I've been watching so many videos on diffraction, and none of it made any sense until watching your video. Thank you so much!
@DrPhysicsA
8 жыл бұрын
+Bonnie Hines Thanks. Glad it was of some help. All good wishes for any exams coming up.
@tanagool
3 жыл бұрын
I totally agree and he used just High school mathematics
@iftakharalam1650
6 жыл бұрын
1000 respects and likes for your efforts, Thank you so much, DR.
@mysciencyvids413
9 жыл бұрын
5:17 anyone else see squidward? (Also this is best explanation of double slit I have heard, thank you so much)
@deadwombat1
10 жыл бұрын
I really like the way you do things sir. Almost anywhere else if you want an explaination they will use all sorts of different physics terms and logics like they were to explain it to fellow colleagues. Here it is more like you explain the things that we will need to know and if you use some difficult "big boy's" words you will make us understand what you mean instead of just let us fall off half through the video. I really think you sir have inspired a whole lot of people.
@vidarvergaard6375
9 жыл бұрын
Elegant and clear indeed! Repeating the argument from time 43:50 to 44:41 for the angle; N times delta, and the total E field is shorter than the deduction given from time 44:41 to 46:07.
@salaheddinesb7312
4 жыл бұрын
Thank you very very very very very ... very much Professor ! I think that this video is saving lives !
@andrewstallard6927
8 жыл бұрын
Great video I'll certainly be using this as inspiration when I teach these concepts to my students. This was by far the best explanation of diffraction that would be comprehensible to a high school audience.
@jomen112
7 жыл бұрын
Richard Feynman -make- (sorry made, he died 1988) some pretty decent (read: impressive) explanations as well. If you haven't watched them, I warmly recommend to check them out. (Search for 'Feynman lectures' on youtube).
@niladri4919
6 жыл бұрын
Andrew Stallard very true.. 👌👍
@TheAndresOpeth
6 жыл бұрын
I am only trying to understand concept by myself for curiosity not being a physics student and watching this videos is one of the greatest things that I have found on youtube, Thanks a lot for share your knowledge. I appreciate very much indeed. I would like that you keep posting videos.... Outstanding job. Congratulations.
@DrPhysicsA
11 жыл бұрын
I've done some exam questions in a playlist on my KZitem channel.
@Damhuis95
11 жыл бұрын
All of this was impossible in lessons until I saw your videos, very grateful.
@DrPhysicsA
11 жыл бұрын
Hear! Hear! Good wishes to you all.
@DrPhysicsA
11 жыл бұрын
Strictly, of course, you are right. What we are actually saying is that if you take any point on the screen, the two light rays which arrive at that point from the two slits are almost parallel. The difference in angle will be miniscule and will contribute effectively nothing to the phase difference between the two light waves.
@CCPlaetean
11 жыл бұрын
Wow perfect timing, I have an exam containing stuff on this in 2 weeks. You are a good man.
@ProfRoflWaffles
11 жыл бұрын
I literally covered this very topic in class today. Great timing for revision before exams in a few weeks! Thanks!
@DrPhysicsA
11 жыл бұрын
Difficult to run it in reverse since the screen in Young's experiment would need to be the source. And the source would need to generate waves which exactly matched those arriving at the screen.
@marathondude
8 жыл бұрын
Well explained. Very informative, thanks.
@ozzykris
11 жыл бұрын
damn you are good man !!!!!! thank you. you are the best. you are better than most of physics books. god BLESS YOU!!
@victorhugodass
10 жыл бұрын
The best lecture ever!
@1989ashok
6 жыл бұрын
thanks for explaining physics in such a easy way :) greetings from india
@DrPhysicsA
11 жыл бұрын
I am working on this now. Should be up next week.
@fattail95
11 жыл бұрын
You are a god among students! Thank you so much, you've helped me no end :)
@jeydelaguila618
7 жыл бұрын
Your drawings are on point! Thanks for the vid doc!
@amiin2147
11 жыл бұрын
thank you so much had a weeks worth of lessons covered in an hour :)
@DrPhysicsA
11 жыл бұрын
It obviously depends on how much of an error you are prepared to tolerate. Generally anything up to 5 degrees is OK. If you look at the sine and tangent tables for angles from 0 to 10 you can see by how much they diverge.
@DrPhysicsA
11 жыл бұрын
You will find videos of mine covering both these subjects. I dont distinguish between AS and A2 but you should be able to see which bits you need for AS.
@yosseftaieb1574
3 жыл бұрын
I DIDN't understand why if X=lambda we'll get constructive interference, but the waves doesn't cross each other?
