De Broglie wavelength | Physics | Khan Academy
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- เผยแพร่เมื่อ 27 ก.ย. 2024
- In this video, David explains how Louis De Broglie got his Nobel Prize for the idea of matter having a wavelength.
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"Luey deBroy"
Gotchya!
they're bots, dont fall for those.i
This is absolutely amazing. Physics has always interested me but is not my best subject. I came here because my Modern Physics professor suggested this video. I see why he did so--this video does not only make this concept extremely easy to understand, it made it interesting. I wish all my professors could make difficult topics such as Modern Physics and Quantum Mechanics so enjoyable. Thank you!
That's the explanation I wanted to know!
Thanks a ton for not only spreading knowledge but spreading it in explicit manner.
PS - This is the top channel for us(students) to learn :))
You won't even realise how many more major concepts of physics he has explained just in 10min of video that would actually take you 10years to comprehend =D
Simply aesthetic 🌺🌺
this is one the best videos that explains this concept so beautifully WOW
Excellent job framing an important idea that's hard to get a foothold on! How about making another one on the Davisson-Germer experiment itself?
It's been three years and i'm still pronoucing the guy's name Broglie.
Me too, and I made this video :)
@@WeAreShowboat Really?
@@hadmeinthefirsthalfngl2717 💯
Ya
but it always is pronounced Broglie.
depending on how you pronounce the name "Broglie".
Just an awesome video. I read the textbooks, I understand the books, but I just didn't get the big deal until this explanation. Thank you!
❣️
Right
This video highlights the important point about the quantum nature of light and wave particle duality. There is a somewhat different way of explaining the physical nature of light and the photoelectric effect by following the Spacetime Wave theory.
In the Spacetime Wave theory, light is described as a real physical wave disturbance of spacetime moving through space. This is like a gravitational wave but at a higher frequency. In the Spacetime Wave theory light exists in discrete quanta of energy because of the way that light is emitted by a change in energy level of an atomic electron. Light waves are not inherently quantised but are quantised due to the way they are emitted.
So we abandon the concept of wave / particle duality and instead consider the photon to always be a wave quantum. In the experiment to demonstrate the photoelectric effect the wave quantum is the perfect description because the wave part describes the energy (E=hf) in each quantum.
The Spacetime Wave theory goes further by describing electrons, protons and neutrons as looped wave disturbances of spacetime in spacetime travelling at speed c in the loop. This provides a similar model to the de Broglie model where there must be an integer number of wavelengths in the loop and this provides the correct results for the emission of a wave quantum (photon) when an electron changes energy level.
The advantage of the Spacetime Wave theory is that it provides a deeper understanding of the real physical processes taking place when looped waves in spacetime change state.
For more detail see:
www.academia.edu/5927513/The_Spacetime_Wave_Theory
www.academia.edu/5038836/The_Unification_of_Physics
Richard
Thank you very much . The weird thing is I was so happy watching the video ! I lived the video second by second .. I think I should specialize in Quantum Physics .
No one initially performed an experiment to test De Broglie's hypothesis. Instead there was an experiment that had unexpected results. De Broglie's paper was used as the explanation for those unexpected results.
okay so this is basically the first video which made me understand the De Broglie Wavelength. I didn't even know that it was about electrons working as waves
When is your birthday David?
We are celebrating teacher's day 2.0 on the day your birthday falls.
Period.
That's great what debroglie found , he didn't get the formula for matter using mathematics, he just predicted that might be true as it is valid for light
2:43 heres come my boy...
None other than... LUI DE BROY
2:15. Because of you now I have to cramm some questions and answers!!
Nice explanation, BTW We can also derive this expression from equating energy from
1. E=hf(Wave nature)
2. E=mc^2(Particle Nature)
but how
@@darkzonegaming9169 write C as Velocity, f -> c/Lambda
@@shivensaini3643 thanks mate
Really found your channel with the best explanation…hope you upload more related videos
Wow, you explained it so well, I think its the best explanation video regarding this topic on TH-cam.
man! i'm in love with you ! thankyou so much
My apologies in advance if you enjoy spookiness.
Dipoles interfere, massless or not.
A dipole does not interfere with itself. Dipoles tend to be overlooked when they pair up 180 degrees out of phase with each other, with consequent signal drop out.
Photons are extended polarized electromagnetic dipoles. Polarizers are re-polarizers. Opposing helicities of polarization can be induced by a linear polarizer.
Electrons are magnetic dipoles due to their spin. Their spin is both quantized and tied to their speed. As matter dipoles they like to pair up 180 degrees out of phase.
