In the past few months, this channel has blown away most of the things I thought I knew about how light works. And quantum mechanics. And relativity. Most valuable patreon investment I've ever made.
Really? I asked my teachers these things so much they would get angry. This question i asked her and was not satisfied at all. This helped me but after 7 yrs🤣🤣🤣
Since the academic year’s done, I didn’t want my grandsons to stop learning. They complained about watching science videos, until they watched yours. They love your content and how it’s presented (seriously, who doesn’t love graphic representations, clones and squirrels?). For four, seven and nine year-olds to enjoy science is a feat unto itself. Your videos are entertaining and definitely informative. Please continue making videos! Thank you.
It's cool how lots of stuff ends being the same thing if you look deep enough -- it means there're all things unexpected relationships just waiting to be found! That's a large part of what makes me love math and physics so much.
"The mirror-like reflection in this is from the surface atoms. The color is from the layers underneath." This exhibits an interesting difference between colored metal and polished materials. Plastic, ceramic, and all kinds of other materials will have a diffuse reflection that we identify as the "color" of the material. But the mirror-like reflection is usually neutral. Shine a blue laser on a yellow ceramic plate, and you'll get a good specular reflection of the blue light but poor diffuse reflection. Repeat the same experiment with polished gold, and both the specular and diffuse reflection will be poor. The divergence between specular and diffuse behavior drives our perception of "metallic" vs. "shiny". And the material doesn't have to have a mirror-like finish to exhibit this difference. Some "brushed" gold will still have a very color-biased specular reflection compared to "brushed" yellow plastic. This comes up in 3D modeling, where you can typically set a material's diffuse and specular "colors" separately. For non-metallic items, the specular color is usually set to a neutral shade of gray. For metallic items, the specular color is the same as the color we associate that material with. Though sometimes the color is modified slightly to mimic the way our eyes and real cameras would process it. Of course, when I'm modeling something, they're just values I set without wondering how they work in the real world. As always, this video was very.... illuminating.
I'd understood that the metal with a single outer electron gives a specular reflection with formation of a virtual image. White porcelain with multiple electrons in it's crystalline surface reflects white with no virtual image, even though it's surface is more smooth. This video makes the point very clear. The blue laser seems too bright and too narrow a frequency range.
@@solapowsj25 polished porcelain will reflect a virtual image, but only by a minority of the light. The rest of the light penetrates deeper, where it is absorbed (if dark porcelain) or diffuse-reflected (if brighter). You can see your reflection in a well-polished piece of dark stoneware.
It's also why in PBR (physically based rendering), there are so many property maps for example for specularity and metalness. This video made me realise how that connected in the real world. I think the whole idea of PBR is amazing as it makes it possible to measure a surface property and then simulate it, creating a realistic result.
@@nimmen Another cool rendering feature I only recently learned about is taking a 360 degree HDR image in a real environment, and then use that image to set all of the lighting for a scene. There's even a polished metal sphere that filmmakers use to grab a quick environment map that will be used to light a 3D model in its place. This way, the light map can be updated with dynamic scene elements, and the ball is sometimes moved around while shooting as well.
@@solapowsj25 The thing about metals with a “single outer electron” is that it is a loosely bound electron that all atoms basically share. This is called the conduction band as it requires very little electrical potential to move electrons from one atom to the next. This creates more like a “sea” of free floating electrons. This “sea” has a very high degree of freedom in the plane parallel to the metal’s surface which means any light that is absorbed will move the sea parallel to the surface of the metal far easier than moving it toward or away from the atom. This is most likely why reflected light is polarized parallel to the surface of the material. I would also imagine that this high degree of freedom is also what allows the conduction band electrons to absorb most of the incident light as opposed to insulators absorbing a small portion.
I always wondered about it but now came to know conductivity and reflection are so much connected, You Surprise me every time thank you for your efforts.
I got a similar surprise while studying electromagnetism... the relative permeability and relative permittivity of a material have a direct relation with the refractive index of the material.
Yes, conduction requires there be only one electron in the outer orbital. The stable state of two electrons alternates with one electron during electron-wave passage in current flow. These materials do not allow light to penetrate deep as crystals, plastics and ceramics do. They reflect at the surface with least distortion.
Good video. 2 things though from someone "in the industry." 1), with the actual cost of material (incremental cost) because so little is used, Al and Ag are fairly irrelevant.The primary reason Al is often used instead is because of long term durability. Indeed the price to protect the Ag is more expensive (development and advertising and such) than the actual Ag! And 2, I think that green color at deep reflection may be coming from the typical soda lime glass used in second surface mirrors.
Wow, this was much more complex than I thought, but still you managed to explain it really well! I remember learning in school about mirrors being smooth while normal materials are rugged, but that wasn't the only part in the equation!
That was like my whole subtopic of mirror optics in 10 mins for my HS level. You even added some great explanation from graduation level as well Totally loved it. Thanks a lot it really helps my studies and feeds my curiosity. I just can't thank you enough.
Can you explain physically what is happening with the penetration depth? Why does electrical conductivity of the material determine penetration depth? Does that have something to do with the band energies in conductors vs insulators causing differing resonant absorption patterns? Also why does having a low penetration depth imply more of the light is reflected?
Love your channel! About 15 seconds in, I was thinking "Feynman diagrams would be a cool way to give an intuitive explanation". Get your bongos out! :) haha! Also, your point about green light aligned with something I was telling my eldest about why chloroplasts reflect green light (why are plants green?) because it is the most inefficient wavelength for absorbing energy for photosynthesis...it's no coincidence that plants and recursive mirrors reflect green!