@jfriz6900
4 жыл бұрын
This was great thank you, but I'm REALLLLY lost as to one of the proofs you gave. It seemed to me you gave the exact same proof for why waves at a given angle would CONSTRUCTIVELY interfere in a double slit, yet DESTRUCTIVELY interfere in a single slit. In that case why would there not be destructive interference with wavelets in the double slit?
@naveed3621
11 жыл бұрын
the lecture is very nice but just want to ask something which seems confusing. Super position tells that when ever two waves pass through the (same medium) at same time in opposite direction interference occurrs and the displacement of the resultant wave is the algebric sum of the two waves. when you were showing the two waves in phase while deriving n*lamda=dsinO. they were in phase no doubt but were parralel. How would they meet and produce interference? Please explain. this may be wrong. expl
@DrPhysicsA
11 жыл бұрын
n is the order of the fringe. eg n=2 means the second bright fringe from the central bright fringe. nλ=d sinθ is the fomula I derive. But if w is the distance from the central bright fringe to the nth fringe, d is separation of slits and D is the distance from the slit to the screen then w/D is tanθ, and for small angles also = sinθ. So nλ=d sinθ is the same as nλ=d w/D or w=nλD/d. Is that what you meant?
@RosarioLeonardi
10 жыл бұрын
dany pharel : Yes, you are right. You have to consider the distance of the screen to have the correct answere, but usually the distance of the screen is much larger than the distance of the two holes that can be neglected.
@Josimar.quimico
11 жыл бұрын
this video is very nice man, this part of physics is awesome and very important to me... thank you so much! :)
@JohnVKaravitis
7 жыл бұрын
Do you teach? If so, you must be a master teacher!
@aminamouhamed456
6 жыл бұрын
Hi. I have a question about that. On a diffraction grating why do we get an interference pattern with colours and not fringes with white light? Why at a certain d, light get spread out in colours and not in waves of monochromatic light? I can t visualize that, i know that it depends on d.
@danypharel3245
10 жыл бұрын
12:26 Question: I understand the two waves are in phase and will thus form constructive interference, but practically if the two waves are parallel then they will never meet to form a bright region?
@danideboe
8 жыл бұрын
Apparentely we have to assume that since they have the same angle
@christopherevansanders3629
2 жыл бұрын
Ok a photon has two parts the storage like a hard drive (the wave part of a photon) that carries the information (the particle part of a photon) of the object that emitted it or reflected it or observed it fully (which full absorbtion is no photon reflected back or photon empty of information reflected back equals black) so a photon leaving the source that emitted it is a wave with the information (particle) of the source it came from when that photon is reflected by on object part or most of the information from the source is transfered into the object and the photon reflected has a percentage of source information that is 49% or less and now has 51% or more information from the object reflecting it. So in the double slit experiment the method used to observe the photon shot before the impact of the back wall takes part or most of the information in it away which takes away the interference pattern and when the method used to observe the photon a second time replaces the information the first observance took out and now you get your interference wave pattern again.
@Nitish-Rathod
3 жыл бұрын
Hello i am from 2021 ❤️, where are you Dr. I also create like this channel #scispell You are superb
@ganiesuhailahmad9749
6 жыл бұрын
Hi,It was a nice lecture sir but at one place like Sin(N*delta/2) /Sin(delta/2) is actually when delta tends to zero the denominator term tends to (delta/2) but upper term will remain same due to N.Then,we will rationalization by N like N*[Sin(N*delta/2)/N*delta/2] as delta tends to zero Sin( theta/theta) = 1.
@Ab041071
10 жыл бұрын
Nice classroom discussion for the 12th standard students..
@Mrnobody893
11 жыл бұрын
I learnt so much from you!
@Hythloday71
7 жыл бұрын
What you call Huygen's source in this classical analysis is explained by the uncertainty principle in QM ? Is that right ?
@jomen112
7 жыл бұрын
Yes, it is another (classical) way to look at it. i.e. a particle interpretation instead of a wave interpretation. The problem with a particle interpretation is that it cannot explain the interference pattern when two slits are open, i.e. the prediction made by the uncertainty principle alone would be two large blobs, which is not the case.
@PrashanthAmbatimob
10 жыл бұрын
What happens at molecular level in the double slit experiment? Thanks,
@DrPhysicsA
10 жыл бұрын
For these purposes, nothing. Quantum behaviour is at a much lower level.
@DrPhysicsA
11 жыл бұрын
Thanks.
@theguitarway12
11 жыл бұрын
At 15:30 what does n stand for here? :) also is this the proof for the equation w= (lamda x D)/ s ... im doing AQA so im not sure if this is the same thing because we have to learn a proof for it...
