Single slit interference | Light waves | Physics | Khan Academy
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- Опубликовано: 6 окт 2024
- What happens when there's only one hole? Created by David SantoPietro.
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![Single Slit Diffraction [AHL] - IB Physics](/img/1.gif)
As representative of the state general of the Dutch royal democracy I hereby pardon your mispronunciation.
Loal
Lol
Lolol what even
lole
Lol 😂
You made single-slit and double-slit diffraction easy to understand and now I am not panicking over physics anymore, you're the true og, my good sir.
indeed
THANK YOU, why isn't Huygen's principle taught BEFORE two slit interference in all the texts, you'd think this knowing this beforehand would save you from a lot of misguided connections.
milkwasabadcholce because it doesnt have anything to do with the doubleslit experiment. Different causes..
Kim double slit interference involves the interference of two point sources. Single slit interference involves the interference of an infinite amount of point sources, and defines diffraction: they are definitely linked.
science is all about being hard ;)
in india huygen's principle and wave nature of light is taught first and then we move onto young's double slit experiment.
@@REVIEWSGALATTAyea exactly, its taught before and tbh it caused SO MUCH confusion, i have been stuck on it for a day 🥲 i was trying to find a connection bw huygens and double slit and obviously got more confused
😭😭I wanna cry coz I still don’t understand this
Please refer to " Science Alert, current research in Physics".
i like how he didn't ask for a like and sub in the end and simply said "you're all good"
Ahmed Ibrahim which deserves both a sub and a like
Because it's Khan academy
That is called nonprofit organization...
This concerpt never made sense to me until I watched this video,,, thank you a lot for the lesson
if huygen's interpretation was taught to me before geometrical optics I'd be an astronomer/photonicist. It's such a leap from too simple -> crazy, to weird -> everything become simple
So let me bring to your attention the elephant in the room.... What are the light waves refracting THROUGH?? The universe is pretty simple when you think about it and don't overcomplicate and keep bombarding and bamboozling teenagers with complex formulas and experiments that are just the same as magic tricks (smoke and mirrors) . Thankfully I managed to see around the slit as it where 30 years after being brainwashed😁 n.b. I have left a few comments under single and double slit experiment RUclips videos that have questioned the narrative and all of a sudden I am now not allowed to post a new comment, just reply to one?? ..I must be onto something 🙄
Its so stupid my testbook tells me nothing like this and expects me to understand. As others has mentioned you are a hero. its so easy to enjoyable to learn with your videos. thumbs up
Same my book is also doesn't explain this topic well..This vedios explain it in detail
4:53 Engineers approximation: 8≈∞
hahaha
Geniss i mean genius
I mean I'm drunk
The ONLY single slit diffraction video that’s actually makes sense. Thank so so so much Khan Academy!! Saved my A level!!
Your videos are absolutely brilliant! Excellent job and thank you for making this topic so clear and visual!
Twhen my school teacher taught me this, i was unable to understand it, but with your explanation i think i understood it just fine.
THANK YOU,
Very interesting, especially for a lay man who has been told so many times that only a double slit will show interference, thanks to quantum mechanics...
By the way, your pronunciation of Huygens is quite good if I compare it how 't Hooft is sometimes announced on RUclips. :-)
Fransamsterdam in your comment quantum mechanics solved the main question Hahn that each point acts as a wave thanks........
Can someone please just make a playlist of all videos by David SantoPietro. That would just make life so much more easier.
one of the best explanations of single-slit diffraction. good job
I have never had such a strong sense that something is wrong
Omg you are a life saver ❤️... thank you very very much. It solved all of my questions which I posted in double slit experiment video regarding if the wave spreads out does that mean wavelength of that particular wave increases?
You made this critical topic easy to me. Thank you so much sir. Lives in Bangladesh 🇧🇩
I had to watch this 3 times to finally get it
Khan Academy....The Savior
thank you .... now i understod that.... that was killin my brain for years :3
omg, what a good way to explain it visually, exactly like how i like to learn physics. THANK YOU
Why are we only considering the points spaced w/2, w/4, w/8 apart? Shouldn't we be considering each pair of points instead since they each would contribute to the intensity? Also, it seems like even if the w/2 cancel because they are half a wavelength apart, the points w/4 apart wouldn't cancel because by definition they must be less than half a wavelength apart so I don't see the logic there at all.
thank u thank u the first sentence that u said is why I'm looking for this in the internet I was so frustrated that all the books I have were talking about waves interfering with out telling me why they interfere in a single slit in the first place
Finally! Thank you for your amazing explanation. Absolute legend.