In computer graphics we use probability distributions to model how light interacts with different surfaces. We call them BRDFs. My white material always looked a little too glossy, like satin or something... because it doesn't account for the depth and extinction parameters you were talking about! Thanks for the deeper understanding
For the reflection to match the color of the object, yes, you are correct.... but I wouldn't have any problem calling a smooth polished plate of gold "a mirror."
I love this explanation! I would have liked to see you explaining the result of electric conductivity in regards to the fresnel effect in metals an dielectrics, but this would have been too much. Love it! Even though this is two years old, I wanted to praise you for your videos!
I had a vague understanding of this ahead of the video, now replaced with the "nice, thank you very much" I so often have after watching. The way you make this approachable casts some light on other things (like the ocean's total internal reflection angle) and fosters further study -- and that's pretty awesome. I hope your subscriber count keeps going in the right direction :)
Hi, you are very kind to us all e you are the best teacher I know, I am a physics teacher and I didn't learn this things at the university. Amazing work. Perfect. It's a pleasure to help you on Patreon. Feel comfortable to take a rest when you need. We're here for you!
"So why aren't all insulators transparent?" By the end, it made sense why a good mirror needs to have a specular surface (that's the one most people discuss), why it needs to be a decent conductor (shallow penetration depth that results in greater reflected light than transmitted light), and not have electron energy levels that match the frequency of incoming light (resonate absorption traps light as heat, whereas dissipative absorption allows it to be released as EM wave patterns that can build up at the angle of reflection)....but I feel like that one question thrown in there wasn't answered. Am I missing something? What causes insulators to be opaque? is that simply a result of the random way the atoms are organized inside that produces constant absorption and emission internally? Does this mean opaque insulators capture more heat as a result if the continued oscillations of these atoms and increased kinetic energy from those oscillations? If not, why doesn't this transmitted light come out the other side of opaque insulators? (Sorry I know this is a long comment but I love your channel and your videos are so enlightening - just trying to wrap my mind around that piece)
Dont make your mind up too soon. Give all of physics a try and see where it goes. Thoretical stuff is really dry, though sometimes really exciting and mind blowing. Nowadays theoretical physics is really advanced and the experimentalists cant really keep up with all the stuff proposed. So the theorists dont get enougth imput back, as it seems to me at least. Anyways... Keep your mind open and question everything. :) I ll study physics soon as well and will by great chance be an experimentalist. Have a nice day!
(Was looking for the color of gold because of SR questions. Don't see them. But .. it's unbelievable how many comments you answer.👍 I don't think any other youtuber does that.)
@@ScienceAsylum Didn't get a notification again .. someone is hacking me 👀.. 👁 you! .. 😉. Jk, but I wanted to ask you. (Hopefully I don't ask too much.) You sometimes refer to brilliant.com. I am wondering .. can you learn physics there at "master degree level"?
Brilliant teaches a lot of things to their users and it's great practice. Some of it could be considered masters level material, but most of it is bachelors level. *To be clear though:* No online service could _ever_ replace an actual degree.
The surface of paper is not only rough, it's more like a fuzzy blanket or an air filter. The filaments of paper go every which direction, but are smashed down so overall it's a "flat" sheet.
Hey Science Asylum, another great video as always! As you know, we use the index of refraction in fiber optics, basically the backbone of all telecommunications. However, in my industry the “last mile” is usually coaxial cable, RF over coax. For the longest time, since the 1960’s, the manufacturer of the coax has specified the Velocity of Propagation of the cable, which is the percentage of the speed of light that the signal can travel through the cable. Well, nowadays this is actually very important for everything to work correctly (TDMA for example). So here is my question: The VoP is just a number from the manufacturer via quality control testing. Our servers work with each individual customer modem to negotiate the proper timing required to use ATDMA for that specific distance of coax, never actually solving for the VoP. We can use the VoP to detect echos of signal and get a pretty good idea of where a flaw or crack in the cable is located (within 40 feet) and repair these before corrosion sets in and the signal gets seriously impaired. Yet, as I understand it, there is no physics method to precisely derive the actual Velocity of Propagation of a RF signal through a medium. Are you willing to do a video on Velocity of Propagation of RF through a dielectric? Pleeeeeeeeeeeease.
There are a lot of things in physics/engineering that are much easier to experimentally measure than theoretically predict. The refractive index (mentioned in this video) is a good example. While we _could_ derive it theoretically if we could get a computer to model the behavior of light properly in the material, I don't think anyone ever _has_ done it. It's just not worth the trouble.
See if I understand correctly: a red object, for example, is red, because its electrons absorbed the other colors by resonant absorption, while the electrons (or the atom as a whole) absorbed the red light by dissipative absorption. Thanks, your videos are great!
I’m gonna have to be that guy and ask: “WHY does higher conductivity mean a lower penetration deapth” And great video as always, made me ask myself a ton of questions, which is always a good thing🙂
I do a lot of research and keep learning. Unfortunately, many professors stop learning after they get their degrees. (As someone with a chronic illness, I can tell you this is true of many doctors too.)
I was looking for a comprehensive explanation of why light is "bending" when crossing between 2 different mediums for years. This helped me a lot. Thank you.
Whoa.... I didn't think being a mirror would have so many properties of its own. This video was phenomenal!!! Understood each and everything clearly...! Thank you Nick!