@jananni123456789
10 жыл бұрын
even though they meet up at the screen do we presume the light beams to be parallel?
@DrPhysicsA
10 жыл бұрын
Yes.
@huntingresonance
10 жыл бұрын
DrPhysicsA Thank you for the video, I am a physics teacher and your videos always help keep me on track when something starts to get fuzzy again! In relation to the point that this user made... is it only because the angles are so small and similar that we can approximate the parallel lines to the actual lines? It seems that the angle each source makes is either slightly more or slightly less than that of the parallel approximation... so do these offsets effectively cancel? (thank you again... your videos are genuinely fantastic!)
@Gunslinger19911
11 жыл бұрын
As your videos make things so clear for people, could you please explain the "Delayed choice quantum eraser"? Please note that if you do, I cannot be more thankful than I already am for all your video's!
@blugreen99
Жыл бұрын
Delayed choice xpt debunked by Sabine Hossenfelder.!
@samridhmukherjee8489
9 жыл бұрын
Thank you so much! Your lecture made my concept crystal clear. But sir, with due respect, I have a question. In talking about the Single Slit Experiment, you showed that inference indeed does occur, which gives rise to light and dark fringes. But in doing so, the three waves you drew were parallel to each other and never seemed to superimpose, yet there was interference. Could you please clear this doubt of mine?
@dangiscongrataway2365
8 жыл бұрын
8:30 I was wondering if you say the distance is about the wavelength the wave will pass through, and wifi wavelength is 12.3 cm if my room was built by mirrors would a wifi signal be able to pass through a hole of 40 cm? What about 10 cm?
@gamingdust3r
6 жыл бұрын
it would be able to definitely pass through 40 without being diffracted. In 10cm diffraction would occur but it will still pass through
@seanki98
9 жыл бұрын
2:30 I thought for the experiments using electrons, the electrons would essentially interfere 'with itself.' Why is this not the case with photons?
@yskezocha
7 жыл бұрын
The electrons do interfere with themselves, and so does the photons. Any particle is localized in space in accordance to its wave function. So be it an electron, a photon or even a molecule (www.nature.com/nature/journal/v401/n6754/full/401680a0.html) when they encounter a grating such as the double slit, and no measurements are made to see in which grating the particle passed through, the particle interferes with itself giving rise to the diffraction pattern.
@yskezocha
7 жыл бұрын
cab I'm assuming you don't do physics. It's alright, it is hard to understand this concept at first. It is strange and it doesn't fit our classical model of particles. But by describing everything as a wave function, it shows that said particle has the ability to do all the things that waves do. I.e. Interfere, diffract etc. I will also mention this: quantum physics is NOT something we simply decided to do because mathematics said this was possible. Not at all. Through real life experiments, done on a daily basis, we developed the mathematics that fit to what we observed.
@yskezocha
7 жыл бұрын
cab perhaps I may have miss understood what you said. Perhaps you meant this to be a joke and I completely misunderstood. Although, the ragdoll part I still didn't understand. I do apologise. Still, I hope the original person will see the comments and better understands the concept of diffraction with matter :)
@yskezocha
7 жыл бұрын
cab again, I do not think you do physics. As I do understand what you are saying, and it is valid for someone who is new to this concept. Quantum mechanics does not come from theory. It comes from real life experiments. I'm going to stop here because because I think you now get the point, and I see yours. The only thing I can say is, go to your local science centre (or) go to a physics lab, and ask a physicist to set up and explain the experiment to you. And you could possibly even do it yourself if you are capable, which by the looks of thing you probably are since you seem to be quite sharp, just not well informed. As of 10th of June 2017, the physics I explained earlier, is the physics we understand and we have observed today. Maybe in the future there will be even crazier experiments, and more detailed, such that we can truly understand this puzzling place we call home. Until then, I hope you do do some research and find out more about this. Of course online is a great source but I don't think that would be too helpful for you since this video alone didn't help. Which is why I recommend you go and do it yourself! :)
@mollypete4270
5 жыл бұрын
Beautiful. Thank you.
@shivamdubey4783
4 жыл бұрын
hey man that was an awesome explanation crystal clear just one request sir can you plzz make lectures on quantum entanglment also plzz that would be really helpful
@maw-6479
10 жыл бұрын
I'm slightly confused in the derivation of the diffraction grating formula why "d" the adjacent side of the triangle wouldn't increase integrally like the path difference, as you move away from the central maxima?
@DrPhysicsA
10 жыл бұрын
d Is the distance between two consecutive lines on the grating.