Ions are electric dipoles and spinning ions are magnetic dipoles, their spinning involves contact with surroundings and can be synchronized.
This channel is a huge disservice to physics and the next generation
Thanks . I was able to learn clearly with this video .
Tomorrow is my final exams and now i am confident , thanks to your channel.
Great video thanks
Really great
U make the idea very easy to understand
I can't know how much I can thank you
Khan Academy is also nice for math practice as many know.
Damn. He teaches soo well, not even tryin to sound like a cringe comment, but each of his lectures is so good.
Amazing video you made. I was not understanding this case but your video made it more easy for me to understand. Thank you
In back of the center light focus is the unknown
Anyone know this software which is in this video for writing please i wanna know please
it's been 10 months, but it's called smoothdraw
@@MsQuikly , thank you very much. ☺️
That dislike is so unfair. I think this lecture is very interesting for a beginner on quantum mechanics.
Beautiful lesson. Thank you!!!!!!
Best class ever.....doesn’t even sound like a class!!!!!
best physics teacher ever...down with this expensive and inefficient u.s. university system..
Quantization always arises from boundary conditions. It's not a "particle nature" of light quantizing the photoelectric effect, rather the boundary conditions upon the electron that prevent it from accepting low energy waves. Light is always a wave and may always be calculated as a wave. Particle models are always simplifications of the more accurate wave calculation. "Wave" is always correct, "particle" might sometimes be correct.
But... We hypothesized the photoelectric because treating light as a wave doesn't work; it leads to the ultraviolet catastrophe, even without electrons getting involved.
Hahaha thought it was "lu-wis de brog-lee"
This explanation was amazing. Thanks
Thank you so much for such a elaborated and good explanation
Awesome class sir
Understood every part of it !!
Thank you sir
9 dislikes,,,, i mean why would people give it,, this video cleared every doubt in my mind,,, what more do these people want,,, why would they dislike it without any reason, they are cruel af!
Double slits cause interference of light waves whereas diffraction pattern results from a single slit.
The light diffracts at both slits thats what causes the interference.
The explanation is just amazing
so does that means that everything in this universe can act as a wave as well as a particle depending on the experiment we are subjecting the object to?
I guess. My physics teacher told me even the particles in our bodies spread a very miniscule amount when we go through doorways... Donno if its true though, it's really weird and hard to believe
yes, everything has a wavelength
That was fascinating.
Thank you.
fabulous video...it's like crystal clear
But this equation is derived for massless particle
How can we use mass of electron
I think it's because the mass of an electron is ~0 kg, but there is still a mass.
Incredible explanation
So the particle nature of light was shown by light knocking away electrons in metals, but then electrons were shown to also be waves. It seems to follow naturally that one would then try to explain the photoelectric effect by considering both light and electrons as a wave. I'm sure someone tried this, but does anyone know what was the conclusion? Does the photoelectric effect not work considering both light and electrons as waves? Why?
Awesome video !!! Thank you!
Excellent! Thank you. ❤️❤️
It is very useful. Thank you!
What if what we’ve always called particles are always just waves with super small wavelengths?
Awesome video thank you sooo much
I love this channel and their website as well.... Plz make a video on Davison and Germer Experiment.... I have my finals with in five days ..... Please help me I love PHYSICS and wanna get my application accepted in an engineering university....
They understand
THANK YOU!
fax
brillant👍
Thank you.
Thank you! Really, Thank you!!
Is the equation only true when the particle is travelling very closer to 'c'?
Or, at any velocity?
Hasnain Iqbal, i'm probably too late, but i'll try to answer. This equation is valid for "any" value of speed. You can see in books some exercises of calculation of a baseball wavelength, for example.
As a french speaker I think we spell it " De Brogg_ly "
C'est une exception.
Les Ducs de Broglie sont d'origine italienne et c'est en françisant leur nom quand ils ont émigré vers la France que c'est devenue Broglie.
La prononciation d'origine a cependant été gardée.
I dont think a single person in india say 'De BroY'
You do!
Right
It's mentioned in Ncert physics class 12 part 2
I do coz i have learned French in my elementary school😁😁
in ncert class XII in dual nature chapter it actually mentioned in brackets the pronunciation,but no one pronounces it that way
Dude. The Broglie effect is just... The mirror effect... That's it. Only were harnessing a mirror image of the object in the form of energy.
That's why the Broglie effect occurs mostly on metallic surfaces,
6.626.4 h constant(photons)
really helpful
people keep saying this is a good video but it didn’t explain anything to do with the Khan Academy test on de Broglie Wavelength at all
Thanks bro
Good explanation bro!!