I believe cellulose polymer in paper is actually spectacularly transparent, not quite as transparent as glass but in the grand scheme of things not too far off either. The diffuse reflection occurs purely due to the shape that the nature delivers it in, hollow squiggly ragged tubes with a lot of semi-regular partitions, so a lot of boundaries at which the light can exit or get reflected. People have used this property to make "transparent wood" and wet t-shirt contests.
You should cover fluorescence and photon tunneling in some butterflies' wings... they amplify colours by converting wavelegths to the visible part of tge spectrum, and redirecting photons which would otherwise be absorbed by ir lass through the wing.
Me before watching the video: I know why white materials aren't mirrors, it's because of the imperfections on the surface! Also me 1 second later: .....that's not the whole story, is it?
I have a lot of questions: 1. Why do we need to have low penetration depth. If something reflects 95% light specularly and the rest of the light just goes in somewhere, I have a pretty good mirror. Don't I? 2. How does low penetration depth translate to metallic luster. 3. Why conductivity is related to penetration depth in the first place? 4. If only resonant absorption can actually contribute to the internal energy of the material and dissipative absorption cannot. When the intensity of light drops of exponentially where does that energy go? 5. Related to 4. If different things reflect and transmit different wavelengths differently and that light gets absorbed. Why doesn't it heat up the material?. 6. If I have a lot of infra red photon and if it cannot be absorbed through resonant absorption, will they never be able to heat up the material? Or infra red photons are bound to be absorbed due to alot bands really close to each other at higher levels or the vibrational or rotational bands play a role. I have read about them but don't understand it. 7. How does the energy absorbed by resonant absorption gets transmitted to other atoms. Isn't it bound to the kinetic energy and potential energy of electron? 8. If I have 156.5 cubic meter of glass. It won't be tranparent, right? Or do I need to mutliply that to five too. Like a km or something. Does it mean that if I am within reasonable penetration depth. Everything would be transparent? I have had these questions for a long time. My teachers couldn't answer them. Now, I have more. Please, Nick, let me understand all of this once and for all. Possibly with a dedicated video 🙏
1. If your penetration depth isn't small, then it _wont_ reflect 95% of the light. 2. Low penetration depth mean less scattering. 3. Light is an electromagnetic wave, so it's interaction with a material is governed by how that material interacts with the field. 4. I didn't mean to imply that dissipative absorption couldn't contribute to the internal energy of the material. It can. Just not _nearly as much_ as resonant absorption. In science, there are very few clear lines we can draw. Most things are on a spectrum and absorption is no exception. 5. Material can only be heated by light they absorb and don't let go of. If the light is reflected or completely transmitted out the other side, then the material didn't keep the energy. 6. See my answer to 4. 7. No, the electron loses it and falls back to the lower energy state. It's just that the energy didn't get emitted as a visible photon. It became heat instead. 8. That would obey the same percentage rules as the mirror, so you'd need it to be about 780 meters thick before the intensity would get down to 1%. Yes, if you make _anything_ thin enough, it will be transparent... even a sheet of metal. That's exactly how Rutherford did his gold foil experiment. He made the gold sheet so thin that it became transparent.
Thank you so much Nick, some of them were obivous, but clarify this too: 7. When the electron falls, does it do smaller successive jumps and produces infra-red photons. Because shouldn't the photon that was absorbed should come out too. What I wanna know is how is it converted to heat? 5. The point was if all materials who are not white keep some light in. Why don't they just heat up?
7. No light is emitted from the quantum drop. The infrared light you're talking about is emitted because of atomic collisions, not for any quantum reasons. 5. If an object is a color other than white, then it _will_ heat up. Even white things aren't perfectly white, so they heat up too. Eventually, they'll reach an equilibrium with their surroundings though where they're emitting heat as much as they absorb it. At that point, they'll stop getting any hotter.
I have a question. Does dissipative absorption result in the frequency of light (colour to us) of an object given off or the reflected light of a mirror? p.s this channel has really inspired me a lot so thank you.
Yes, dissipative absorption is the kind that result in the color we see on objects. The colors (frequencies) near the resonance stay absorbed and the rest are re-transmitted dissipatively.
Thanks for valuing my work so much. I kind of have a niche style though. My guess is that I'm already at the sub level that style allows for. It's fine though. I'm comfortable with it.
Fantastic video! This is the best summary of reflection, refraction and transmission explained all together that I've ever seen. Normally these are presented as separate things but they're really all part of the same process. How does the photoelectric effect arise from these?
The photoelectric effect arises when the photon energy (usually at least UV) matches the gap between the valence and conduction bands in the solid. Electrons in the valence band of a solid (usually a semi-conductor) can jump up to the conduction band (or sometimes even free themselves from the solid all together).
"Conservation of energy shall not be violated!" Lol. The way you say that always cracks me up! Don't forget about Noether's theorem. That video was so interesting. I remember my physics book specifically said that scientists had _never_ found any violation of the conservation of energy, which prompted me to immediately write in the margin that that's actually not true because of Noether's theorem, remembering your video. Anyway, not criticizing this video in any way. For all practical purposes, I know energy of a closed system is conserved, so it makes sense to treat it that way. I just like seeing all the connections between your many different videos and math and physics concepts in general. Finding those connections makes everything more interesting.
Right, it takes a lot more extreme circumstances than some light interacting with matter to violate the conservation of energy. As for your textbook, it's standard procedure to lie a little bit to intro students. I'm not saying I agree with it, but I'm not surprised your textbook does it.