@maw-6479
10 жыл бұрын
DrPhysicsA thanks p2 has been and gone now but your videos were of great use to me
@qualquan
5 жыл бұрын
Double and single slits well done but did not emphasise their contrastingly opposite equations for bright and dark fringes which are so beautiful. Also hinted but did not emphasize the Heisenberg effect of the widening of exiting beam as the single slit narrowed or light wavelength increased.
@hadrianuslau6390
4 жыл бұрын
Really understandable
@DrPhysicsA
11 жыл бұрын
That's right.
@timbekli4739
5 жыл бұрын
sir your series on QMs are fabulous and i want to thank you on that :) by the way on 10:15: the two waves should not be parallel y drawn. because parallel line dont reach. instead you should draw the two waves directing to the same site on the screen.
@mikeoxlong2077
2 жыл бұрын
Indeed they are not parallel, but because the angle is small , it is a good approximation
@andrewbaxter6242
9 жыл бұрын
I might sound stupid but can someone explain why n is one for the first fringe . Like how do we know it is one and not two
@augustomaeder1712
9 жыл бұрын
because the interference is maxim when d*sin(theta) = n*lambda, being n=+-1,+-2,+-3...
@firemylazer01
7 жыл бұрын
8:29 did you mean amplitude there rather than wavelength?
@gamingdust3r
6 жыл бұрын
no
@niladri4919
6 жыл бұрын
Where r u dr?? U had not uploaded any videos for last 3yrs....😟😞😭
@binnoypanicker3643
8 жыл бұрын
+DrPhysicsA Thanks so much for this explanation.
@DrPhysicsA
11 жыл бұрын
The general principle is that if you look at it, then the interference pattern will disappear.
@afsana9136
8 жыл бұрын
Great video! Just to clarify: what do you mean by "opening up the slits"?
@lekunberriko1
7 жыл бұрын
Very good, brother.
@Carlisle412
10 жыл бұрын
Fantastic!
@theguitarway12
11 жыл бұрын
oh so if the question said that it was the second order and not the central fringe then i would use say n=2 instead of n=1 when doing calculations? :)
@fadiabu2184
9 жыл бұрын
Amazing Video
@Mrnobody893
11 жыл бұрын
Thank you
@seanki98
9 жыл бұрын
24:16 Isn't this also explained by the Heisenberg Uncertainty principle?
@PR0Z0MBIE9877
7 жыл бұрын
At 13:00, how does the crest meet a trough? The 2 waves are traveling parallel and they don't seem to be overlapping.
@jomen112
7 жыл бұрын
The example is a model to illustrate a method how to reconstruct the the interference patter given the distance between the slits and a wave length. As you are aware of, the overlap (interference) occurs in the plane and what DrPhysicsA shows is that you only need to know the distance between the slits and the wave length in order to calculate the interference pattern. In other words, if the distance between slits is known, you can infer the wave length by measure the distance between the crests. Which is in principle how the de Broglie (matter) wavelength of classical particles like the electrons and atoms can been determined. Or if the wavelength is known you can infer the distance between the slits by measuring the distance between the crests, in other word you can in principle determine a crystal structure (3D) from an interference pattern (2D). And if you turn that the other way around you have just created a hologram...
@PR0Z0MBIE9877
7 жыл бұрын
Thank you for the nice response brother. I appreciate it.
@theguitarway12
11 жыл бұрын
And also when do we know not to use the idea that tanX is the same as sinX as in what angle would it have to exceed? :)
@flylikeg6
6 жыл бұрын
When someone talks about waves, how should i have to visualize it? While graphing waves ,i simply draw some oscillations or (crest and trough )thing while i don't know what they actually represent.All i know is waves are some sorts of disturbances that carries energy. Are waves just abstract or does those crest and trough even mean something? If they mean something what the mean position actually means from where their amplitude is measured ? I just don't get this concept .Are waves (some kind of energy fluctuations ) just hypothetical ? Even the wikipedia's definition sounds so strange? I'm so blind right now unable to get any insight about it .It would be very kind of anyone who could explain this to me intuitively .I know i 've been terribly missing something ..please help
@daepicadam7358
6 жыл бұрын
This might not help but since there was no reply to this I thought I'll give it my best anyway. I think a lot of the time a wave just represents a probability of where a particle may be. For example, with an electron, it is simply a wave of possible places that it may be because it's not actually in any one place. If something is not in one place then it can be described as a wave I guess. I don't know.. that's how I think of it - a wave of probabilty. Ugh, looking back at this it probably won't help but ehhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhh shoot me
@daepicadam7358
6 жыл бұрын
I'll also say that the higher amplitude of a probability wave, the more likely you are to find the particle associated with the wave there.