This has bothered me for a very long time. Thank you very much for this video. Great explaination! My very minor criticism is when you say that the wave cancel completely at that point. Later, you explain that there is a slight difference [in the length of the triangle]. At that point you could add that’s why they don’t cancel entirely. But, I wouldn’t redo or add to the video if it changes the duration google posted as it gives you precidence! Again, great job and thank you for bringing up Huygen’s! - Jim Foit
I don't know if i have got it right but, the way you cal the different wave lengh as w/2*sinΘ confuses me,because the right part of light from the footprint seem to have different wave distance
I understand your explanation of single slit diffraction of light and the production of small maxima either side of the big central maxima. However, whenever single slit diffraction diffraction is set up in a ripple tank there is no sign of the small maxima either side of a central maxima.
Straightforward,pure teaching
Thank you for this precious resources for the students
Nice 😊
This just motivated me alot to learn physics:D
How is 5th source w/2. If there are 8 sources than the 4th source should have been w/2.
this is awesome I wish someone could have taught like this to me earlier
I was so confused with this equation that path difference of minima is getting for constructive. Thank you for video
Thank you so Much!!! The start of the video was exactly answering what I was looking for I had no idea their was so much more to it
I'm going to be very nitpicky: his full name is Huygens, with an 's' at the end, so it's actually 'Huygens' principle'.
'Huygen's principle' would suggest his name is 'Huygen'.
The pronunciation is acceptable: I can't think of an English word with the same 'ui' sound, even the 'RightSpeech' video on RUclips does'n get Huygens name right...
Nice video BTW...
Why are we taking the topmost and middle point of the slit to get a dark point? How do we know?
Ya I don`t get it either. He said "if it's destructive at half the slit length" and proceeded to make that scenario the official formula
@Ryana Imtiaz
He took the "topmost" and "middle" point, only for the sake of explanation. But this applies for any two arbitrary "points", as in reality, there's an infinite number of "points" within the band of light that passes through the slit, where you can't really select "points" that are "topmost" and "middle", as concepts like "points" are just an approximation...
@@D8Football actually, it isn't the "official formula" but more of a presumption made to help find an explanation to why it so, i.e., why there's a dark region between the bright ones.
I don't know why but I never seem to understand Kahn Academy. It seems like it should make sense (especially compared to my teachers) but it just goes in one ear and out the other.
Doubt: what if we took 9 sources(as in odd sources) instead of 8, wouldn't there be further complications with deciding whether it ends us up with constructive or destructive interference ? Kindly respond.
Well then are there no troughs??...u can keep zooming in and all u see are wave fronts??
How does infinitely many diffracting waves make a ‘full’ wavefront before the slit then? Why does the slit make the infinitely many diffracting waves into an interference pattern not a ‘full’ but smaller wavefront?
I guess I understand that the slit can make a interference pattern but why doesn’t it do the same thing for a normal wavefront?
Terima kasih, materinya sangat bagus
Good explanation. Thank You..
I don't know if i should be happy or disappointed at myself because I'm not upset about anything lol
Brilliant...thanks a lot🤗
This helped a lot.
please make a video on maxima minima and everything please?.
path difference for destructive points is (2n+1)*half lambda,so in this case why is asin theta=n*lambda not asin theta=(2n+1)*lambda
umm shouldn't this be called single slit diffraction?
Technically, it should be single slit diffraction AND interference. Since, even in YDSE, the waveform diffracts and spreads through the slit, the key really is the interfetence which occurs.
In india it is diffaraction lol
are you dumb? there is no medium change so no diffraction. you must be braindead ffs
@@yaoooy are you confusing with refraction?
@@yaoooy Diffraction happens in same medium. When medium changes, it's refraction.
yes but when you make the middle of the slit half polarized then they should not interference with the other neighbourhood. also the cancellation is must happen at the slit point only. its not really like a lake of waves.. once it cancells its done, that wave wont de-cancell due to phase swap.. thats why when u move the wall back and forward, you dont see alternating blobs that would represent the peaks and destruction points intersecting the wall...
Omg hyungugons thing is cool
Great video ! Very informative !
Just one question , how is the difference between the two arbitrary points chosen , w/2 ?
Anubhav Bahadur if you calculate it comes out w/2.
There are 8 points hence the distance between two consecutive points is w/8.
The points he chose had 4 points in between.
Hence, the distance is 4*w/8 = w/2
Actually it's not arbitrary, you set and divide the slit line up in such way that two points superposition cancels and things pair up.
@@papiyaghosh102each two pairs cancel out assuming slit is very small right?
