A Simple Method For Measuring Plancks Constant

The discovery of Planck's constant in the year 1900 was one of the most important discoveries that catalyzed the quantum revolution. What started as a simple idea to resolve one of the greatest physics mysteries of the time, turned out to be the key to unlocking the quantum realm. While Planck assumed that the constant would be 0 when measured the constant had a definite and real value, meaning that there was a lower limit on the universe. Preforming a basic version of this measurement is actually really easy and we explore the process of that measurement in this video using some LEDs and a diffraction grating.
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[@halbeard2996]

As a little footnote: This method of comparing the minimal voltage for light emission of the LED with the energy of the photons by their frequency/wavelength will only give you a value that has the same magnitude as planck's constant. For deducing a value that approaches the exact value of h you need to know about the specific p-n junction of the diode, because the the applied voltage doesn't excite the electrons to the conduction band but rather displaces the relative energies of the bands before and after the junction. Therefore the LED begins to shine if there is no more potential barrier due to the energetic structure of the junction. In other words, without the knowledge of the properties of the specific LED in use there will always be 'large' systematic error in this measurement.

[@youknow8754]

If you take a Blue LED and carefully apply the voltage do you notice any shift of the spectrum displayed ???

[@LaserJake99]

@@youknow8754 there are spectrum shifts depending on the voltage and temperature of the junction. You can see this dramatically if you overdrive an led.

[@mrigankgupta3490]

Sir, is there any way or any mathematical correction that will let me find accurate value of h? I wish to take this project as my investigatory. Your advice will help.

[@rohansingh1057]

@@mrigankgupta3490 You need to figure out the P-N junction voltage which is usually 0.7 V for silicon but you have to find it for your LED. This can be done by looking up the materials used for making the LED or measuring the voltage across it instantly which most multimeters can't do. The voltage measured from here must be then subtracted from the Measured value(when the LED glows) for more accurate result. Though I must say measuring planck's constant with LED's and diffraction membrane is amazing. This would make a good high school project but for any university student doing B.Sc, BS, B.Tech or Master or Phd, it isn't that amazing there must be better projects than this and 12% error (should be 5% if you use the corrections mentioned above) is like really bad for modern day usage. Recently the value of h has been fixed and we know it with 100% accuracy so.... Pretty cool though using simple instruments to measure a constant significant at subatomic scale.

[@PMoore-ej2ij]

Thank you. That explains why the setup gives 2 eV photons (618 nm) with only, apparently, 1.5 eV electron energy change, which is clearly not possible. If you graph voltage versus frequency, you will see the large systematic error, with a large negative y intercept. The slope does approximate h (in eVs), however.

[@RalphDratman]

This is an excellent video demonstrating a real experiment which yields a real, reasonably accurate result. Thank you so much for making this and posting it for the world to see!

[@wuschelbeutel]

It's difficult to focus on what's being said with the music.

[@JohnVKaravitis]

Wow. You've got ISSUES. #triggered

[@JorgetePanete]

@@JohnVKaravitis stop spamming

[@DarthZackTheFirstI]

not really

[@Ghryst]

you are wrong. you can tell, because i dont agree

[@theultimatereductionist7592]

Agreed, wuschelbeutel!

[@joshwillis1726]

That's actually really neat. I did all of the different components of this experiment separately in university (calculating the wavelength of light based on diffraction, calculating the energy of a photon based on its wavelength, etc) but I never realized that you could use that to measure Planck's constant in such a simple and intuitive way.

[@halbeard2996]

You can't really measure it with this method because you get a systematic error if you don't know about the energetic properties of the p-n junction of the LED. Any university lab course that has this kind of experiment should give this disclaimer (at least to physics students). Otherwise it's a little bit of bullshitting :p

[@courage936]

extremely underrated video, for some reason everything that I could not understand about quantum mechanics now makes sense. subscribed.

[@tony91200211]

This is dope I just learned something new everyday. I thought it was going to be hard to understand, but it was pretty easy to understand.