@RascoH12
11 жыл бұрын
Good day Sir, What if incident light source comes in an angle of lets say 45°? How would the fringes pattern present? I have an idead but confirmation about this matter wouldbe great. Very nice video and thanks for uploading it.
@MoonLitWarrior
11 жыл бұрын
Can you do a video on quantum teleportation?
@freddiepowell8524
10 жыл бұрын
5:21 = a very odd and startled looking face!
@supercoolmy
11 жыл бұрын
Does someone notice, What i noticed??? Its a face with a normal expression at 5:17 (by ignoring the arrows and the crest and troughs (ON SIDES)....:)
@fathihosseiny7450
7 жыл бұрын
thanks for this amazing video how can i prove hesinberg principle by compton and double slit experiment
@jomen112
7 жыл бұрын
It can be proven by showing that momentum and position are Fourier transformations of each other. Not sure, but I think Leonard Susskind have pointed out this relation in his Stanford lecture series.
@kanck7909
6 жыл бұрын
very helpful
@heathermorley8329
11 жыл бұрын
Just realised I've never done diffraction gratings and the aqa book is no use at all. I feel failure approaching
@manuelvillarreal837
10 жыл бұрын
Ha ha ha just noticed a face at 5:43 lol
@StephenRayner
10 жыл бұрын
Well done sir, I'm glad you are picking up on the geometry.
@theguitarway12
11 жыл бұрын
Sir could you pleeeeaasssee make videos covering AS topics mechanics and waves Great Videos! :D
@kurdman12345678
10 жыл бұрын
This so hard and my exams on Monday :(
@DrPhysicsA
10 жыл бұрын
What level exam are you doing. This is more complex than A level. For A Level, this might be better Wave Particle Duality - A Level Physics
@kurdman12345678
10 жыл бұрын
Im doing AS aqa physics unit 2 and thanks for link
@DrPhysicsA
10 жыл бұрын
kurdman12345678 You're welcome. And here is the link to my A Level revision playlist which covers both A2 as well as AS. kzitem.info/door/PL5D99A319E129A5B7
@defleppard6315
10 жыл бұрын
dud u r the best , thnx !!! and now because of u I think even farther ,,,if we could align all our sinus waves from our eyes or unit\synch' them somehow WE COULD SEE OTHER dimensions(or demons :) !!!! holy shhhh !!! i'm guessing ,, WE ARE SO BLIND !! relatively !?) maybe god's trick ? :)>>>
@flylikeg6
6 жыл бұрын
def leppard you alive now???
@MilitanT07
11 жыл бұрын
can you please cover more Einstein time stuffs.
@qualquan
5 жыл бұрын
diff grating begins @25:30
@shabana4980
8 жыл бұрын
is this for cie
@DrPhysicsA
8 жыл бұрын
+shabana syed naveed My A Level revision playlist is a set of videos intended for CIE, AQA, OCR and Edexcel. Not all videos are relevant for each syllabus.
@MellanieBlast
11 жыл бұрын
What will we see, if double slit experiment is photographed by the trillion FPS camera developed in MIT ?
@fenerbahce262
11 жыл бұрын
@drphysics Sir could you please go through some past papers please exams in 5 days The exam board is OCR A
Speaking of Huygens, apparently the Dutch pronunciation is something like "hahuns".
@kaadshah7737
9 жыл бұрын
haha..h nd y r silent when we speak huygen...is it??
@danideboe
8 жыл бұрын
The uy sound and the g isn't the same as in english. I'm a native dutch speaker
@Ash-mf9rz
10 жыл бұрын
Hi Sir. How is this video different to your video on waves. I would watch this one hour video but i'm running out of time for exams. I just want to make sure that there is not important content being missed. DrPhysicsA
@gingermanbread2000
10 жыл бұрын
There's an owl at 5.05
@giakon1
4 жыл бұрын
the explanation is not rational. the assumption that the 'light', the intensity of light on the screen, is because the light is a particle (a solid corpuscle, an object) and a wave (a concept, what is waving?), is very wrong; and this bring the author of this video to the wrong explanation and of course the conclusion.
@blugreen99
Жыл бұрын
9
@maximusprime98
11 жыл бұрын
Let me guess you're all here because of tomorrows exam. Good luck to us all
@whatseveryonelookingfor7023
3 жыл бұрын
Today’s!
@PureOriginz
10 жыл бұрын
C'est difficile
@DrPhysicsA
10 жыл бұрын
See my reply just below. If you are doing A level or equivalent you would be better with Wave Particle Duality - A Level Physics
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