Well explained, thank you. Question: if hyugen's principle is true, how can you direct any light at a particular direction, for example a pointer laser? Shouldn't any light source always be a source of spherical wave fronts?
That are polarized light
I think it's because Laser light is collimated which means the light rays are all parallel so, it spreads very little on it's journey.
@@ht-ve9fe ok so would agree then that hyugen's principle in fact is not true?
@@johanneskrv No I wouldn't because after certain distances lasers do begin to diffract. Other than what I need to know and the brief information I have read, I am not really in a position to comment whether he is right or wrong and he more than likely has greater understanding of the subject than you do and certainly more than me. However, from what I've studied, nothing disproves and there's plenty of people who have devoted their lives to Physics and even this topic which I am sure would have been disproved by now if he were to be wrong.
@@ht-ve9fe i'm not saying he is incompetent. Just wondering why in some cases the hyugens principle seems to be in effect and in others not. This seems contradictory.
wonderful explanation💥
At the centre of the screen, there is zero path difference between each pair of sources and they interfere constructively . But the resulting phase of each contructive interference isnt necessarily in the same phase isn't it . That means the centre of the sreen which we see much brighter shouldn't be that bright.
The diagram is so damn satisfying! 😬
I know this is weird but it is (to me) 🙄
weird*
This man is speaking the language of gods
If all integers give destructive, what gives constructive besides 0??
When path difference is an even number of half wavelengths you get constructive whereas an odd number of half wavelengths gives destructive.
Thank you sir you really give a very nice and simple explanation 🙂. Sir is it possible to also add mathematics of diffraction also
Im living for your "w" prononcuation, cuz its so cute
How can we be so sure that destructive interference will occur at those specific points like if the waves from the uppermost and the middle points interfere destructively at that point then it could also interfere constructively with the waves from the other points .... And why should we take half of the slit and not the full one ??? They are just ripping my mind @part!!!
Sheraz Khan experiment
For a destructive interference to happen, all the waves have to cancel out - the sum of their "heights" has to be 0.
That means that for every wave with height y there has to be a wave with height -y at that point we are looking at.
If it were otherwise, all other waves would cancel out and that wave would be "left alone" so that point wouldn't be a dark spot, the sum of the heights would be equal to its height = y.
So whichever way you add the waves, you should always end up with the sum = 0 for it to be a dark spot.
for example lets say you add up separately waves with positive heights at that point in a specific time, and separately the ones with negative heights then. lets say the heights are y,x,c,v,b... and -y,-x,-c,-v,-b... or what ever names you want to call them. The sum of the positives is y+x+c+v+b+..., and the sum of the negatives is -y-x-c-v-b.... and the ULTIMATE sum is (y+x+c+v+b.)+(-y-x-c-v-b...). As you can see whatever the sum of the positives is, the sum of the negatives is always - that, so the sum is always zero for that point. So pairing off the waves is just editing the sum (y+x+c+v+b.)+(-y-x-c-v-b...) to y-y + x-x + c-c + v-v + b-b +...
(You must note that the heights of the waves are dependent on time so when I say that a wave's height is positive I mean its positive in a certain moment in time, not always, same for negative).
You might ask well how do bright spots appear then.
Well for bright spots at a specific moment there are more "positive" waves than "negative" ones, or vice versa, so not all of them cancel out, and thus the sum is not equal to zero and there is a constructive interference.
Hope this helped :)
IKstreme Yeah that was a great explanation . But what I am thinking is that why should we apply plain Mathematics to it .... If I apply some logic , what my mind says is that there shouldn't be any destructive interference . Like , for example all the waves arrive at the same time ... You said there will be y for -y and x for -x and so on . But let say the y . Thus y could also be in destructive interference with the x wave or -x or what else you call it . Then , why should we add up the two y's (positive and negative) . Now you might say that x and y can't be added because they are different variables but let's forget about that because we don't have an equation like that . It could be numbers and then numbers could be added in any way . What my concern is that why should we be adding two waves from two distinct points while there are waves from numerous and numerous points . Based on your explanation , I think when we add them all together we won't be getting either a constructive or destructive interference anywhere ...There shouldn't be one of them.. I hope you get my point.
if y and -y are in a destructive interference, and y and -x are also in destructive interference, then so are x and -y, so any way you pair them up the total sum is always zero:
(y-y)+(x-x)= 0+0 = 0
(y-x)+(x-y)=0+0 = 0
Even if you add waves that are not in destructive interference the total sum will be 0. lets say y+x=a, then by simple maths (-y) + (-x) = -(x+y) = -a.