Wait....I have a question how we can relate to quantum mechanics it was so confusing thing
Because the statement proposed by de broglie is before Eisenstein right!!
de Broglie made his statement in 1924, 19 years after Einstein published the photoelectric effect paper. At the time of Einstein's paper de Broglie would have been approx. 13 years old. :-)
awesome thanks
ok. i still don't have a good intuition for how can matter particles have wavelengths? we can conduct experiments to prove matter has wave character. but what are these waves? what are these matter waves or deBroglie waves?
Tushar Pal This wave doesn't have the physicality that we see in other waves like sound for example...
It's a wave where you can search for the particle and make sure where it really is while moving(of course as you mostly know that can't be seen on the larger scale) I think this one is so vital to get this...
"Minute Physics" channel has a good video for that try to find it
fascinating!
Probs! best video!
I just have a doubt...in double slit exp. the pattern that forms is interference pattern right...but you are saying that it forms diffraction pattern(which is formed for single slit exp)...??anyone do clear me out...!pls
The reason the double slit experiment works the same for light, electrons and baseballs is because what we are detecting aren't "particles". We are always detecting quanta of energy. Energy is always the same, no matter what kind of system has it.
That was cool 😃🔥
yo your a gangster with that mouse accuracy
Again i am saying the same thing you are awesome 😎
If matter particles have a wavelength, does this mean all condensed matter bodies, such as a human body, behave as a wavelength as well? Or is this just relevant to each individual electron particle?
Kevin Manganini everything behaves as a wave. But wavelength is very very very small for human body
But what happens if v goes to zero. With momentum (p=mv) going towards zero lambda would get very large, no?
Then you won't exist.....no matter has zero velocity.... If so your wavelength goes to infinity
@@goodn1051 then you're Everywhere!
Good question, De Broglie's wane nature of particles shows all particles you are made of are waves, proving something even basic. It proves all quantum fields are basic, particles are secondary. Similarly the whole universe is an evolution of the Schrodinger's wave function. But sadly we don't know the infinite axiom algorithm, how quantum states produce classical objects, like stars, planets BH etc. Einstein craved to improve QM, but failed, because this algorithm is known only to God. Mankind can at best arrive at a finite axiom algorithm.
You forgot to mention that the electron changed patterns only upon observation they noticed this after many tests.
excellent
awesome !
Louis ma Boi
man that was a nice explanation if only our teachers explained like this, sad .
Great presentation but light is a partical and not a wave. It’s just a probability distribution and the delayed choice quantum eraser kills the wave particle duality
I'm not a particle or a wave, but I play one on TV.
Nice
I still have the question 7:54
What is that ?
But why the mass of electron is not taken, the equation for wavelength is for light whose rest mass is 0 but rest of electron is not 0.
Sir kindly help me. I won't lecture on mie-gruneisen equation.
10:44 false the bohr/bar broken Theory
Correct #PrimerFields
Ask yourself where do discretized frequencies (quanta of light) come from in the Photoelectric effect experiment? Do the energy-quanta come from the light itself or from the electron within the atom? Great respect for Khan, but they blew it here. All quantization effects come from boundary conditions of wave equations. In this case, the energy levels (and thus the work-function) come from the spherical solution of Schrodinger's wave equation of the atom. Similar to Blackbody boundary conditions. Boundary conditions always lead to quanta and if you see quanta, they only arise from boundary conditions. (more..)
When light strikes the atom, light either has the correct energy to pop the electron or it doesn't, based solely on the electron in potential well. Different potential well, different light-energy requirement. And that requirement is based solely on the potential well (boundary condition) and the allowed states therefrom. It is the atom that dictates quanta, entirely independent of the light's energy (frequency). And the electron pops out of its potential well only when light's energy matches the atoms requirement. Otherwise, the electron stays in place. Therefore, light is not "quantized" (E=nhf), the atom is quantized.
The fact light travels as a discrete photon is an entirely separate subject. Light's energy levels are simply not quantized.
There is a closed form solution to the hydrogen atom. It's shameful that after a hundred-years, physics still teaches this topic incorrectly. And by shameful, it means every single physicist on the planet should be ashamed. Sorry to be so blunt, but I've been posting about this glaring and obvious mistake in physics orthodoxy for more than a decade.