Hey Nick, great video as always. But is there a chance you could do a video related to nuclear physics? Why is the nucleus so special? What is alpha and beta decay?
Oooooooooooooh, wow! Thank you! The refractive index of light going through different mediums has baffled me for decades! Up to now I only knew about the 'light takes all paths but most strongly at the refractive index' explanation.
6:48 I should have realized this last week -- I spent several days last week going back and forth with my QM professor trying to understand how heat absorption at the level of QM before I finally understood I was at the wrong level of abstraction.
I asked this very question of my science teacher when I was about 13. I was never convinced by the answer about scatter because I knew that there was more to the "look" of a mirror. Now my questoin is finally solved, thank you.
Professor Lucid, just push your videos out to 10 minutes. You’re so close, plus we want you to get that revenue! You are great. So that would be a bad idea. Nevermind!
The only way that would get me more revenue is if I added a mid-roll ad, which I refuse to do. I wouldn't feel comfortable doing that until I hit _at least_ 20 minutes... and, even then, I'd have to have a good place for it so it doesn't ruin the flow of the video.
You should also mention the complex index of refraction, where the real part deals with dispersion and the imaginary part deals with absorbance. Additionally, the relationship with the materials complex permittivity brings an ahh ha moment to those who work in the microwave domain and allows looking at different engineering fields in a new "light". Keep up the good work.
Great video ! i was checking the internet for 3 days trying to find this gem ! Thank you ! However, I struggle to explain the fact that on glass or on water, some angles seem to be more reflective ?
I have been looking for this information for WEEKS, thank you sooo much for this man, it really helps me because I'm doing an experiment which involves light interactions. For this and your silly humour, you got a new subscriber
Glad I could help! I get a lot of comments on this video from 3D artists who are trying to understand subsurface scattering. Good luck with your experiment!
In the past few months, this channel has blown away most of the things I thought I knew about how light works. And quantum mechanics. And relativity. Most valuable patreon investment I've ever made.
Good for you 😁👍
Same.
Thanks to people like you
Apt to say, you got your priorities right
Casual flex 😂
your videos ask questions that i never knew i wanted, but soon as i see them i get sudden urge to watch the whole video!
Yes, that's one of the unique Nick's specialties :)
@@blueckaym Called dementation :D (not unique, rather rare)
@@Fish-ub3wn , haha :) ok, I plead guilty of exaggerating a little bit ... but just a little ;)
Really? I asked my teachers these things so much they would get angry. This question i asked her and was not satisfied at all. This helped me but after 7 yrs🤣🤣🤣
@@GAURAV_RANA_ that's very true, I can relate to that.
Since the academic year’s done, I didn’t want my grandsons to stop learning. They complained about watching science videos, until they watched yours. They love your content and how it’s presented (seriously, who doesn’t love graphic representations, clones and squirrels?). For four, seven and nine year-olds to enjoy science is a feat unto itself.
Your videos are entertaining and definitely informative. Please continue making videos! Thank you.
"They're going to be the same, aren't they..."
The resignation in that statement is palpable. I feel it so much.
I love this channel.
Could u explain what it meant I didn't get that sentence that much.
It's cool how lots of stuff ends being the same thing if you look deep enough -- it means there're all things unexpected relationships just waiting to be found! That's a large part of what makes me love math and physics so much.
@@Lucky10279 Dont forget biology, every animal is actually a fish!
@@Aurelyn 🤣
These are the answers we deserve but not the ones we thought we needed right now.
Nicely put :)
these aren’t the questions you’re looking for...
ob1
I'm really glad that Nick does all of the Mathematical Doodleedoo's so we don't have to.
I’ve often speculated about reflection. This video diffused any incorrect assumptions I had.
duggydo Ha! Good one!
Thanks for shining light on this subject
I saw what you did there. Nice 👌
"The mirror-like reflection in this is from the surface atoms. The color is from the layers underneath."
This exhibits an interesting difference between colored metal and polished materials. Plastic, ceramic, and all kinds of other materials will have a diffuse reflection that we identify as the "color" of the material. But the mirror-like reflection is usually neutral. Shine a blue laser on a yellow ceramic plate, and you'll get a good specular reflection of the blue light but poor diffuse reflection. Repeat the same experiment with polished gold, and both the specular and diffuse reflection will be poor. The divergence between specular and diffuse behavior drives our perception of "metallic" vs. "shiny". And the material doesn't have to have a mirror-like finish to exhibit this difference. Some "brushed" gold will still have a very color-biased specular reflection compared to "brushed" yellow plastic.
This comes up in 3D modeling, where you can typically set a material's diffuse and specular "colors" separately. For non-metallic items, the specular color is usually set to a neutral shade of gray. For metallic items, the specular color is the same as the color we associate that material with. Though sometimes the color is modified slightly to mimic the way our eyes and real cameras would process it.
Of course, when I'm modeling something, they're just values I set without wondering how they work in the real world. As always, this video was very.... illuminating.
I'd understood that the metal with a single outer electron gives a specular reflection with formation of a virtual image. White porcelain with multiple electrons in it's crystalline surface reflects white with no virtual image, even though it's surface is more smooth. This video makes the point very clear. The blue laser seems too bright and too narrow a frequency range.
@@solapowsj25 polished porcelain will reflect a virtual image, but only by a minority of the light. The rest of the light penetrates deeper, where it is absorbed (if dark porcelain) or diffuse-reflected (if brighter). You can see your reflection in a well-polished piece of dark stoneware.
