Young's double slit introduction | Light waves | Physics | Khan Academy

[@ThatDudeEddiee0]

I spent 1 hour in lecture and 1 hour in lab and was so confused as to understanding the constructive/destructive interference, the first minute at 40 seconds answered just that. BIG THANKS.

[@Mukeshkingzz]

Can u tell me definition of constructive nd destructive interference...🙄

[@IdunRedstone]

@@Mukeshkingzz When waves of same kind in cross they combine to make one wave at that point. Like if a high water wave went into another higher one it would be higher at the point they cross because the water is being lifted up by both. Constructive is when the waves add together to make a bigger wave. [aka when they cross you add amplitude together]. However if one wave was in the other direction (negative) to the other (positive), if they were at same height (amplitude) but in those opposite directions they cancel out so there is effectively no wave at that point. That's why it's destructive. Constructive and destructive usually mean where the waves are either crossing at max height in same direction (constructive) to make new one double the height, or they are same but opposite direction so completely cancel (destructive).

[@KibyNykraft]

Everyone seems confused... Why is there no interference pattern on the first wall? How do we know the photons pass gently uniformly through the next wall slits in the same manner as through the first? Let's follow the classical mechanics here of early Einstein and of the the classical physics, assuming that the photons are discrete pieces of matter : Once they enter through the first slit from the candle or lamp, there is a second wall with another slit. It is only needed a small discrepancy from the light path to create an interference pattern on the wall number 2. What the case was in Young's early experiments inspired by Huygens who of course understood that there had to be an interference pattern, was just that he assumed that photon rays would pass uniformly through all slits. But that we don't know just out of nothing; it only takes a small variation of the light path to hit the sides of the slit in the next wall, meaning there will be small pattern of interference. Some of the photons would reflect from off the back of the first wall, already having a changed path while or if going through slit 2. And so forth and so forth. Aggregated with the already discrepant variation from the main ray. Thus it has to be a wider and wider pattern of interference.

[@CorisWorld404]

Beyond incredible instructor!! He not only explains the right way but also shows you common misconceptions to avoid.

[@muhammadtouhid998]

first time in my life, i have realized what the circular form of wave representation means, all after passing everything, huh

[@sahilyadav3783]

xD

[@akshayjagtap9338]

Exactly bro

[@nisha1180]

True

[@ishantripathi9707]

Oh boy! Oh boy! Oh boy! Man you explained the concepts so clearly and simply. Hats off!

[@johnparks6936]

I went through so many videos... And this one finally did it for me!! Thank you so much. Here's what I couldn't understand: why were they showing waves as propagating lines when, in reality, they were like the sine and cosine waves with peaks and troughs? This videos answered that question and even explained where they would interfere constructively and where deconstructively, Beautifully explained!

[@MrWolfchamp-xi3cu]

Didn't work for me. Still don't know what destructive interference is. Can't even find any real life examples of it. Just never see it happen. Waves don't cancel, PERIOD. If i turn on two flashlights i just get more light. If i turn on two radios i just get more sound. NOTHING EVER gets CANCELLED!!!!!

[@OmriToren]

you're doing it wrong! you need one source of light (1 flashlight, radio, sun,...) and a screen with 2 slits on it (hence the name Double Slit experiment!) if you display that light onto a blank screen you'll see interference patterns! this wikipedia picture shows it animated upload.wikimedia.org/wikipedia/commons/3/33/Doubleslit3Dspectrum.gif -- if you don't understand the physics of it, look at the philosophy behind it! i find that easier to understand!

[@MrWolfchamp-xi3cu]

The interference is those blue dots on in the green of the pic right? plus what is the philosophy behind this?

[@OmriToren]

yes! the blue would be the perfectly destructive interference (two troughs) the yellow would be the interference of one peak and one trough (+1 + (-1) = 0) and the green would be the positive peaks of light! the philosophy behind this experiment is thomas young trying to prove that light is a wave based on his experimental results. his argument is as follows: if my theory is true (A), then when i set up my experiment i will see the results that I expect (B). he does see the results of (B), therefore (A) must be true! this is a philosophical fallacy that results in his theory being confirmed (not proven) and is called affirming the consequent

[@MrWolfchamp-xi3cu]

One peak and one trough? No idea what that means. If the blue is the destructive then that means that yellow is constructive right since its brighter that green and blue?

