Photoelectric Effect Demonstration
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- เผยแพร่เมื่อ 5 ต.ค. 2024
- The Photoelectric effect helps to illustrate the wave-particle duality of Light.
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What a great name for a camera assistant! Julianna Photopoulos, I hope your career in capturing light excels and brings you joy and prosperity.
Finally I understood photoelectric effect after 5 years of passing graduation, just from a 3 min video.
it sucks because schools only teach theories but never actually demonstrate it in real life
same happened with me
@@unesalotte3419 exactly.
Taxa. This uuaiuiiuuuuuuuuuzuzu7rrriRwgtyuopppooiiiijiikolpoooonb. This
😁😁😁😁😁
Wtf
Wow, this short video is pure masterpiece, very brief but concise, includes a nice demonstration and most important facts. I just learned a ton! Thanks
What did you learn in class
me: 1:19
I can relate 😂😂😂
I need a girlfriend s3x day
Absolutely nothing
🤣🤣🤣🤣🤣
thank you so much for this! i got a test tomorrow and the fact that this video gets straight to the point really helps.
You deserve a thumbs for making this a simple and unbiased explanation.
THE BEST VIDEO I SAW ON THE TOPIC!!! Really astonishing!!!!
Nice work!
+Mohamed Khaled the only astonishing thing is you think it's right,
+DarkDuke 2015 What? You think we were duped by this vid or something? What do you mean by "it"? Do you mean the vid or Einstein's work? Well, if you have something of evidence to show against any of those two, I'll be more than delighted to know it!
P.S. That wasn't a joke; I love science and would be really happy to know about any new scientific research or evidence on the topic!
I mean that the photoelectric effect does not do anything at all to prove that light is particles and not waves. All it shows is that em waves effect electrons nothing more.
+DarkDuke 2015 Nice remark! I'm happy to find someone who reasons and thinks about what we call "accepted logic." I've thought in a similar way when I first learned that at my chemistry class, but you know, to be honest, 1- Particles push particles, and it somehow seems right that packets of concentrated energy (waves) act like particles (photons) that affect (or push) electrons.
2- We don't see below the surface; most chemistry courses (and almost all scientific courses, in fact, almost all education) sadly tell you what is (or what they think is) without telling you why it's so. So there might be some mathematical or scientific base on which this is made, which, of course, we don't get 'cuz it's harder for those who teach us to explain it.
Finally, I wanna thank you for thinking and for having the guts to argue with Einstein, which proves, no person is infallible. There might be someone, later on in the future, who will disprove what we accept today as reality, just as we disproved what those before us thought to be reality, and I think this is one of the many beauties of science: we can always add to it. Oh, and speaking of adding, scientists have recently added 4 new elements to the periodic table, putting on the finishing touches after more than (well, I don't know when was the original periodic table made!) years!!!!
Thanks again, for thinking!
+DarkDuke 2015 Sorry for being a bit long, but I love reading and writing!
Wow, this was really simple and it has helped me quite a lot. Thanks!
Very nice experiment! Great to do with students! One note about the presentation. The photo-effect CAN BE DISCRIBED with the WAVE theory of LIGHT if we take into account the quantum structure of the electron inside an atom (it was actually done soon after the atomic model was discovered). Here it is very interesting to notice that the very same photoelectric effect can be described by two models at the same time: quantumlight+clasical atom and classical light+quantum atom. Isn't it wonderful?! Well, now comes the question for you: "Which model to choose?"
Oxana Mishina // Photoelectric effect, at the time, was impossible to explain by wave model of light. This effect was the beginning of new physics with Compton effect, etc.
Thank you Chetan Bhagat for teaching this concept in much easier way than my teacher
Thanks for a simple and coherent explanation for a complicated subject
انا من العراق شكرا لكم لنشر العلم طالبة مرحلة الأخيرة من الثانوية
Does anyone confuse about the induction part? I suppose the glass rod hold in the hand is negatively charged after rubbing with the cloth (not positively charged mentioned in the video), so the metal plate can be positively charged after induction. Then the electrons will flow to the metal plate when it is earthed. The whole process can end up with exceed of electrons remaining on the metal plate and leaf.
