've been missing out

[@serpentlaw5961]

*This is so well presented and fascinating to watch.*

[@Supersamazing]

I've always wanted to know this. Thank you so much !

[@blink4t2]

You guy are nothing short of awesome. Keep on keepin on. I'll keep hitting that like button

[@fernandorizo9413]

Wow that was really informative! thanks for sharing!

[@christiandaly4281]

I’ve watched like every video, truly the people’s work. Bless you Sir

[@RPG_ash]

Excellent video, love this channel.

[@Gribbo9999]

I think that was the clearest explanation of a laser I have ever seen.

[@CJSwitz]

Had to watch that twice, but I think I understand :D

[@Melkanea]

Found it! MORE PLEASE IT IS AWESOME!

[@guappoo7503]

Awesome! Thank you for the informative video :D

[@BubblewrapMe]

The background music improves this enormously - thank you.

[@LeeXiaoMei]

Ooooo thanks for this video! Really easy to take in and digest. An inspiration for teaching!