More on single slit interference | Light waves | Physics

More on single slit interference | Light waves | Physics | Khan Academy

Рет қаралды 170,265

10 жыл бұрын

See how there's actually constructive (rather than just destructive) interference at some points on the screen. Created by David SantoPietro.
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Пікірлер: 86

@benramprashad 7 жыл бұрын

I hate when I'm trying to learn something in school and information is withheld to make the idea simpler. It just makes me more confused! this video really helped my understanding thank you for going so in depth

@Upgradezz 3 ай бұрын

You’ll see how much is hidden as you take on higher physics

@rishabhpal9845 4 жыл бұрын

Great to know I wasn't the only one who found the high school book description of this to be, well, mumbo jumbo.

@CheyenneAnastacia Жыл бұрын

THIS IS GOD'S WORK. I've been so confused abt it, i couldn't just accept the over-simplified explanation and although this video still doesnt give the full picture, it comforts me to settle on this level of understanding urghhhh

@noellesmiley6352 4 жыл бұрын

I always teach single slit interference as being the SUM of the wave values "contained" in the slit. If the slit represents a phase difference of "2Pi" (comparing topmost ray to bottommost ray) then the arriving waves represent all possible phase shifts ... so they produce totally destructive interference. This helps to explain the two weird things about the bright spots ... ... if the topmost and bottommost rays are only "Pi" apart, they represent a "half wave" which CAN have a non-zero sum. ... for the central peak, it is uber-bright because it is the sum of ALL the rays at (near) maximum. I think this resolves the logic issues you mentioned.

@samitkhan6099 2 жыл бұрын

this is a really cool explanation ! Thank you for this one.

@Manish-bh4fj 7 жыл бұрын

Thanks u so much for uploading this...actually I lost all my hope previously to understand that why destructive and not constructive interference takes place even the phase difference was lambda though we could take it but overall super position diminishes the electric field component at that point therefore it's better to take only destructive interference..thanks for ur logic soo so so much ...I am loving it....I actually searched it for almost 2 yrs but all in vain but now having understood I am very happy ,,,,thanks for explaining that .....Love u yaar...keep it up sir...

@sailajagupta9844 4 жыл бұрын

Bhayya r u from india

@HarshRajAlwaysfree 4 жыл бұрын

All u want to say is just remember about destructive Constructive is bs

@joeljose182 3 жыл бұрын

@josebarria3233 5 жыл бұрын

"you aren't asked to find the exact locations" tomorrow bi have an exam which asks for the exact locations of those guys, thanks dude

@kiranrq9387 4 жыл бұрын

You are the best!!!!! Everytime I make sense of double/single slit experiment your voice starts speaking in my head. I only watch khan academy for your videos cuz you make perfect sense. Without your videos I would have never understood Young's slit experiments and light world never make sense. Thanks very much!!!!!!!!! Please make more videos ❣️

@Pulse_nerd72 3 жыл бұрын

So for simple understanding 1) During constructive interference Smaller waves form bigger waves, then bigger waves clash, they cancel each other out but only partially, which gives a smaller and kinda constructive peak, these kindoff bright fringe Approximately lie between the dark fringes 2)During Destructive Interference, The smaller waves directly clash with each other and destroy each other and you'll have a dark fringe.... Much simpler, I know.....

@vic4955 8 жыл бұрын

good job. this clear off my confusion

@leawangyi6769 8 жыл бұрын

thanks it has cleared things up a lot

@sarthaksharma9322 7 жыл бұрын

I got it partially, just wanted to ask that a there any formula for finding constructive points accurately?

@skiffursa3531 9 жыл бұрын

Лучшие объяснения, которые мне приходилось слышать и видеть)

@olivergriffiths3585 8 жыл бұрын

Cleared things up great

@Piguv135 6 жыл бұрын

Fantastic man! Nice one.

@skyg4803 4 жыл бұрын

Hi do you mind explaining why this does not affect the constructive wave for double slit ? Thank you !