So even if you do:
(y+x)+(-y-x)=a-a=0
you still get zero because ultimately they somehow all cancel out
IKstreme Ok it makes sense but I am still very much confused . I am just thinking that how can there be + for every - when the waves are pointing at a point far away from the central point ?
Love ur teaching skills🤘❤️
God bless you Sir
This is easy to understand. But what confuses me, is when two waves that run along each other completely PARALLEL and apparently never intercept each other can interfere with each other.
it is pronounced "Ha-hen's principle"
Not sure if this counts but I have a growing light for plants. Unintended experiment. There is a small single slit where light breaks through. I get 4 single strands of light in a tight angle, Red, Purple, Red, Purple.
What the heck is going on here?
Edit: Ah I get it, now, the edges spits the light. 1 edge, two beams. 2 edges 4 beams. I've never seen this before, I was just mindblown how it could happen without trying. Perfect conditions.
A true lifesaver
I could be wrong but Im shore the angles wouldn't be the same
Aweri Blakely You are correct. The angles are very close/ approximately the same if the distance to the wall is much larger than the width of the slit. This is often the case, but he should have mentioned this approximation. Good catch!
Andrew Stuhr Haha I stopped too quickly to reply. He does mention its an approximation.
Huygens principle is actually like having infinite slits and getting a uniform pattern because infinite points on wavefront form infinite wavefronts . may be!!
Wow thank you!
thank you!
It is wrong .. You must divide it into odd no.of wavefronts so as to have a central wavefront ... How did you explain in 5/8 and 4/8 parts
Indian kids can't accept a different explanation from a different point of view for the same theory mate
Don't you put a convex lens at the opening of the slit?
That's how it's explained in my textbook
So, a wave front is a full constructive interference ?
It's like single-slit interference is like an infinite-slit, continuous version of the double-slit interference, I guess
How come the points on the end of the wavefronts don't spread out as there's no point to one side of them? Also, when the wave meets a slit, how come the points next to the barrier on the reflected wave diffract, for similar reasoning as above?
ya it's nice
thanx sir
2:11
is really cool and "UGE"
Don't understand why Theta remains the same at all point pairs surely it must change enough to make a difference. When the wavelength of light is in nm, (really tiny) a miniscule change in Theta would move the point from destructive to constructive.
If single slit can produce interference why don't we consider it in the ydse
Why we consider slit in the ydse as point sources and works on only interference of that pattern
Brilliant. But puzzled by why the interference pattern is always horizontal. If Huygen's is correct then shouldn't there be a spherical pattern?
Or... What if there was just a small hole instead of a slit? What would the pattern be?
If we make a small hole, then the pattern is, indeed, spherical. It's called an Airy disk.
Please refer to " Science Alert, current research in Physics".
Huygen is "HOW-chen," with 'ch' pronounced as in 'loch."
Walter Lewin said "HHURRHENNS"
what if you choose two points that are not w/2 apart? like two points that are right next to each other .
Can you tell me in which video you derived dsin(theta)=delta x?
Thanks, man.
I am the best in my physics class! lol
I was wandering what is wsinD= wavelength but i had figured it out at the end of the video which is AX÷D = wavelength
what about shooting one photon at a time? why will there still be an interference pattern?
oh my god u saved me thank uuuuuuuuuu
For once in my lifetime I was proud of myself for being clever but then "Ah! Not really." 14:14
What if I pair up topmost and bottommost point ???
1 and 8 pair constructively, rest pair up somewhat between constructive and destructive. However the 4 resultant waves have different phases and when they are added up, resultant will still be 0, albeit by applying more complicated mathematics.
It's actually fairly simple when you think about how interference occurs.
It's addition that causes constructive and destructive interference, so its almost like doing this:
1 + 1 + 1 + 1 - 1 - 1 - 1 - 1 = 0
I am trying to simplify it with a really dumbed down explanation, but the concept is pretty much the same.
His pairing is pretty much doing this:
(1 - 1) + (1 - 1) + (1 - 1) + (1 - 1) = 0
There are no changes to the results, it is rearranged in this manner purely for explanation purposes.
Leyton Zhang holy shit u just cured my brain cancer gj broo
so in those double slit interference video, why do they keep saying only one band of light pattern is observed when light goes through single slit as compared to interference pattern of double slit?
It was nice playing that game to obtain wsinΦ=√\
Cool video
Dosen't Huygen's principle glorifies presence of ether ???
Which app you use for this demonstrate
how would you explain that wsinΘ=4Λ for 4th destructive point
Why (m)th point only interfere with the (m+4)th point ?
nice