It's also why in PBR (physically based rendering), there are so many property maps for example for specularity and metalness. This video made me realise how that connected in the real world. I think the whole idea of PBR is amazing as it makes it possible to measure a surface property and then simulate it, creating a realistic result.
@@nimmen Another cool rendering feature I only recently learned about is taking a 360 degree HDR image in a real environment, and then use that image to set all of the lighting for a scene. There's even a polished metal sphere that filmmakers use to grab a quick environment map that will be used to light a 3D model in its place. This way, the light map can be updated with dynamic scene elements, and the ball is sometimes moved around while shooting as well.
@@solapowsj25 The thing about metals with a “single outer electron” is that it is a loosely bound electron that all atoms basically share. This is called the conduction band as it requires very little electrical potential to move electrons from one atom to the next. This creates more like a “sea” of free floating electrons. This “sea” has a very high degree of freedom in the plane parallel to the metal’s surface which means any light that is absorbed will move the sea parallel to the surface of the metal far easier than moving it toward or away from the atom. This is most likely why reflected light is polarized parallel to the surface of the material.
I would also imagine that this high degree of freedom is also what allows the conduction band electrons to absorb most of the incident light as opposed to insulators absorbing a small portion.
Damn, your channel is Gold :D
Thank you for these great explanations.
I'd say silver, in this case. Higher plasma frequency :-)
Need to reflect on that comment
I always wondered about it but now came to know conductivity and reflection are so much connected, You Surprise me every time thank you for your efforts.
I got a similar surprise while studying electromagnetism... the relative permeability and relative permittivity of a material have a direct relation with the refractive index of the material.
Yes, conduction requires there be only one electron in the outer orbital. The stable state of two electrons alternates with one electron during electron-wave passage in current flow. These materials do not allow light to penetrate deep as crystals, plastics and ceramics do. They reflect at the surface with least distortion.
I love that you are very connected with the audience!!
Good video. 2 things though from someone "in the industry." 1), with the actual cost of material (incremental cost) because so little is used, Al and Ag are fairly irrelevant.The primary reason Al is often used instead is because of long term durability. Indeed the price to protect the Ag is more expensive (development and advertising and such) than the actual Ag! And 2, I think that green color at deep reflection may be coming from the typical soda lime glass used in second surface mirrors.
Nick coming through with videos on optics as I’m studying for my waves and optics final is a true blessing
Everyone dabbling in 3d modelling and texturing (ie blender) should watch your channel for stuff like this! Thanks much
that is amazing, and we walk around not knowing any of this... even though it''s comprehesive. love it! ☮
That was exactly what i thougth would happen, but you took it to the next level with all the details.
Thats what makes this channel so special
Wow, this was much more complex than I thought, but still you managed to explain it really well! I remember learning in school about mirrors being smooth while normal materials are rugged, but that wasn't the only part in the equation!
3:42 Light also goes through the front side and bounces off from the silver with the 2 layers of protective paint on the backside of the mirror.
Nick, your videos often make me feel that there's even more stuff I don't know. They often answer questions I didn't even know I had. Nice work!
First video of yours that I have seen. Instant subscribe. Great content and one of the only youtubers who does not beat around the bush!
That was like my whole subtopic of mirror optics in 10 mins for my HS level.
You even added some great explanation from graduation level as well
Totally loved it.
Thanks a lot it really helps my studies and feeds my curiosity.
I just can't thank you enough.
Glad you liked it 😊
I never imagined I'd see a dirty joke in such a science oriented channel lol good one
What
^
heh heh he said penetration heh heh, SHUT UP BEAVUS!
Whatever, I don’t think he said a joke.
But I liked your joke so much. It was not dirty.😅
@@imdawolfman2698 Nah
This is, like, everything i ever wanted when it comes to light-matter interactions. Five thumbs up.
Can you explain physically what is happening with the penetration depth? Why does electrical conductivity of the material determine penetration depth? Does that have something to do with the band energies in conductors vs insulators causing differing resonant absorption patterns? Also why does having a low penetration depth imply more of the light is reflected?
Yay, I've been hoping for this episode for awhile now, especially after the previous one. And it was most excellently done, thank you!
Love your channel! About 15 seconds in, I was thinking "Feynman diagrams would be a cool way to give an intuitive explanation". Get your bongos out! :) haha! Also, your point about green light aligned with something I was telling my eldest about why chloroplasts reflect green light (why are plants green?) because it is the most inefficient wavelength for absorbing energy for photosynthesis...it's no coincidence that plants and recursive mirrors reflect green!
In computer graphics we use probability distributions to model how light interacts with different surfaces. We call them BRDFs. My white material always looked a little too glossy, like satin or something... because it doesn't account for the depth and extinction parameters you were talking about! Thanks for the deeper understanding
Underrated channel.....don't be demotivated your golden day would surely come
You answer common curiosity. Bless you!
3:54
Oh balls, you stole the 'giggity' right out from under me.
Well done, sir. Well done indeed.
The summary should have this point as well:
4. It has to reflect back all visible frequencies of light almost equally to not be a distinct colour.
For the reflection to match the color of the object, yes, you are correct.... but I wouldn't have any problem calling a smooth polished plate of gold "a mirror."
I love this explanation!
I would have liked to see you explaining the result of electric conductivity in regards to the fresnel effect in metals an dielectrics, but this would have been too much.