[@AlonePlaying]

Dude, i'm from Brazil and I'm really thankful for this video. I wasn't understanding a bit of what my college's teacher was saying, you'll save my exercises. Keep doing a great job!

[@annearts5]

U learn that in college?? We have this is 12th grade in India.

[@stay489infinity]

Bro, that's also collage LOL

[@TheGatoroberto]

Thanks ,good video and made very clear ... probably the easiest and most understandable explanation that I have ever found about this experiment

[@mugdhorozario4785]

Sir , The explanation enhanced my understanding. If I didnt watch this video , I would have lived under a rock with thousands of confusions So sir, I would like to thank you and would encourage you to keep up the good work for us , students.

[@fluffzxx9615]

Sar, full support sar

[@ihaveagoal4665]

@@fluffzxx9615 wow how funny, what a subtle racist remark to a student who is just appreciating a teacher for teaching him a concept

[@fluffzxx9615]

@@ihaveagoal4665 seethe harder

[@delusionalplatonist6077]

@@fluffzxx9615 you're sooooo funny bro 🤣🤣🤣🤣🤣🤣🤣🤣🤣🤣🤣🤣🤣🤣🤣🤣🤣🤣🤣🤣🤣🤣🤣🤣🤣🤣🤣🤣🤣🤣🤣🤣🤣🤣🤣🤣🤣🤣🤣🤣🤣🤣🤣🤣🤣🤣🤣🤣🤣🤣🤣🤣🤣🤣🤣🤣🤣🤣🤣🤣🤣🤣🤣🤣🤣🤣🤣🤣🤣🤣🤣🤣🤣🤣🤣🤣🤣🤣🤣

[@amartyachoudhury8991]

Beautiful explanation.... especially that part where you explain how the wavefronts from the two slits interfere constructively or destructively; and finally on the screen... very helpful; thanks a lot

[@barbros2023]

Already 2 mins in and I've learnt more than weeks of school. This teacher also doesn't sound boring and monotone. 10/10

[@aishwaryagorti8412]

This really helped me to understand what actually happens in the experiment... This was so helpful. Thanx a lot

[@DeuceBoots]

"How 'bout the destructive points?...shoooot, you know how to do that. These are gonna be the half wavelengths." Love it. Thanks again Khan.

[@ydkathy5771]

ur ten minutes have covered the content that my teacher spent classes talking about with clearer explanation. Thanks a lot :)

[@majsterektv7528]

I just relized my teacher is useless as I always heave to learn from the internet

[@96mohormukherjee56]

Hahahaha same @majsterektv

[@e0413836]

Not sure it's the teacher's fault - realized and have! Oh there is only so much that can be built from the basic lego kit.

[@praharshsingh2095]

i dont even call my teacher a teacher

[@cnu9948]

Its your fault first did you ask the teacher or not

[@litinggoh1169]

​@@cnu9948 Maybe he asked his teacher, but his teacher doesn't even know how to explain / explain in a way that's to difficult to understand / repeat the same thing that's mentioned in the textbook. Because that's what my teacher does. KZbin is much better than some of my teachers to be honest.

[@KashafNaeem.]