I was also confused when I watched this, and then did some reading i came up with the same conclusion as yours
There was no lie in the video; the rod is positively charged. Bringing the rod close to the zinc plate creates a positive voltage in the plate without charging it. This is why the leaf rises at 0:59. Now that the top of the plate has a positive voltage, electrons move onto it from his finger when he touches it. When he removes his finger again, the electrons are trapped on the plate.
Are you sure that you aren't making the acrylic rod negatively charged?
This is something that earned Einstein the Nobel Prize
He touched the zn plate to do earthing and remove positive charges. Feels gud to understand science!
Wow, beautiful demonstration 😊, simply awesome💗.
I liked the way how easily entire set up is made with simple things.
My opinion:
I think Negatively charged Zinc is required so that once electron gets removed from it ,then don't come back(excess charge has tendency to go away from each other)
BUT If we started with neutral metal, then photo-electrons would have come back again to metal due to attraction of nucleus.
OVERALL enjoyed the demonstration ☺️👍👍
👍👍
At first I was expecting when he brought UV Lamp closer, then we will be "seeing" UV Light getting fall on zinc, ....but soon I realised it is UV ( "invisible light")... How easily one get carried away under the common expectations 😅😋
That was very interesting thank you for the time spent to explain this phenomenon!
Brilliant demonstration, thank you!
Brilliant: essential, clear, no sci-fi; pure science!
A good teacher you are
In the photoelectric effect experiment ¹ ²:
- A metal plate, usually made of zinc, is connected to an electroscope.
- The electroscope is an instrument that can read the presence and relative amount of charges.
- The metal plate is negatively charged by bringing a negatively charged rod close to the plate without touching it.
- The negatively charged rod attracts some positive charges from the hand onto the zinc metal, and the positive charges remain on the zinc metal after its contact with the hand is removed.
- The needle of the electroscope should deflect to indicate that the metal plate and all the parts in the electroscope connected to it are charged.
- When a UV light is shone on the plate, the deflection of the needle decreases or disappears, indicating that the metal plate has been discharged, i.e., it has lost its negative charges.
Muito bom , me lembrou minhas aulas na faculdade de Física, todo experimento é válido e de alguma forma os de Física são muito belos e harmoniosos parabéns
This is beyond explicit! Thank you so much!
Thank you for the demonstration sir.
Sir, I have a question. How rejected electrons be replaced under photoelectric effect.?
The electrons don't have to be replaced - the reason they are being rejected from the plate is because the plate is negatively charged at the start of the experiment (at 0:54) which creates a potential in the plate due to excess electrons.
Just by looking at electron deflection behavior, arriving at particle notion seems very crude. Increasing the Intensity of the wave may not deflect electrons out of the metal, because electrons also possess wave behaviour. Electrons are particles with wave characteristics at the outskirts of their self spin. Although visible light may not deflect electrons out of the metal, it still energizes them.
Omg thank you so much for this video, it gets right to the point with a great visible demonstration!
I agree with TheSoundsage, can you please explain clearly why you charge the rod, then touch the zinc, then remove the rod. also, the first time the UV light is introduced, i didn't know where the lamp actually was, so i was surprised to see the leaf going down. the second time the demo was done, i saw the lamp well.
Sorry for this late reply. Bringing the positively charged rod close to the zinc plate creates a positive potential in the plate to which electrons are attracted (opposites attract.) He introduces these electrons by touching the plate with his finger while the rod is close. If the rod weren't there, the potential in the plate would be neutral and no electrons would move into it. He then, crucially, removes the finger before removing the rod. If he removed the rod first, the potential would go neutral again and all the excess electrons would flow back into his finger. Hope this explains it.
Thanks very much sir am a physics students but don't understand this until I came across your video 😂😂😂 thanks Prof
thank you such an impressive demonstration
Why is it that this phenomenon cannot be described while thinking of light as a wave.
Why is it that high energy waves can't knock electrons?
In the wave picture, frequency is not important. A wave of any frequency can have a large amplitude (call it brightness) and give enough energy to an electron to free it from the metal. But that idea fails, because visible light will never discharge the electroscope no matter how bright you make it.