Love it! Even though this is two years old, I wanted to praise you for your videos!
As a PhD student in quantum physics, I can only say that this is a seriously good video.
I really love this channel. I know of no other place where I can have so much fun and still learn a lot :)
Probably the best channel on physics on youtube. I don't know why I found this only a few days earlier.
This is easily one of my favorite uploaders on RUclips. You have a way of explaining these topics so clearly
My question is in the video! I'm a question clone now! 😁
I had a vague understanding of this ahead of the video, now replaced with the "nice, thank you very much" I so often have after watching. The way you make this approachable casts some light on other things (like the ocean's total internal reflection angle) and fosters further study -- and that's pretty awesome. I hope your subscriber count keeps going in the right direction :)
Hi, you are very kind to us all e you are the best teacher I know, I am a physics teacher and I didn't learn this things at the university.
Amazing work. Perfect.
It's a pleasure to help you on Patreon.
Feel comfortable to take a rest when you need.
We're here for you!
Thanks for the support!
"So why aren't all insulators transparent?" By the end, it made sense why a good mirror needs to have a specular surface (that's the one most people discuss), why it needs to be a decent conductor (shallow penetration depth that results in greater reflected light than transmitted light), and not have electron energy levels that match the frequency of incoming light (resonate absorption traps light as heat, whereas dissipative absorption allows it to be released as EM wave patterns that can build up at the angle of reflection)....but I feel like that one question thrown in there wasn't answered. Am I missing something? What causes insulators to be opaque? is that simply a result of the random way the atoms are organized inside that produces constant absorption and emission internally? Does this mean opaque insulators capture more heat as a result if the continued oscillations of these atoms and increased kinetic energy from those oscillations? If not, why doesn't this transmitted light come out the other side of opaque insulators? (Sorry I know this is a long comment but I love your channel and your videos are so enlightening - just trying to wrap my mind around that piece)
I love physics i am in 10th grade i will surly will become a theoretical physicist i am glade i understood nearly 75% of the video so love you sir😊😊
Dont make your mind up too soon. Give all of physics a try and see where it goes. Thoretical stuff is really dry, though sometimes really exciting and mind blowing. Nowadays theoretical physics is really advanced and the experimentalists cant really keep up with all the stuff proposed. So the theorists dont get enougth imput back, as it seems to me at least. Anyways... Keep your mind open and question everything. :) I ll study physics soon as well and will by great chance be an experimentalist. Have a nice day!
And don't be surly. :)
I hope you love math as well then.
Goodluck with ENC 1101 😄
(Was looking for the color of gold because of SR questions. Don't see them. But .. it's unbelievable how many comments you answer.👍 I don't think any other youtuber does that.)
It's important to me 😊
@@ScienceAsylum Didn't get a notification again .. someone is hacking me 👀.. 👁 you! .. 😉.
Jk, but I wanted to ask you. (Hopefully I don't ask too much.) You sometimes refer to brilliant.com. I am wondering .. can you learn physics there at "master degree level"?
Brilliant teaches a lot of things to their users and it's great practice. Some of it could be considered masters level material, but most of it is bachelors level. *To be clear though:* No online service could _ever_ replace an actual degree.
Nobody:
Nick: *P E N E T R A T I O N*
The surface of paper is not only rough, it's more like a fuzzy blanket or an air filter. The filaments of paper go every which direction, but are smashed down so overall it's a "flat" sheet.
3:51 "Its something we call Penetration Depth" Was that innuendo clone?
Hey Science Asylum, another great video as always!
As you know, we use the index of refraction in fiber optics, basically the backbone of all telecommunications.
However, in my industry the “last mile” is usually coaxial cable, RF over coax. For the longest time, since the 1960’s, the manufacturer of the coax has specified the Velocity of Propagation of the cable, which is the percentage of the speed of light that the signal can travel through the cable. Well, nowadays this is actually very important for everything to work correctly (TDMA for example).
So here is my question:
The VoP is just a number from the manufacturer via quality control testing. Our servers work with each individual customer modem to negotiate the proper timing required to use ATDMA for that specific distance of coax, never actually solving for the VoP. We can use the VoP to detect echos of signal and get a pretty good idea of where a flaw or crack in the cable is located (within 40 feet) and repair these before corrosion sets in and the signal gets seriously impaired.
Yet, as I understand it, there is no physics method to precisely derive the actual Velocity of Propagation of a RF signal through a medium.
Are you willing to do a video on Velocity of Propagation of RF through a dielectric? Pleeeeeeeeeeeease.
There are a lot of things in physics/engineering that are much easier to experimentally measure than theoretically predict. The refractive index (mentioned in this video) is a good example. While we _could_ derive it theoretically if we could get a computer to model the behavior of light properly in the material, I don't think anyone ever _has_ done it. It's just not worth the trouble.
1 question here:
"Mirror mirror on the wall, who's the best physics RUclipsr of them all?"
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-It's Nick, it must be Nick!
0:08 I love how one of the questions is, "If white color reflects all the light, what a mirror does?"
its like The Science Asylum reads my mind. Thank you Nick
See if I understand correctly: a red object, for example, is red, because its electrons absorbed the other colors by resonant absorption, while the electrons (or the atom as a whole) absorbed the red light by dissipative absorption. Thanks, your videos are great!
Me before the video: "Ugh, this is gonna be really basic. I already know this one."