[@XZenon]

Pro tip: Use a CD with the reflective coating removed if you don't have a diffraction grating. Using the outer grooves works just as well.

[@dozog]

Don't forget that 'd' is between 1.4 and 1.6 um in that case. And that the lines in your grating are curved. So it would be best to use narrow beams.

[@anirudhsathiya3516]

Thanks man

[@jarvenpaajani8105]

Hi, I have been wondering how light polarization affects in double slit experiment. Would love to see a video about that! This channel is just next level awesome, it's quite hard to find all this advanced stuff from youtube!

[@3pacdroru870]

Incredible that these constants can be found experimentally and that their units are rather arbitrary, great video

[@imstevemcqueen]

Very clearly demonstrates considerable knowledge in this subject. Well done.

[@angrybird4636]

Brilliant work, need it for my Physics lab, thank you very much

[@RafaelQuirinoVex]

Freaking awesome !!! Subscribed immediately after the video was over !

[@gilvaniooliveira8850]

I can't hear what you say. The music is too loud :/

[@alexismiller2349]

cool story bro

[@Lyle-xc9pg]

exactly what i was thinking, i didnt want to listen to what he was saying and instead listen to the music

[@paulg444]

just a great, fantastic experiment !!.. Well done!

[@czesaww8232]

Planck's constant is always used as evidence of the molecular nature of light. It is also proof of the fact that light as any wave can not have a length equal to zero and consequently the frequency equal to infinity.

[@lucishan5219]

Just what I been looking for! Thank you

[@lucishan5219]

Btw I had no issue with background, I thought it was a good mix

[@larrypeteet5575]

Thank you, well done and understandable!

[@Overunity357]

This is the greatest video i've ever seen. just. ever.

[@GlynWilliams1950]

Great video. Very clear explanation

[@daliabarrancoz9398]

Please make a video about DIY cavity for catch photons and get polaritons, now your channel is really a piece of gold

[@royrosales81]

Cool video, man. Nice work.

[@bennythejet5026]

The picture at 1:55 is absolutely fucking insane I love it

[@nosuchthing8]

Excellent.Million thumbs up.

[@Impatient_Ape]

An important detail for people who might be confused or unfamiliar with the jargon. That minimum mentioned around 1:30 in the video -- Planck's constant -- is not a minimum energy because it's not an energy at all. It has the same units as angular momentum. He deals with "h" correctly later though.

[@user-hk5ji5ws9d]

Great Video

[@papatrick1]

Nice man! i'm going to check in on the mondays :D

[@lachlanjackson70]

Well done!

[@kayapilat7829]

I did an experiment similar to this in lab for one of my intro physics courses. I wrote my first scientific paper for JAUPLI on that experiment.

[@oleksijm]

I will go against the flow and say that I enjoyed the music as well!Also, it is natural that it was only an approximation of the Planck's Constant that was found. After all, this is largely a DIY experiment to illustrate a point. Subscribed!

[@SenorAhole]

Nice work

[@varunnrao3276]

This is excellent

[@franknomustard]

Cool science video! Using cardboard scrap wood and electrical tape to measure plank's constant is just boss!

[@Mariocai]

Nice job!

[@LA_Viking]

Your video is spot on...measuring h isn’t easy. So if you went through that much bullshit to make a good, informative video, you’re serious about the subject matter. Subscribed.

[@svampebob007]

the interesting part going down to the fundamentals of the planks constant, which is based on the mass and time, but is also tied up to the space and time, who's also based on the planks constant.

[@michaelwhitaker4372]

Really nice demonstration. Thanks for taking the time to make these videos, scientific education is so important.

[@TheKritharth]

good explanation! measuring planck's constant IS a big deal!

[@slimsammyone]

Awesome video.

[@hsaqer007]

Hello mate, can you please tell us from where did u buy the diffraction grating? Thank you

[@Max-bz8ev]

We did this one in high-school physics class. I was kind of amazed the first time we tried it out, because we were effectively measuring a nanometer-range property, i. e. the wavelength, at great accuracy using only a light source and a grating.

[@caleb7799]

How the hell did you get so lucky to learn anything in high school?