Therefore Khan, and all of physics has been wrong for a hundred-years. Photons are always waves. So-called "particles" are never particles, but rather waves. In the entire universe, there isn't one single particle. Only waves. And THAT is deBroglie's lesson.
would you say that this is why atoms appear "mostly empty" when other particles are shot at them? In other words, the chances of "hitting the electron" are small for the same reasons as the proper amount of energy needs to be deposited? Forgive my language as I am new to this subject
@@JoeHynes284 - Ever been to a wave-pool? Most wave-pools can make a single wave, if they like. How big is such a wave? What is its extent? (let's assume it's 3' tall x the width of the pool x 10' for this discussion?). Can one have a half-cycle of the wave? (hint: no). If a wall were setup in the path of the wave, wouldn't the wave reflect? (hint: yes). If the wall were at an angle, would the wave reflect at that angle, the same angle as a billiard-ball reflects? (hint: yes).
Is the water-wave in the wave-pool a particle? (hint: no). Yet, the wave reflects at the same angle as a particle? Could we use a billiard-ball model to predict the wave's reflection angle? (hint: yes). Does the size of the billiard-ball matter in such a model (hint: no). Billiard-balls in this case are what's called a "particle model." Particle-model's (same as billiard-ball model's) ignore the size of the wave to make predictions. Accurate predictions in many cases.
One could use the wave-equation to calculate the reflection-angle, but it takes pages of equations. OR... one can simply use the particle (billiard-ball) model and solve it without a single calculation (incident angle = reflected angle). Such a simplification doesn't make the water-wave in the wave-pool into a billiard-ball, even though the billiard-ball model gives the correct answer.
Photons are waves. Electrons are waves. Neutrons are waves. There are no particles. There is no wave-particle "duality," because there are no particles. Sometimes, the billiard-ball model simplifies the solution of a problem, but that doesn't make the wave into a particle.
Extending the wave-pool analogy a little further, imagine a 20' circular pool? Now we install the wave-making engine into the pool and start it up? Imagine the waves bouncing off the walls, eventually in every direction? Soon a standing-wave pattern results? Ask yourself, where is the wave? Isn't the wave bouncing back and forth within the pool? Who can say exactly where?
Before, we could point to a cycle or two proceeding down a flat pool? And we could say, "that wave's about 10' from where it starts to where it stops being a wave?" But in the circular-pool, the wave's bouncing everywhere and we have trouble pointing at one spot to say, the wave is here or the wave is there? Physicists confuse wave-in-a-box with particles or even "particle-in-a-box." Because as we now know, there are no particles.
If one looks in the circular wave-pool, they can't say, the wave is here or the wave is there, because the wave fills the pool. It's everywhere, yet it's elusive. That is the nature of a wave.
Once you study wave-mechanics, you'll go just a tiny bit beyond the pool analogy. Because, as anyone can see a 30'-wave will not fit in our 20' pool? Only certain-size waves will fit inside the pool. The size of those waves is determined by the size of the pool. And the size of the pool is called a "Boundary-Condition."
There are several other differences that require we leave the pool-analogy behind. 1) single atoms are essentially lossless, the electron will slosh around forever (where our water-wave loses energy to friction). 2) Electron's are held by the atom's boundary-conditions until and unless the exact right amount of energy is provided to free the bound electron (unlike a water-wave).
Went through all this to expose the problem embedded in your question. First, there are no particle's to "hit" with or against the wave "in the wave-pool." There are only waves. Waves inside the wave-pool (atom's boundaries) and waves to strike with.
Hope this helps?
@@tomnoyb8301 wow! I cannot thank you enough for your time! Have a great weekend and thank you!
@@JoeHynes284 - Yw.
Anyone know where I can find his paper?
awesome
Hi! where can i read the paper of De Broglie?
If photons gave all their energy to electrons how can Compton's effect be possible?
According to this: physics.bu.edu/~duffy/PY106/PhotoelectricEffect.html, photons only transfer some of their energy to electrons. I think the narrator may have misspoken when he said that photons transfer all of their energy to electrons. I think he really meant to say that light energy is just quantized as photons.
@@Limonene788 I guess it would transfer all the energy if it is absorbed, but if it's scattered then only part of it.
can we use E=hf for an electron moving with velocity v ? If yes ,why ? If no,why too ?
Thanks for the help :))
it's 12.27 not 1.227
I think... It works until the v starts getting relativistic
I got a question. As far as we know, electrons have a mass, how can we use the same equation related to the photons (non mass particles) to particles with mass?
lambda = h/p seems not be right in that case, anybody could tell me why am I not right?
bit of a late reply. you’ve probably figured the answer out by now, but just in case:
p=mv is only used for the momentum of an object with mass. massless particles (“matter waves” such as light) have a momentum of p=h/Lambda.
hope that helps