Me a few minutes into the video: "nvm"
I still haven't recovered from your previous video about how mirrors work, but thank you for this second jab to the brain :D
You're welcome 😉
I’m gonna have to be that guy and ask: “WHY does higher conductivity mean a lower penetration deapth”
And great video as always, made me ask myself a ton of questions, which is always a good thing🙂
Higher conductivity generally means more free flow of electrons in the material, which interferes with the lights ability to penetrate
-A guess
I love how you sum everything up at the end of each video. It's really helpful. ;)
Polishing to a mirror shine is a term for a reason!
2:15 I always get pumped when this music starts playing!
You're so brainy, but at the same time totally looney, I love ya!
Love the video! I was all smug face when I clicked on it knowing "paper is not smooth so it's not a mirror". Glad I watched it :D
Glad I could surprise you a little 🤓
This actually makes 3D modeling more understandable.
3:52
Seriously I didn't see that coming
How do you always manage to get things right. Seriously, a lot of professors are stumped by a fair amount of questions you answer.
I do a lot of research and keep learning. Unfortunately, many professors stop learning after they get their degrees. (As someone with a chronic illness, I can tell you this is true of many doctors too.)
I was looking for a comprehensive explanation of why light is "bending" when crossing between 2 different mediums for years. This helped me a lot. Thank you.
Whoa.... I didn't think being a mirror would have so many properties of its own. This video was phenomenal!!! Understood each and everything clearly...! Thank you Nick!
I'll never look in the mirror the same way I used to again.
@eatskittensfordinner now I am in a mood for watching Airplane!
I believe cellulose polymer in paper is actually spectacularly transparent, not quite as transparent as glass but in the grand scheme of things not too far off either. The diffuse reflection occurs purely due to the shape that the nature delivers it in, hollow squiggly ragged tubes with a lot of semi-regular partitions, so a lot of boundaries at which the light can exit or get reflected.
People have used this property to make "transparent wood" and wet t-shirt contests.
I caught myself trying to like this video like 5 times after I'd already pressed "like."
You should cover fluorescence and photon tunneling in some butterflies' wings... they amplify colours by converting wavelegths to the visible part of tge spectrum, and redirecting photons which would otherwise be absorbed by ir lass through the wing.
He's got me saying "super zoom" before he says it :)
Honestly, I wondered about that, too. Especially after your last mirror video.
Thank you for the great explanation!
Your vids make me think "should have taken physics in university"
Dude, you get better with every video. Great channel!
Me before watching the video: I know why white materials aren't mirrors, it's because of the imperfections on the surface!
Also me 1 second later: .....that's not the whole story, is it?
I have a lot of questions:
1. Why do we need to have low penetration depth. If something reflects 95% light specularly and the rest of the light just goes in somewhere, I have a pretty good mirror. Don't I?
2. How does low penetration depth translate to metallic luster.
3. Why conductivity is related to penetration depth in the first place?
4. If only resonant absorption can actually contribute to the internal energy of the material and dissipative absorption cannot. When the intensity of light drops of exponentially where does that energy go?
5. Related to 4. If different things reflect and transmit different wavelengths differently and that light gets absorbed. Why doesn't it heat up the material?.
6. If I have a lot of infra red photon and if it cannot be absorbed through resonant absorption, will they never be able to heat up the material? Or infra red photons are bound to be absorbed due to alot bands really close to each other at higher levels or the vibrational or rotational bands play a role. I have read about them but don't understand it.
7. How does the energy absorbed by resonant absorption gets transmitted to other atoms. Isn't it bound to the kinetic energy and potential energy of electron?
8. If I have 156.5 cubic meter of glass. It won't be tranparent, right? Or do I need to mutliply that to five too. Like a km or something. Does it mean that if I am within reasonable penetration depth. Everything would be transparent?
I have had these questions for a long time. My teachers couldn't answer them. Now, I have more. Please, Nick, let me understand all of this once and for all. Possibly with a dedicated video 🙏
1. If your penetration depth isn't small, then it _wont_ reflect 95% of the light.
2. Low penetration depth mean less scattering.
3. Light is an electromagnetic wave, so it's interaction with a material is governed by how that material interacts with the field.
4. I didn't mean to imply that dissipative absorption couldn't contribute to the internal energy of the material. It can. Just not _nearly as much_ as resonant absorption. In science, there are very few clear lines we can draw. Most things are on a spectrum and absorption is no exception.
5. Material can only be heated by light they absorb and don't let go of. If the light is reflected or completely transmitted out the other side, then the material didn't keep the energy.
6. See my answer to 4.
7. No, the electron loses it and falls back to the lower energy state. It's just that the energy didn't get emitted as a visible photon. It became heat instead.
8. That would obey the same percentage rules as the mirror, so you'd need it to be about 780 meters thick before the intensity would get down to 1%. Yes, if you make _anything_ thin enough, it will be transparent... even a sheet of metal. That's exactly how Rutherford did his gold foil experiment. He made the gold sheet so thin that it became transparent.
Thank you so much Nick, some of them were obivous, but clarify this too:
7. When the electron falls, does it do smaller successive jumps and produces infra-red photons. Because shouldn't the photon that was absorbed should come out too. What I wanna know is how is it converted to heat?
5. The point was if all materials who are not white keep some light in. Why don't they just heat up?
7. No light is emitted from the quantum drop. The infrared light you're talking about is emitted because of atomic collisions, not for any quantum reasons.
5. If an object is a color other than white, then it _will_ heat up. Even white things aren't perfectly white, so they heat up too. Eventually, they'll reach an equilibrium with their surroundings though where they're emitting heat as much as they absorb it. At that point, they'll stop getting any hotter.