[@Max-bz8ev]

@@caleb7799 where are you from? the school system in Germany has its flaws but it could be worse.

[@caleb7799]

Max the Atheist I guess it could be the American school system like ours 😞

[@Max-bz8ev]

@@caleb7799 I definitely haven't heard many good things about American high schools, especially public ones. that's super problematic because children of rich parents get another head start in addition to all the other advantages they already have.

[@caleb7799]

Max the Atheist they do, but this country does not value public education like it should.

[@kalsara001]

how to spot a genius? give someone a led and a ruler and he will figure out the Planck constant. such a nice experiment! good job mate.

[@Jobobn1998]

This is the first video I've seen from The Thought Emporium, and it really helped me understand exactly what Planck's Constant is! Thank you so much! Also, you definitely earned my Subscribe!

[@thethoughtemporium]

Glad you enjoyed :)

[@thatyougoon1785]

1:34 scishow said that he first combined to working approximations, one for low and one for high energies and only later found out that you get the same formula when the energie states are discrete.

[@godzillazumagod9146]

Thank you. I never seen it that way. Electron inertia is the cause of the ir radiation inside gas. Planks constant deals with this specific energy.

[@kirkhamandy]

great video but the backing music could do with being lower or not there at all, it adds nothing and distracts from your voice. just some feedback

[@Lyle-xc9pg]

exactly what i was thinking, i didnt want to listen to what he was saying and instead listen to the music

[@LMFAOdudeification]

Disagree. I like having background music, and it was rather comfortably in the background for me.

[@Sigmaairav]

Universal constants in themselves leave me with a bunch of questions: What are the mechanisms or properties of the universe that give these values to these discovered constants? Are there other constants out there waiting to be discovered? Are there properties of the universe that exist on scales smaller than we can currently measure that if/when we develop the tech to peer even smaller into the quantum realm; we will be able to discover, define, and measure them?

[@sciencestararvinsinghk]

i love your videos

[@Tim-Kaa]

Hi, when are you planning to do the new Plank's measurements experiment?

[@kyedo]

2 thumbs up, awesome video.

[@LucasArtCommunity]

How are you reading minimum voltage for a light emission? Human eye?

[@Oleksii.M]

Thnx for great videos! Whats name of music author?

[@oaktreebrannon7375]

The music didn't bother me at all. Cool video, thanks.

[@knowgnod]

Amazing video! Subbed right away...

[@thethoughtemporium]

Thanks :) glad you enjoyed

[@Mr.Unacceptable]

Well done I understood that. Not the math but the explanation of how it's calculated and why. Could you make the music background?

[@thethoughtemporium]

I've been getting mixed reactions about the music. When I'm editing it's very quiet, but it seems that on some speakers it's overpowering. I'll make it all a bit quieter next time. Glad you liked the video though :)

[@MMMM-sv1lk]

Great experiment/video... Was this the original experiment which scientists used to test their calculations of the planck's constant?

[@domesticterrorist483]

no as LEDs were not produced till the 60's. The photoelectric effect can be used to measure h but you need a super accurate ampmeter that can measure nanoamperes

[@victorguasch190]

Great video thanks. Just a humble comment: the semi-dramatic background music is totally unnecesary, in fact is a distrracting element.

[@SzTz100]

Impressive

[@kingofspades8856]

You're very smart!

[@nicolaslandeourtecho5396]

In the e*V = E equation, the V is the threshold voltage?

[@mcdudelydoo3116]

When measuring the wavelengths with the diffraction grating, does it matter what voltage is applied to the LED? Do the LEDs always emit a constant wavelength of light?

[@DFPercush]

tl;dr No, voltage doesn't matter, as long as it's above the minimum threshold and not high enough to blow the thing immediately. The wavelength of an LED can be affected by temperature. Otherwise it's determined by the chemistry of the semiconductor material. Voltage and current affect the intensity of light (number of photons per second), not the color directly, but of course, any electrical device produces heat when you pump more power through it, so in that way, it could affect it.