Thanks this was first video i saw in this chanel and was good not boring

[@benisman]

This has been really helpful for my A-Level studies, thank you so much. I finally understood how to implement the constructive and destructive interference pattern formula w=λD/s

[@maazali9456]

seriously i just understand the whole concept thank you very much.GOD bless you

[@MahmudHasan-pg1pt]

yes the best explanation i have ever seen, and i also understood my school teachers are so dumb to make us understand such nice topic

[@melynx1159]

This helped me trillions! I learnt in roughly 10 minutes what I struggled to understand in hours of lectures. Thank you so much! ❤

[@Creativekid-14]

Omg! My Clarity level reached peaks🤩 You are just amazing sir 😍 Thank you so much for helping me to understand beyond my textbook 🙏

[@annearts5]

4:12 he didn't have to join all the dots and make a line which makes the bright spot, if y'all noticed optical illusion does it for us! This is insane

[@raghavpathania016]

Best of luck for tomorrow hueheuheu

[@MJ-hq1ie]

Raghav Pathania thanks bro

[@hashirkhattak9180]

You are the wizard of physics... Damn bro wow... Such an inspiration you are... 🔥... Lots of respect Love you

[@FelisChow]

Thanks for the lecture. Got me to viusalize the phenomenon .

[@johntindell9591]

i never had an intuitive understanding until i watched this video. The impact you are having on the world is deeply profound.

[@geniusm3521]

The person, who understands best, explains best! perfect lecture about double slit experience. thank you

[@yoanch0]

Bro, you have no idea how much this video helped me understand those things

[@Telest0]

I wish I had a teacher like him...

[@mannykhan7752]

I love this guys " tough love" approach to reaching. Would love him to explain human conception.

[@shreyasmiliger1751]

I am from India and I love this Please keep continuing this...

[@Silly825]

This gonna save me

[@bettercallbhanu]

Best lecture on YDSE on YT. Thank you sir :)

[@VG__]

8:20 thankyou for this clarity

[@sarmad1645]

this is so good im speechless!

[@muhammadabdullahae2480]

Brilliant superb I could not understand it from many teachers but this let me understood

[@josephgeraci7039]

Every time I think about this concept, it blows my mind that this is how the real world works around us

[@Khgxcji]

I don't know y all teachers take same amount of effort n passion to teach. Hats off n huge respect to all those teachers around the world who explain like this , students can understand in just 10 min rather than learning in 1hr .n it's just free.respect to this teacher n channel for helping us n making a difference. Thanks👍✌🇵🇰

[@made_in_Khaos]

Relearning this after half a decade, amazing video!

[@rakinhasan3833]

I couldn’t understand this experiment... But now I can understand this.. Thanks khan Academy 🖤

[@christianpungo5210]

Now that all my college classes are virtual I can finally say (with evidence) youtube is just as good, or better than some teachers. Watching these instead of my prerecorded lectures from now on.

[@IsrarKhan-kb9hs]

Really helpful Jazakallah Sir👌

[@adthya9209]

best explanation of YDSE ever. period.

[@HM-rc7nn]

A great explanation, for which I was looking for!! Thanks for such videos:)

[@bardotons]

thank you for speaking quickly and getting to the point!!!! great video.

[@qiuk5988]

Thank god, someone is able to explain this properly since my prof is hella horrible

[@effectbest7532]

Thanks man this cleared all my doubts ....Well explained

[@savewater2840]

It's greatly explained. Thanks for this video

[@vamshikrishna323]

Iam a bit confused about this experiment..but with this vid my confusions just got rid off....thank u very much 😃 for uploading this video...

[@sreyasthejas4715]

thank u soo much for the video . one of the very best videos on interference out there.

[@rishimalhotra7331]

8:36 how did you know that i made the msitake of thinking that....😂😂. great video thanks!

[@YAC270]

I still didnt understand it? Can u elaborate?

[@unknown-ku4ri]

oh its so easy before watching this video every time i thought about this topic my mind was liking bursting Thank you so much.

[@adamdangelo7644]

You saved my life. Thanks

[@wasteyourtime4961]

God bless khan academy

[@huanganan700]

Thanks so much for perfectly visualizing the process of light diffraction. Always love Khan Academy😄

[@nicotean8376]

anyone in 2020? 🙋‍♂️🙋‍♀️

[@keme_004]

2024😂✊🏻

[@bhavanabalaraman7359]

2025

[@beyondemotionsvibe2408]

Bro, thank GOODNESS YOU EXIST!

[@pratiksaha2592]

Thank god Sal didn't taught this topic or else I don't think I could have understood so well..............Thank you so much Khan Academy for uploading this video.