I am taking too much of your time,
How does that visible light convert to heat then.
I have a question.
Does dissipative absorption result in the frequency of light (colour to us) of an object given off or the reflected light of a mirror?
p.s this channel has really inspired me a lot so thank you.
Yes, dissipative absorption is the kind that result in the color we see on objects. The colors (frequencies) near the resonance stay absorbed and the rest are re-transmitted dissipatively.
This only recommended to me 4 yrs later, and i am so mad, i've subscribed for more than 2 years now
You should've had at least a million subs by now
Thanks for valuing my work so much. I kind of have a niche style though. My guess is that I'm already at the sub level that style allows for. It's fine though. I'm comfortable with it.
Meerer is what we like...
This guy makes video about questions I never knew I wanted the answer to.
Wow, this answered questions I didn't even know I had, hidden deep in my subconscious. Electrical conductivity, makes so much sense now!
Always enjoy when the music changes into "We're getting Serious" mode 😂... this time at 2:15
Fantastic video! This is the best summary of reflection, refraction and transmission explained all together that I've ever seen. Normally these are presented as separate things but they're really all part of the same process. How does the photoelectric effect arise from these?
The photoelectric effect arises when the photon energy (usually at least UV) matches the gap between the valence and conduction bands in the solid. Electrons in the valence band of a solid (usually a semi-conductor) can jump up to the conduction band (or sometimes even free themselves from the solid all together).
The Science Asylum So it's like light reflecting not into our eyes but into electricity. 😊
"Conservation of energy shall not be violated!" Lol. The way you say that always cracks me up!
Don't forget about Noether's theorem. That video was so interesting. I remember my physics book specifically said that scientists had _never_ found any violation of the conservation of energy, which prompted me to immediately write in the margin that that's actually not true because of Noether's theorem, remembering your video. Anyway, not criticizing this video in any way. For all practical purposes, I know energy of a closed system is conserved, so it makes sense to treat it that way. I just like seeing all the connections between your many different videos and math and physics concepts in general. Finding those connections makes everything more interesting.
Right, it takes a lot more extreme circumstances than some light interacting with matter to violate the conservation of energy. As for your textbook, it's standard procedure to lie a little bit to intro students. I'm not saying I agree with it, but I'm not surprised your textbook does it.
Hey Nick, great video as always.
But is there a chance you could do a video related to nuclear physics? Why is the nucleus so special?
What is alpha and beta decay?
A subject I know and love (spent alot of years coding ray tracers) and you still covered more than I ever thought of. You rock :)
Oooooooooooooh, wow! Thank you! The refractive index of light going through different mediums has baffled me for decades! Up to now I only knew about the 'light takes all paths but most strongly at the refractive index' explanation.
6:48 I should have realized this last week -- I spent several days last week going back and forth with my QM professor trying to understand how heat absorption at the level of QM before I finally understood I was at the wrong level of abstraction.
Another good one Nick! Keep em coming.
Nick! You must do a full video of Florescence and Phosphorescence.
lol...The Penetration Depth eyebrow raises... You have won my subscribe sir...
I asked this very question of my science teacher when I was about 13. I was never convinced by the answer about scatter because I knew that there was more to the "look" of a mirror. Now my questoin is finally solved, thank you.
Glad I could help 🤓
Nick: You don't need quantum mechanics for this.
Also Nick: shows light as a wave and talks about quantum energy levels.
;)
😂
Professor Lucid, just push your videos out to 10 minutes. You’re so close, plus we want you to get that revenue! You are great. So that would be a bad idea. Nevermind!
The only way that would get me more revenue is if I added a mid-roll ad, which I refuse to do. I wouldn't feel comfortable doing that until I hit _at least_ 20 minutes... and, even then, I'd have to have a good place for it so it doesn't ruin the flow of the video.
The Science Asylum Ah I see, excuse my naive understanding of ad revenue! However good point, I appreciate the thought put into these videos.
@@ScienceAsylum Man, You are Awesome. And You too, the other one...
You should also mention the complex index of refraction, where the real part deals with dispersion and the imaginary part deals with absorbance. Additionally, the relationship with the materials complex permittivity brings an ahh ha moment to those who work in the microwave domain and allows looking at different engineering fields in a new "light". Keep up the good work.
I didn't want to scare anyone with imaginary numbers this time through.
Can you please, make a video on "resonant absorption and dissipative absorption..."
I must say there is so much in the „normal“ things surrounding us! That’s really mindblow!
Great video ! i was checking the internet for 3 days trying to find this gem ! Thank you !
However, I struggle to explain the fact that on glass or on water, some angles seem to be more reflective ?
Glad I could deliver 🤓 (Also, look up Brewster's angle 👍)
I have been looking for this information for WEEKS, thank you sooo much for this man, it really helps me because I'm doing an experiment which involves light interactions. For this and your silly humour, you got a new subscriber
Glad I could help! I get a lot of comments on this video from 3D artists who are trying to understand subsurface scattering. Good luck with your experiment!
It's amazing but thanku sir for such a simple explanation👌🙏
I am learning 3D CG and your video make me understand more about those BSDF PBR shaders I have been using. Thank you!
You're welcome! 😊 I have lots of people in the comments saying this and I'm always happy to hear when my videos help.
This dovetailed nicely with my Optics class this semester....
One of the best videos on the topic, answered so many questions I had in past...