"NCERT grade 12 physics part 2" pretty much explains it
Because this effect is not about energy, but frequency. From 430nm to 750nm there's visible radiation. Upper, is UV, and X rays, and last, Gamma rays. Independently from it's energy.
Drake Danos awesome explanation! However, why cant we just include frequency as a factor in the wave model, and say that in order for wave X to transfer its energy to an electron, its wave needs to be at least of frequency Y (threshold frequency). I still dont clearly see why a photon model should be implemented!
Joseph Farrell why cant we just keep the wave-picture by saying that the “ejection” of the electrons only depends on the frequency of the wave not the amplitude. While intensity only increases the number of waves/strings being released from the light source. Why is the photon-picture necessary?
Nice explaintation sir!!! I understood everything
عرض جدا جميل وبسيط وهدفه واضح وساعدني في شرح الدرس بارك الله فيك وجزاك خيرا
My physics teacher made me watch this…
Me too
me too
But he didn't do it for you? That's lame. ;-)
Great job.Simple and precise
That was really awesome! Thumbs up! Keep making such useful videos!
Thank u very much sir for this wonderful video
How u will continue to make this type experimental videos
At 1:04 why is the gold leaf still negatively charged even though the rod is away from it
the rod makes induces a dispersion in the metal and leaves. Positive charges get attracted to the metal and negative to gold leaf. gold leaf separate out due to the the negative-negative repulsions
Nice video and good demonstration, simple and give a clear picture to understand that complex theory.
*Photoelectric effect demonstration*
Teaching Post 16 physics? Exploring particle physics? Then this demonstration is for you. Alom Shaha shows how ultraviolet light affects negatively charged electrons on a gold leaf electroscope.
#photoelectric #particlephysics #physicsdemonstration #sciencedemonstration
How can we be sure that it's not discharging because the big metal UV light is near it? Similar to the rod but opposite charge?
Then, the lamp should do the job even if it is off and the gold leaves should rise again when you remove the UV lamp
I just found my school project!
Thank you
learned more in 3 min vs what my professor discussed in a week
His voice is soothing
A photon-particle's self-vibration ought to have nothing to do with its energy when impacting an electron. A light-wave on the other hand - makes complete sense that its small wavelength should effect the electron more than long wavelength.
Not when you take into account the amplitude of the wave
----I believe it is called the photo-electric effect , when a photon acts on a reacting electron , knocking it out of orbit , correct ?
How can an electron be forced out of orbit after being struck by a force without mass ?---
Brilliant sir ❤️👍
Hey!!...you have nailed it... 😍
Could it be that photons give energy, and this is what triggers the creation, hence, the release of electrons? An exchange of energy, instead of a particle colliding model?
It's not a particle colliding model that would be Compton's effect
What happens is that like you said about electrons receiving energy. There's no exchange the electrons absorb the photons and if the energy of the photon equal to or more than what we call work function (which a certain amount of energy necessary to extract the electron from the metal) it can "jump" outside of the metal. if the energy of the photon was more than the work function the rest is converted to kinetic energy and the electron can go on for a certain distance.
Studying this for my exam tomorrow!!
unfortunatly this knowledge won't help you in exams bruh
@@anshik.k.t it will
Thanks for the video. Need some explanation after reading throne of magical arcana webnovel.
Very good, brother.
thank you for this video! it helps a lot.
You are the best❤❤
Where do the ejected electrons go to? (What happens to them?)
Nicholas Shutt wow thanks a lot bro!
The discharge of the electroscope is not instantaneous. Does anyone know the underlying physics to explain why the leaf does not instantly drop? The number of photons per second incident upon the metal must be greater than the excess electrons on the electroscope.
you are the best one👍👍
Such an elegant video and very clear.
+1
So, The higher frequency of the UV light is increasing the rate of oxidisation, right? hence the importance of giving it a scrub before the experiment. That is how it is discharging. Could this experiment still work if the zinc plate was surrounded in a gas that prevented oxidisation?
As zinc absorbs UV light, so it is used in sunscreen, I don't see how this experiment confirms an interaction with a particle of light.
It's just a frequency of light is close enough to the resonance frequency of the zinc structure, allowing energy to be absorbed and increasing the rate of oxidisation.
