Quantum Physics - Part 1 (Blackbody radiation, Wien's Displacement Law, Planck's Law)
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- Опубліковано 28 чер 2024
- In 1900, Max Planck worked out the relationship between the radiation emitted by a blackbody as a function of temperature and wavelength, and in doing so started a whole new branch of physics.
0:00 - Intro
0:47 - What is a blackbody?
1:26 - Radiation and temperature
2:27 - How the experiment worked, the Stefan-Boltzmann Law
3:58 - Wien's Displacement Law and the relationship b/w temperature and wavelength
5:12 - Rayleigh-Jeans Law and Wien's Distribution, why they didn't work
6:51 - How Planck derived his Law
8:22 - Energy is discrete, not continuous
9:36 - Review
In reality, the equation Planck came up with was much more complicated since it involved Intensity as a function of two variables, but we are focusing on the idea that energy had to be a discrete value instead of any value as was previously thought.
Well done! The historical overview combined with the basic mathematics is spot on. I will show this to my class tomorrow.
Omg!! I was so shocked to see this only got a few views! I'm definitely going to watch more of this though! I hope your channel grows really well :)
This is one of those those great but largely undiscovered nuggets that not only explains the subject of blackbody radiation in detail but also, importantly, the historical context of the research, the questions being asked about the relation between frequency and temperature, and the steps that led to a solution.
I've been trying to comprehend blackbody radiation for a few now and this is the first video that got it to click. Thanks!
This is honestly one of the best explanations ive ever heard
Planck's approach was to analyze the entropy of blackbody radiation as a function of energy. To make both high-frequency and low-frequency data consistent with the Second Law of Thermodynamics, he included an additional "guess" term proportional to the frequency. Planck's application of Boltzmann's Statistical Mechanics led to his conclusion that the material of the walls emit and absorb radiation in discrete quanta.
A paper titled "Planck’s Route to the Black Body Radiation Formula and Quantization" by Michael Fowler (7/25/08) gives a nice discussion.
I'm still in the weeds, but that presentation got me much closer -kudos to you, sir!
Teachers like him makes physics very interestinng 😊
Thank you so much for including the history as well, I rarely find such high level lectures incorporating information in an interesting narrative! Subscribed!
Excellent explanations. The demos helped a lot too. Thank you!
Extremely well done! Nice presentation. Thank you.
The best video I've encountered about this topic, I understood the topic more. Thanks
excelent, you show the problem and how scientists asked questions to come up with the current solutions. well done.
dude, this made me understand the concept so well, I was so lost in my college class
thank you so much you made things so much simpler for me
Fantastic work. You're a natural born teacher. Thanks for this.
This is amazing! Thank you for the great explanation!
You explained this the best I've seen.
Wow really helped supplement both my professors lecture and even my reading of my textbook! Thank You!!
Such a critical piece of the puzzle! Great job! 😀
Great video--added significantly to the discussion!
Man bless you for creating this .. I finally grasped this concept
My 2 hour lecture in 10mins thanks sir 😁
Excellent video on the subject 🍻
Thank you! Very interesting and educating video.
Loved this video, thank you for the explanation
Good video, very enjoyable to watch and informative ❤💪
Brilliant presentation!
Great explanation. Thanks.
Outstanding explanation sir,u really explained in such a great way that made this most confused topic very interesting and very easy .I am ever grateful to you.thankyou so much sir,for explaining this topic in a clear and best way .keep doing more videos like this ,it will be very very helpful to us.All the best sir,u should reach heights❤
What a great video, keep it up!!!!!!
Thanks A lot Man! I really love this content and Now Imma satisfied. 😀
Brilliant teacher. U made my day!
This is amazing ! Thanks alot
Thankyou Sir I found it more like a interesting conversation .🙂
Very nice insight! Thanks.
This is great actually great
I am already in quantum physics and this is best physics teacher on UA-cam
Wow great job... keep it up
Yo homie is absolutely goated.
BAM! Thank You! I couldn't comprehend get how Plank decided to use Energy as discrete units ! omg! I've been wondering that for yrs. yrs!
Wow
Well explained
very helpful thanks😃
Thank you sir you r very underrated
Thank you!
Sooooo underated!!!
Love the graphics (are you drawing everything backwards?) Really good simple explanation and use of equations
Brilliant more please
Probably not. He can just invert the digital screen he is writing on.
Thanks, yea I write on a clear sheet of plexiglas and just flip the image with a video editor
This man> my college staff with phd's
Thanks. Love from India
Amazing
Unbelievable. How you explain this concept so easily??? It's great. Today I gain more knowledge of this topic. Thanks a lot. 🙏
Nice
Nice actually...
Dude, you just made a boring science lecture, very interesting, Thanks
Thanks
very nice video. How the Planck ypothesis explains the Ultraviolet Catastrophe ? I mean why the fact that emitted radiation has energy E= nhf, leads us to predict the actual distribution of the black body radiation at all wavelengths? Why most of the emitted energy is located at a small area of the spectrum?
So I understanding that the energy comes in packets. But why does that make the curve go back down eventually? I don’t understand that yet
Planck constant is energy in one photon. Multiply this by number of photons per second and you get the energy of a radiation based on frequency or color of the radiation.