[@HighFidelityFox]

Very nice! I love Plankcs. Are you gonna update us on your P. MICROSPORA project?

[@thethoughtemporium]

Yup! We're getting a lot of the older projects started up again so we can finish them, so expect lots of part 2's in the near future.

[@lolsmcfee]

im excited to see part 2 of the transdermal stuff

[@slendy9600]

The Thought Emporium sweet. i cant wait to hear an update on your kombucha leather

[@lidarman2]

Interesting. It seems the error comes from the voltage because in order to get the correct energy for the red LED, the wavelength would have to be longer than 800 nm which is too long to see effectively. I would love to see the numbers if you just turn the LEDs on fully instead of when you just start seeing light.

[@shatterpointgames]

YESSSS I've been trying to grasp this, but unless you see how measurements are taken in real life and how the theory is applied it won't make sense. Thank you!

[@thethoughtemporium]

Happy to help :) I made this video for exactly that reason. There's a lot of hand waving in textbooks, but until you see it done, it just doesn't make sense

[@HenriFaust]

A reverse photoelectric effect. Clever.

[@v1sa9e]

whe calculating the constant using E*lambda over c, shouldnt the resulting number be in J*s instead of eV*s?

[@TheSam1902]

For small angles, tan θ ~= θ so you don’t have to compute the inverse tan. Anyway great work !

[@antoniozuniga9012]

Samuel Prevost define small, at 33° that isn't real

[@rydohg]

You are awesome! You deserve more subs

[@thethoughtemporium]

thanks :)

[@willwarden2603]

So all of those Sundog’s in my sun pictures are second order images not nibiru?

[@okay8632]

Nibiru is probably now what we know as the asteroid belt, maybe an interstellar war is responsible for it exploding, it would make sense, that belt is very difficult to explain otherwise.

[@moiquiregardevideo]

Nice explanation. Small detail: I like to see the color value in terahertz (frequency) instead of nanometer (wavelength). It is easier to mentally relate color vs voltage when the numerical value, the frequency, also increase. Beside, frequency never change from deep space vacuum to atmospheric air to any transparent liquid or solid, while wavelength is a moving target. The white LEDs need 3.0 volt because they are actually creating a specific frequency in the low uv range and a yellow fluorescent coating does convert the uv photons to one photon amongst a preselected set in the visible range: the carefully selected coating will appear "warm" by having a higher percentage of uv photons converted to red than green or blue. The term "energy" is still wrecking havoc in my brain. I have tendency to relate it to power, but I am used in electronic to never confuse tension in volt with power in watts. I know very well that current in amps is inseparable from voltage.

[@jimstanley_49]

Working in optics you will probably never see light described in terms of frequency. I've been working at an optical instrument manufacturer for four years and the only measurement that isn't in nanometers is in angstroms. I don't think any of our instruments or software will display frequency.

[@moiquiregardevideo]

@@jimstanley_49 you are right, I worked for a laser company for 8 years. I never read or heard frequency in terahertz. One German intern gave a talk about the femtosecond laser. His way of explaining the short pulse using Fourier analysis was much more clear than the usual explanation talking about group delay, the separation of color, etc Both method give the same answer somewhat like the particle theory and the pilot wave.

[@vixx328]

Oh thank you this has been bugging me for more than you know.

[@kavalkid1]

Music from Carman is so distracting, I turned it off. Music does not aid concentration. Not Mozart. Not any. The information is important. Please eliminate the music!

[@diaabnasir471]

Carmen is not Mozart 💀 It’s Bizet

[@shoam2103]

How'd you turn off the music and listen to the voice? 🤨🤔😯

[@venkatbabu186]

The frequency of any matter is one fourth the value of phi times radius. Matter content in event horizon is one fourth the size of black hole times phi.

[@operativexeight]

effing subbed!!! p.s. i didn't even notice the music until i scrolled down to the comments... sheesh people. chill.

[@WingDiamond]

Space Pirates make you walk the "Max Plank"!