I have a few questions
Why was it that you put your finger down to discharge the golden leaf and then put the charged rod back on it?
Also if you were to continue shining UV light on it why didn't the golden leaf apparatus get positively charged and so the golden leaf come move back out as electrons would have still be lost from the zinc plate?
Answer to your first question- To show us that the rod is positively charged which by induction makes the metal zinc plate negatively charged.(Rubbing it with that cloth makes it positively charged because the cloth is positively charged because of the fact that the negative charges are taken by the cloth by forcefully removing the negative charges)
Answer to your second question- Because light is not charged.After light removes all the negative particles aka electrons the zinc metal plate becomes neutral. And because light is not charged, induction or any other charge transfer does not take place.
HOPE THAT HELPED.
@@vibodhj349 No, the finger wasn't to show us anything. If there was no finger used, no touching involved, the the electroscope leaves just come back to their closed position. The rod negatively charged, when brought near the plate, the plate separates out it's species, that is the positive and negative charges, positive staying there, negative going to the gold leaves. Then he uses his finger to take all the positive charges via him into the earth, leaving a imbalance and a net negative charge on the setup. I took help from this video: th-cam.com/video/4UnggxPVCYw/w-d-xo.html for confirming myself.
do you understend frensh?
How much ionizing radiation were you exposed to during this experiment?
wtf like none
It doesnt prove photons r quantized but only proves electron orbits r freq dependent ie can be excited through resonance
Is it true that american army has photoelectron weapon that has an effect on brain?( x-ray laser capable of conveying electron )
Yeah it's called "the sun"
This is a great video !
He could have done a better job explaining how, without touching the rod to the plate the negative charge was transferred to it.
Charge was only transferred from the finger. The rod is positive, not negative. The rod being positive attracts electrons toward it from his finger into the plate, which is close to the rod. When he releases his finger from the plate, the electrons are trapped on the plate.
I don't understand how, if the perspex rod is positively charged, the induction and then grounding by touch leaves a negative charge in the electroscope. If the perspex is positively charged, bringing it near the plate should draw electrons into the plate, and then grounding it by touch should allow them to leave, leaving th electroscope with a positive charge. What am I missing?
I follow your nice demonstration. I get the photoelectric effect using zinc .
But, it is not being possible using Aluminum. I think, work function of Aluminum is 4.28 eV and for Zinc this is 4.33.
What may be the problem?
Please.
The problem is that aluminum in air is covered by a thick and very well insulating oxide layer. The electron simply can't get through that. One can probably prepare a fresh aluminum surface without oxide layers in an inert atmosphere and then it should work. It's a lot of effort for very little effect, though.
It finally clicked ! Thank you this helped me understand this important concept
Albert Einstein was the fucking man dude
Hell yeah he was
Can I do this experiment with aluminium foil electroscope?
Yeah you are right but Einstein was awarded in 1905 Millikan won the nobel in 1921 He thought that Einstein was wrong but he supported Einstein with his experiment which is about photoelectric
I certainly did not expect that accent!
sucker-berg..didnt expect that name
Thanks for this .
I think it is bit of misleading, the rod was originally negatively charged....otherwise you won't get negatively charged plate by induction
Perplex rods are positively charged by rubbing them with a cloth. You can look it up. The plate is negatively charged by touching it in the presence of this potential field from the rod. Electrons move from his finger attracted by the rod's positive voltage (because opposite charges attract,) and are simply trapped on the plate when he removes his finger.
Thank you for making things easier
I'm pretty sure he's incorrect at 0:55, the rod becomes negatively charged not positively charged.
Well for your kind information he is correct
@@joseph1391 I don't think he's right. The plate got earthed on the same side as the rod, so if the rod was positively charged and the touched place would be negatively charged, then when you touch that side, the electron will flow FROM THE PLATE TO THE HAND, therefor the electroscope would be positively charged as well.
@@yutong9127 The plate is never earthed. It is neutral at the beginning of the experiment (but that doesn't matter). The positively charged perplex rod creates a positive voltage field around it. This is what attracts electrons from his finger onto the plate, neutralizing the voltage but not the charge on the plate. When he removes the rod, the only remaining voltage source is the excess electrons that are now on the plate.
nice video!