Very clear explanation. But why are the curves shown smooth? Is it that there are so many frequencies thaat they appear smooth but if we had better definition we would see little spaces between the points?
yea that's exactly it, we just use a smooth curve to represent it since there's so many different possibilities for frequency (a lot, but not infinite). If you zoomed in on the x-axis you would see discrete quantities
Great video, thanks, but how exactly proposing energy is quantized is fixing the curve in high frequency region?
allowing energy to come in discrete amounts instead of any value made the mathematical model match the curve that was seen in experiments
@@PhysicsOMG The bit I struggle with is (as Fairboy says) - h fixes the curve, but why? I wish someone could explain what is happening as we move along the curve, why does it come back down?
Love frm India
👍
So Boltzmann was the creator of the idea of energy quantization!
hey that was a very nice video. Im a high school physics student and some questions I have are:
-why do the intensities of wavelengths lower than the peak value decrease so quickly as compared to the curve for the wavelengths higher than the peak value?
-does the black body radiation curve mean that it cannot be applied to objects that are not good absorbers of radiation, e.g. plastic?
Thank you if you answer these questions
Thank you, I'm glad it helped! For your first question, remember that the smaller wavelengths (which drop off quickly) correspond to higher energy photons. If you have an object at a certain temperature, there is only so much energy that can be radiated (no UV catastrophe). So there can't be very many of these high energy photons because statistically it is more likely for the low energy ones to be given off. That's why the low energy end of the spectrum gradually trails off but the high energy one drops off quickly - the probability of high energy photons becomes basically 0 beyond that peak. There is a really good minutephysics video that explains why its mostly lower energy photons that get emitted: ua-cam.com/video/i1TVZIBj7UA/v-deo.html
For the second question: in real life the only things we see that actually behave like true blackbodies are ones we make (like the example of an oven with a hole punched in it), or stars. Everything else will sort of follow that curve but will only have a fraction of the ideal emission seen in a blackbody curve. So yes, something that is a poor emitter will not have an emission curve that looks like a perfect blackbody curve.
@@PhysicsOMG thanks a lot
in 03:59 he says maximum or the peak wave lenght but if the wavelenght is plotted along x axis shouldn't the peak wavelenght be at infinity (according to the graph)? or should it be peak intensity ?
By peak wavelength we mean the wavelength that corresponds to the peak in the graph. That shows us the most common wavelength of photon that is emitted by the blackbody.
@@PhysicsOMG thank you
Please tell me how you do the whiteboard thing its the exact setuo as Joel Speranza and hes keeping the secret safe. My final physics exam for 50% is tomorrow morning but this is the most important thing right now.
lol it's pretty easy, I set up a camera in front of me, I sit behind the board and write. In the original video, all the writing looks backwards but when you mirror the image it comes out right. You can tell because I'm right handed but it looks like I'm writing with my left hand in the videos
@@PhysicsOMG thank you i thought this was the case. Physics was easiest exam ever although I forgot a few formulas and wrote wrong ones down lol it happens
Thanks for the video. I am trying hard to understand this topic. To me, E=nhf just means that energy is a function of frequency and does not imply discreteness since presumably f can vary. Or is the point that for a *given frequency* energy can only be positive integer multiples of hf? How is frequency allowed to vary? Is frequency also quantised somehow?
Frequency is continuous and can be any value you want. But for a given frequency, the light is actually emitted in little chunks that are a multiple of Planck's constant instead of one big wave. It's not the value of the energy itself, but the wave packets that carry away the energy that are quantized.
@@PhysicsOMG Thank you for that clarification. I really like your explanations. I am still a bit confused though. If energy is quantised, then it stands to reason that the energy that you put into your black box to heat it up is also quantised. And therefore only certain frequencies will ever be input or emitted. Where does the continuous spectrum of frequency come from? There's something missing from this picture, at least to me :)
Dear Professor,
Max Planck constant is the smallest unit in nature.
how can it be that h/2pi is even be smaller?
the Planck length is the smallest possible size of something, but h/2pi is the uncertainty in a measurement
@@PhysicsOMG Thank you so much. Your answer is very interesting my dear professor.
someone else said the following?
Planck's constant is, indeed, the smallest constant used in physics, which is reflective of the quantum scale. However, it is just a scale and not a physical quantity. Hope that clarifies it.
please could you give your opinion on this ?
how do you write backwards that well?
虽然没听懂但是谢谢🥺
wouldnt the peak wavelength be inversely proportional to the temperature in wiens diplacemnt?
yep, thats right
I think it should be the intensity (I) = sigma T^(4) cuz I=P/A 😅
Is anyone going to talk about how this man drew a graph and wrote letters backwards??
James Jean was not french, he was English, I don't think he pronounced his name like that :D
lol I know, one of my professors in college pronounced it that way so that's how I learned it. Old habits die hard.
"peak wavelength"? do you mean wavelength at peak intensity?
yes
I think "Jeans" is pronounced in English and not French? He was an English physicist I thought? James Jeans is his full name. thanks
5:38 won't it be because the black body will end up giving all its energy as radiation and have infinite heat capacity?
yea, basically if that model was correct then the object would emit infinite energy at smaller wavelengths and do all sorts of other insane stuff they knew must be wrong
Maybe infinite in this riddle makes the black⚫ night sky☁ turn blue in the daytime. If not, then it's something to imagine a dazzling sun ☀️ against a black⚫ background of the night 🌃sky which would behave like the black body.
Power of infinity.
SHREKK !!
Sir your looking so handsome and your teaching is very welll aalso
Is it pronounced as plahnk or plunk?
I'm not German so I'm no authority on it but I think it's plahnk. I just say it the same way my physics teacher always said it when I was in high school.
@@PhysicsOMG thanks for the reply : )
Another formula can not Show this
Butful
Very poorly explained
Thanks