[@jordanrandal5540]

At 6 minutes in your video you add an extra pair of images (green dots). I can't get those in my setup no matter what I try. Any suggestions? Getting higher order image pairs from a diffraction grating means a lot to me and my Dad. Please help.

[@thethoughtemporium]

I noticed the actual dots significantly further away than I presented it in the video, almost on the other wall. I'd try and aim at a screen much further away to start

[@jordanrandal5540]

We can't get that to work no matter what we try. Please make a video with higher order images and tell us how you did it. It would mean a lot to my Dad to know how to do this in his lifetime.

[@thethoughtemporium]

Just tried it to confirm. you're right it doesn't work. My first guess is that the diffraction grating has too many lines per mm and so the second order image is destroyed somehow. When I was in school we used an old school spectrophotometer that used an actual prism. I was able to actually see the second order image with that really easily, though it was much dimmer. Perhaps it just doesn't work with diffraction gratings. I'd try a prism or a different grating. I hope that helps. I don't have any other gratings on hand so I can't try. I honestly thing your best bet is a prism.

[@jordanrandal5540]

Thank you. Your reply means a lot to me. I will continue to try to make it work using a prism like you suggest.

[@jordanrandal5540]

By the way my Dad and I really like your video on how to measure Planck's constant. We are grateful for the time and effort you put into this video. A simple method for measuring Planck's constant is indeed the main point of your video. But the prospect of generating higher order images with a diffraction grating caught my Dad's attention. It would be very exciting to make it work. A video on Khan Academy seems to claim higher order images can be created with a diffraction grating. www.khanacademy.org/science/physics/light-waves/interference-of-light-waves/v/diffraction-grating

[@slappy8941]

It's crazy that horses, trains, and steam ships were the only modes of transportation when these questions were first asked, and here it is well over a century later, and we've got all this crazy technology, but we still haven't answered these questions. The genius of the early physicists is unbelievable.

[@justanotherguy469]

They have been answered, just hidden because it would give the world free energy and ant-gravity devices, which would render the banking and energy cartel useless. They are the ones who control the flow of information. Knowledge is power.

[@a.bergantini4129]

6:15 Maybe I am just stupid, but what is the "m" in the equation "d sin(theta) = m lambda"?

[@meetsandeepan]

i am just amazed how he casually stated ''just 12% off from the actual value''.

[@om-ni]

muchos gracia

[@user-ed7gm7ol8k]

you and cody (from codys lab) are my favorite youtubers. ı think you must make an collaboration.

[@noahegler9131]

I agree, but Cody annoys me. Not sure why.

[@kedityt]

Please make the next tutorial on how to use the tracking client to get satellite images!

[@thethoughtemporium]

I'm working on it, but it'll be a little while

[@ericthomas2675]

For the table with the wavelengths what were the respective colours for them?

[@jimstanley_49]

618nm is red 586nm is yellow 551nm is green 447nm is blue

[@robertnaegele9834]

Cool.

[@andreykhazhevskiy3230]

Energy in form of voltage?

[@gabrielgauchez9435]

that graph is confusing, you said this works good at low T but as you get to over a few hundereds degres the graph aprox infinity, but the arrow was changing wavelength not temperature

[@germyname]

Excellent video but probably should correct the partial Avogadro's number as identified by Erwt64.

[@kchorman]

6.626x10^-34 Js actually

[@ringocash6143]

what is the name of music in background 7:30

[@naziribrahim5154]

what was the maximum error in this experiment?

[@thrdel]

At 2:40 min you are trying to explain that the energy E of a photon as being equal to the frequency of the magnetic wave times Planck's constant , right ? I can only assume that you're talking about the frequency of the electro-magnetic wave that generated the photon. What about the situation when a single photon is generated by means other than electro-magnetic waves ? For instance , a radioactive atom decays by releasing an alpha or beta particle that in turn interacts with an electron , which in turn will release a photon. What frequency are we to use in the formula E = h f ? Also , light has a frequency , the photon does not. Light travels as a wave , how does a single photon travel ? Is it something based on the interaction between energy and space/time ?

