What is a Black Body? (Stefan Boltzmann's Law, emissivity, grey and white bodies...) - Physics
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- เผยแพร่เมื่อ 5 มิ.ย. 2024
- A black body absorbs all light that is incident to its surface, but more importantly, when it has temperature, it emits light under the form of black body radiation.
In this video, we discuss the process in which a black body absorbs light, gains energy, and thus can re-emit it (under the form of… light). A great example being the Earth receiving light from the sun and remitting infra-red radiation.
We also discuss how a black body emits light when it has temperature, and why. This will bring us to Stefan Boltzmann’s Law that associate a luminosity (or power) to a temperature.
Real object are not black bodies but their behaviour can be more or less close. This idea is related to the concept of emissivity. This will let us introduce the ideas of grey and white bodies.
The black body model is used in many areas of Physics, like for example astrophysics, thermal physics and materials sciences. So it is essential to have an understanding of it to enjoy the multiple wonders that lie within these areas of physics.
The black body description in this video is based on classical physics theories.
Content of this video:
0:00 What is a black body?
0:30 The nature of light (Classical description)
1:21 Interaction of light with a black body
2:48 Emission of light by a black body
3:55 Stefan Boltzmann’s Law
4:35 Grey Bodies
4:50 What is emissivity?
5:31 Examples of grey and white bodies in the real world
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Credit:
Background that starts at 7 minutes and 33 seconds: Traverse galaxy Background: by F. Summers, G. Bacon (STScI). Simulation by C Hummels, P. Hopkins (CalTech) and A. Wetzel (UC Davis)
All other illustrations that are not credited in the video itself are by Edouard Reny or from the public domain.
Music by Edouard Reny.
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This video is produced and presented by Edouard Reny, Ph.D. in solid state chemistry and private tutor in Physical Sciences.
For access to great resources that will help you with your studies of high school Physics (IB Physics, A Level Physics etc.), visit the "Physics Made Easy" website:
www.physics-made-easy.com/
Edouard provides one-on-one private tuition in Physics (face to face or by Skype). If you wish to contact him, visit his website: www.physics-tutor.nl/
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Einstein? Maybe not. Amazing teacher? Thank you :-)
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Thank you very much Irene for your very kind feedback.
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Bravo Sir! You really have a gift for teaching physics. I found this so incredibly helpful. Blackbody can be confusing but you made it make sense. Thank you so much for all the time you spend making these videos!
Thank you Jayron for your very kind words. I am glad that that my video clarified blackbodies for you. :-)
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Thank you for your kind words!
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Hello Nimisha, thank you very much for the kind words, and recognition for the effort I put in scripting, shooting and editing these videos! It's really worth it: my goal as a teacher is to open young minds to the true amazement that Physics provides, and all the feedback I get from online and real life students shows me it works. When you dig a little, reality is more stunning than fiction and that, by far !
I checked your channel, your english is amazing! I have a few Indian friends and I never heard a native Indian pronounce English with such a clear accent (you are more intelligible than I am, and English is one of my mother tongues). Congrats.
@@PhysicsMadeEasy you’re very welcome! Assume you saw one of my stand up comedy videos. Hope it was entertaining, thank you for checking out. Will continue to give feedback and comment as I watch these.
Wow this was the simplest most understanding explanation
Hello Maeva, thanks. I am glad my work help you improve your understanding
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Thank you for your kind words!
Thank you very much Mr. I am currently at grade 12 and I didn't even know why humans emit infrared radiation. Thank you very much. Muchas Graćias!
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Hi Jeremy, wow, thanks for your feedback! I am glad you enjoyed the video. Be well!
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Merci for your kind words Kanakarajan :-)
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Wow, thank you for the feedback. If it is true, then, you just realized that Physics can be pretty cool. I encourage you to explore deeper!
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Thank you Nikhil. I am glad you find my content useful. "Positively impacting young budding minds" is the one of the aims of this channel: to show them that Physics is not that difficult, by explaining stuff that can allow them to make sense of what they are taught in the classroom.
Sir, Your videos have made Physics Easy for real. It has made the journey in the subject much more fascinating. Really looking forward to learning more physics through your tutorials :)
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I have watched so many videos and this video finally made emissivity click for me! Thank you so much!
Hello Lindsey, I love that when a student tells me I unlocked an understanding. Thank you so much for your feedback. ♥♥♥
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You are warmly welcome. I am happy that I could clarify things for you.
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Thank you for your support Asadrauf ❤️!