[@_boss_baby_]

Awosome video, Sir can you please make a video on plane wave and circular wave with diagram ,or if possible with some simulation

[@STICKSANDSTONED]

Wouldn't the properties of the slit distort the wave? WSZ

[@sharmass3756]

super explanation I got all my doubts cleared excellent

[@somnathganapa5789]

Thank you for explaining the shape of the light waves before it enters the two slits! My textbook completely ignored how strange it looked!

[@LawGrowtopia]

My teacher’s name: Leci Things she’s good at: being useless and bragging thanks lol I’ve a test in 20 mins and I finally understand the experiment

[@beigeboi_7714]

Poor Leci :(

[@munshaatatiq1435]

Can you please add subtitles in your next videos? Thanks in advance

[@bluecloud3059]

Thank you so much. The best video for explaining Young's double slit experiment.

[@premedmelody]

This just blew my mind

[@devyanipalkar]

if you shake your head from left to right rapidly. the constructor points form a straight line to the bright spots!

[@ophiolatreia93]

I tried it and now I have a headache

[@HoussamBenhallam]

You made my day ! Thank's a lot

[@095-anamaykashyap2]

well explained ... definetly helpful for boards and jee

[@niveyoga3242]

Best explanation I've ever heard!

[@PeaceboneGotFound]

THANK YOU for explaining this so well!!!

[@atlasvv]

this gonna save me for my finals 🙏

[@roboticsresources9680]

such an excellent video..the concept is explained so clearly....best for K-12 students

[@sharmass3756]

yes

[@zahrashahabinezhad]

Absolutely fantastic videos on this topic. I finally understand this. Thank you!

[@YAC270]

Gr8 lecture, i didnt understand what 1,2,3..... wavelength is at 9:03

[@RealEverythingComputers]

Thank you so much! This video was very helpful

[@MihenHighroad]

when he says "shoooooooot" , get's me every time lmao

[@k95channel]

thanks for your helpful explanation!

[@ophiolatreia93]

I searched "young double slit" on Google and now the FBI are at my door.

[@Medusaogre]

Best explanation I've seen.

[@bhruseantv3461]

it was really helpful...thank u for such a great vedio...

[@virtualgirl7697]

Now its very easy to visualise and reason.thanks😊

[@-fish-3316]

Very clear explanation! Thank you!

[@Aliens797]

amazing explanation! thank you for the review!

[@lordepixz6364]

This video was really helpful! thank you

[@mgpvii]

I saw a video on this from Neil DeGrassi which points out the most interesting, incredible, unexplainable part of this as that if someone observed/watched the experiment the pattern would just be two slits on the opposite wall. If no one observed it, then it would be as explained in this video. It happens every time and no one can explain it. Observing changes reality.

[@Inovb]

That's explained very well thank you.

[@shreyajindal3871]

This video was really awesome !

[@GurpreetKaur-rw2ts]

Superb sir pls make more videos related to physics

[@VG__]

I request you to change your cursor so it's visible where you're pointing while explaining. Thankyou for a crisp explanation.

[@ugthankikebab]

KHAN-structive interference, I geddit

[@saisevithaa1772]

Thanks Sal! Love your vids!

[@guillaume6373]

amazing!! thank you very much

[@veerp2865]

THANK YOU SOOOOOOOO MUCHHH! THIS HELPED A LOT

[@bestmartialartsfightingsce9813]

Thank you ❤ you are life saver

[@Taqsunis]

This is absolutely amazing!!! Ty

[@paramdarshana2267]

❤❤❤Dear Sir love for u ❤❤❤Thanks

[@gustav8972]

you the goat bro

[@Dinesh-bf1ro]

7:09 but the waves seem to be interfering before they touch the display surface and not directly on the point , They are interfering at the dots mentioned and travelling to the display surface. How can we assume and calculate distances traveled so to find intensities?

[@mathewjoseph738]

this vedio is very effective......

[@Rubi747HVY]

Thanks for clarifying so well.