[@dnomyarnostaw]

"Photon energy is the energy carried by a single photon. The amount of energy is directly proportional to the photon's electromagnetic frequency and inversely proportional to the wavelength. The higher the photon's frequency, the higher its energy. ... Photon energy is solely a function of the photon's wavelength." en.wikipedia.org/wiki/Photon_energy I read this as saying that even a single Photon has to have a frequency. ie it is a small wave.

[@RoboBoddicker]

Photons *are* electromagnetic waves. They aren't separate objects. A photon is just the minimum amount of energy an electromagnetic wave can exchange based on its frequency (with h being the constant ratio between that minimum energy per frequency). Because EM waves (and all other matter) can only exchange energy in minimum chunks, they behave like particles in certain regards, but they are not little billiards balls floating through space.

[@alchemy1]

So is this "h" The energy of one single wavelength of light of any size? That is what I want to know. You didn't say what "h:" is the measurement of? Minimum of energy of what?

[@arnold-pdev]

Heads up, for the white LED, you said it "gives a nice rainbow." In fact, if you look, you see three distinct images, roughly red, blue, and green. This is because white LEDs are in fact red, blue, and green LEDs in a ratio that appears white overall.

[@pezwarrior4]

What are time crystals?

[@SpotterVideo]

Quantum Entangled Twisted Tubules: When we draw a sine wave on a blackboard, we are representing spatial curvature. Does a photon transfer spatial curvature from one location to another? Wrap a piece of wire around a pencil and it can produce a 3D coil of wire, much like a spring. When viewed from the side it can look like a two-dimensional sine wave. You could coil the wire with either a right-hand twist, or with a left-hand twist. Could Planck's Constant be proportional to the twist cycles. A photon with a higher frequency has more energy. (More spatial curvature). What if gluons are actually made up of these twisted tubes which become entangled with other tubes to produce quarks. (In the same way twisted electrical extension cords can become entangled.) Therefore, the gluons are actually a part of the quarks. Mesons are made up of two entangled tubes (Quarks/Gluons), while protons and neutrons would be made up of three entangled tubes. (Quarks/Gluons) The "Color Force" would be related to the XYZ coordinates (orientation) of entanglement. "Asymptotic Freedom", and "flux tubes" make sense based on this concept. Neutrinos would be made up of a twisted torus (like a twisted donut) within this model. Gravity is a result of a very small curvature imbalance within atoms. (This is why the force of gravity is so small.) Instead of attempting to explain matter as "particles", this concept attempts to explain matter more in the manner of our current understanding of the space-time curvature of gravity. If an electron has qualities of both a particle and a wave, it cannot be either one. It must be something else. It must be something else. Therefore, a "particle" is actually a structure which stores spatial curvature.

[@andresrebata1958]

When u calculate wavelength, what is the "m" in the equation dsin (theta) = m× lambda? Thanks

[@thethoughtemporium]

Wave number. So which dot you're using. If you use the second order image you put a 2 there which you divide the other side by to account for the much larger angle.

[@andresrebata1958]

The Thought Emporium Oh! Cool! Thanks! Nice experiment! Quantum mechanics is awesome!

[@aniksamiurrahman6365]

Looking forward to see the spectrometer video.

[@necroorcen]

Lines in the diffraction grating are not prisms nor they act like a prism. Prisms use dispersion (property of materials), gratings use diffraction (property of waves). The effect is similar (decomposition of light spectrum) but this is not the same.

[@LutzSchafer]

Exactly. Moreover dispersion spectra are not linear as diffraction ones are. For the former you would not even be able to make this experiment so simple as you would need the materials refractive properties usually approximated by polynomials.

[@Terminator-od1ep]

h isn‘t 6.023*10^(-34) js, it‘s 6.626*10^(-34) js

[@YouthFreedomFighters]

If you want a really simple way of finding out Planck's Constant you could contact Suzie on ham radio and ask her, although she will want you to sing for her first.

[@BremsstrahlungChannel]

dude i love youre channel and enjoy every single video, but please ditch the elevator music ;) Very interesting topic however! :)