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Thank you Muzeem, I am glad you enjoyed the Video. I am always amazed by the elistism of some text books, that keep notions like the electric potental misty for the high school student, while in the end this notion is actually quite easy to understand!
this is truly an amazing video!! thank you for your excellent teaching
You are welcome Venus. I hope my work was useful to you.
Thank you! ! What a master of explainer!!
Grateful thanks Sir, for very clarifying presentation of the BG ery grey concept.
You are welcome :-)
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That's the whole point ;-)
I kept seeing the same stale, cookie-cutterunhelpful descriptions of a "blackbody" until I found this video. Now I understand what it is, and what the point of it is. Thank you!
Thank you for your feedback Stephanie. I am glad you found that my approach kind of got above the "noise". And even more glad that it brought you an understanding. Be well.
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Thank you for your kind feedback :-)
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Hello Indu, that's the point of the channel, to make Physics easy (and clear)! Thx for your feedback.
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You are welcome, I am glad I could lift your confusions :-)!
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You are welcome Anjali
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Thank you Chris, dive a little and one discovers how Physics is awesome (when I begin with my students, they hate it, and when we part, they can't get enough of it. Some even decide to make it their field of study and enroll in a physics curriculum at University!)
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Thank you Shopper, I am glad I could help ;-)
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Hi Scrayla. I am glad I was able to help you with your studies! Thx for letting me know, it encourages me!
I think this class is very helpful for Stefan Boltzmann low
Hi Monika, I am glad you found my work helpful. Thanks for letting me know!
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Hello Roseanne,
On Internet, you shouldn't consider that something is legit based on an accent! But thank you for your kind words :-)
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I Isabel, I am glad my work helped you :-)
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Thank you so much ,sir.
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Many Thanks :)
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You are welcome Danella. I am glad my work helped!
I wish i could have teacher like you so the world can have another Einstein
Thank you Mr Gammer! You believe you have the potential to become another Einstein... haha! Maybe.
I was really bad in physics in high school because of the lack of quality of the teacher's pedagogy. I mean really bad: I came very close to quit school. I held on , got the minimal mark to pass the high school final exams. Luckily, during the two first years of at Uni, I met amazingly good teachers which made me realise that Physics was actually not that difficult. And my grades exploded, and I went beyond the PhD (post doc), always getting honors on the way.
That near-miss I experienced: this is why I became a teacher :-).
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Maybe not Plank, that would be a little arrogant haha! But thanks!
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You are welcome Kim, I am glad this video helped :-)
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Hello Karnati, thank you for your kind words. And I am glad you enjoyed my work.
Thankyou so much.
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Hello Zakir, Plasmon Resonance is an interesting phenomena, thank you for the suggestion. It might be a little too specific for this channel focused on clarifying the basics of physics, so that viewers can fly with their own wings, but I will think about it.
Good job professor
Thanks!
I'm hear to understand the physics of climate change. Stefan Boltzmann's law is an important law at the center of this.
Absolutely Kiren, The Earth is a black body at a temperature such that it emits its radiative energy in the Infra red region. This infrared radiation is what allows some of the bonds in molecules like CO2, H2O, CH4 to enter resonance (the IR is absorbed). This oscillation of the bonds generate the same IR radiation emitted in all directions, including back on Earth... heating the earth a little more.
First- I found this video very useful and interesting, thank you very much!
Second- I have a question: if I have two bodies floated in a high vacuum environment at room temperature while one body is heated in purpose to 100celcius and the second body should remain at room temperature. is it correct to coat the heated body with a black coating and the second body with silver
ickel coating?
You mean to keep it that way once the bodies are in that state: You heat one body at 100C, and the other one at room temperature. Put them in the same isolated box under vacuum, and you want them to keep their temperatures. Right?
Yes, I believe that would be the way to go. The inner sides of the container you put them in should also be coated with the silver coating.
Thank you ❤️
Thank you Hasti
Can't add this to physics playlist so I'll comment instead
Ha... I checked, there are no specific restriction on this video ( I just checked). Can you add other videos (from me or other creators)? Still, I am glad you liked it enough to keep it under the hood! thx for letting me know!
Thank you🙏
You are welcome Callum
Finally I got what black body means!! Thank you so much sir!!!
Bonjour Nicole, I am really glad to read this and that my work helped! :-)
Good video, it has an easy english for no-speaking english people like me
Thanks for your words Tower. This is also why I hard subtitle all my videos (hours of work!)