Thank you! Actually makes sense!
Basically, UV light's proton has enough energy to release electrons, while visible light cant?
Depends on the material. There are materials that have a low enough work function to release electrons even when illuminated by near IR light.
No such thing as a proton, unless a single 360deg wave of RF is called a proton
@@kingcosworth2643 And there is the kid who didn't pay any attention in school. ;-)
It is called photon, not proton.
so clear! i finally understand
I was really thinking he's going to turn on the UV lamp when he brought it near the zinc plate XD
Great video 😍😍
thanks for showing demo for this experiment
What was the wavelength of uv light used
Awesome! Thanks for the share.
excellent video
So the zinc plate was positively charged.
He then bombards the plate with UV and it discharges the plate.
Where did the electrons come from?
The Zinc plate was negatively charged
1:50 OK, I did hear him say it has a negative charge.
From atom's shell. Energetic (uv, for Zn) photons strip out electrons of atom's outer orbits.
Great explanation . Thank you
Wrist check ?
then what is role of intensity in photoelectric effect and increasing the intensity why current increases linearly
+appy tappy Increasing the intesity of light does increase the photoelectric current as far as the frequency(and thus the Energy) of the photons is big enough to make electrons be emitted.If it the frequency is not big enough,there will be no photoelectric current no matter how much the intensity of the light will be
Increasing the intensity increases the no of photons and that increases the no of electrons emitted thus more current
still not makin sense
Can someone please explain how did the plate get negatively charged in the first place?
the ruler is positively charged after being rubbed so when it is brought near a surface (the plate), the electrons migrate to the surface as positve and negative attract each other. this is charging by induction.
The rod gets positively charged when rubbed. When he brings the rod close to the plate, electrons in the electroscope are attracted to the rod, which makes the plate negatively charged while the leaves positively charged. When he touches the plate, some of the electrons in his body move into the electroscope. This makes leaves electrically neutral. The plate is still negatively charged because of the positive charge of the rod. When he lifts the finger and then, bring the rod away, the excess electrons in the plate are distributed throughout the entire electroscope. This makes leaves negatively charged and rise.
A "By definition" assertion is not proof; I propose that energy is coupled into the valence band electrons via the incoming EM wave and by choosing the proper FREQUENCY an electron can be 'pried loose' (excited to leave) from the valence band.
I need a quick reminder on how the electroscope works :/
Excellent
Which wavelength of uv light is needed for this experiment to work?
(facepalm)
The non quantitative answer is You need a wave length shorter than the work function of the metal sample from which you are trying to knock off electrons.
From the wikipedia page on Work Function the value for Zn (Zinc) is 3.63 - 4.9 and the unit is eV. (Why the range????)
From the wikipedia page on Visible Spectrum the energe in visible light ranges from 1.6 (for red) to 3.26 (for violet) which is a bit shy of that required to liberate electrons from Zn.
So ultra violet with a wave length of just a bit shorter (rough guess of (3.63-2.26)/3.26 or 11% shorter) than Violet should do it for the zinc with the lowest work function.
Thank you. I was able to do the experiment using a UV-C light and aluminium.
"From the wikipedia page on Work Function the value for Zn (Zinc) is 3.63 - 4.9 and the unit is eV."
==Ok, let's calculate the minimum wavelength for the UV light required.
Convert 3.63 eV to J.
E = 3.63 eV * 1.602176565e-19 J = 5.81590093095e-19 J
Use E/h = v to find the frequency of the light
v = 5.81590093095e-19 J / 6.62607004e-34 J.s = 877,730,071,647,416 Hz
Let's convert that to a wavelength value with c/v = lambda
lambda = 299792458 m/s / 877,730,071,647,416 Hz = 3.4155e-7 m
lambda = 3.4155e-7 m = 341.55 nm
Thank u👍👍
THX
Is it just me or are physics teachers not very good at explaining things in class?
Like sometimes I don't understand anything that they've said but as soon as I sit down at home for a few hours to look at it myself or maybe watch a youtube video, I get it
i agree we suck...
Awesome