@zinaalabdaly6848 6 жыл бұрын

My physics book says for conts. it's {w sin ø = (m + 1/2)lamda} Can we consider that the middle one goes well with this formula but it is wrong for the other conts. points? 🤔

@abhishekdhyade7500 5 жыл бұрын

PEOPLE ARE SELFISH EVEN IF THEIR DOUBTS ARE CLEARED THEY DONT THANK HIM, WHY??? YOU ARE THE BEST THANKS FOR CLEARING MY DOUBTS ❤❤

@N_0706 2 ай бұрын

Thank you so much for this explanation! I wonder why most textbooks dont explain this, its not really out of the scope of high school books

@chantony9318 3 жыл бұрын

Useful and clear!

@gaiusthegreat8234 3 жыл бұрын

I think you can also add the fact that your "reference point" (the first point you choose when you start pairing) keeps "moving" as you try to grasp the arbitary infinite points of a single slit; hence, all your reference points has unaccounted phase shifts relative to other reference points. In double slits, there is no "movement" of reference point bit there is no need since double slit is not as arbitrary as single slit.

@balkcb3725 7 жыл бұрын

i became ur fan after seeing this video :)

@D8Football 5 жыл бұрын

I LOVE THIS MAN

@nitikapruthi308 9 жыл бұрын

That was wow! Seriously!

@satyanarayansingh4882 6 жыл бұрын

Do u get some teachings?? Or it was jus wow for u

@luciano.a 7 жыл бұрын

If there is infinite many sources of wave in this slit, and it causes a interference pattern, why would it not cause a interference pattern if there was no slit at all? At what slit size does interference pattern stops ocurring?

@pankajjain9673 6 жыл бұрын

So how can we get maxima/ bright spot on screen because there will be always a opp light coming which has phase diff. of π. So how is maxima( bright spot is formed)

@georgetait386 3 жыл бұрын

Question... The problem of the points being in constructive interference but still having a different phase to all the other points, why doesnt this apply for destructive interference points?

@gopalmajumdar4140 5 жыл бұрын

please add videos on Frensel and Fraunhaufer distance

@renukadevi7203 5 жыл бұрын

Hats off .thx

@er4255 Жыл бұрын

Awesome!

@bingingawaylife8405 2 жыл бұрын

In diffraction grading we found destructive points cause the path length differences was 1.1, 2.2, 3.3 and so on. But here in one slit diffraction it should be always 1 lambda. So why would we get destructive there???

@brianneves 6 жыл бұрын

isn't the path length difference incorrect because a2+b2=c2 should be applied? am I missing something?

@MysticMD 9 жыл бұрын

Merci beaucoup

@mahdinasser4724 Жыл бұрын

Love this.

@NIHCASMIRROR 7 жыл бұрын

I am really confused now... In destructive interference if 2 wavefronts are at a phase diff of lambda/2 they cancel each other. So a crest and a trough cancel each other. But what is the physical significance of a trough in a light wave. what does it mean to have max negative amplitude at the trough. How can light amplitude be negative

@netional5154 5 жыл бұрын

I think the confusing part stems from the fact that he chooses as an example for constructive interference two waves which are four waves parts. But in that case you will be able to find a destructive wave halfway (the orange wave). If he would have chosen an example for constructive interference which are three waves apart, there would not be a destructive wave halfway.

@fritzahern1380 4 жыл бұрын

Love this

@ethann-n3007 4 жыл бұрын

Where does the constructive interference come from on the points which are beside the main bright spot.

@AnukulBasnet 7 жыл бұрын

So what about central maxima? Does same thing happen?

@chadgod2484 7 ай бұрын

Wow, thanks 😊

@fahmibassem1122 9 жыл бұрын

I'm confused

@Dismythed 2 жыл бұрын

The angle is the missing variable. It tells you both the position of the starting point and the length of the resulting wave in relation to the angle and position of the wall. It also explains how and why the light interferes and proves that light is a particle and the wave is what the particle produces. Other math is required to explain why the particle and its wave function are inseperable until something causes the particle to become superluminal so that the lightspeed-bound (because of the universal medium [c] through which the wave propagates) wave function collapses until the partical becomes luminal again. (The particle is not bound to c unless the particle is connected to its wave function.) This is also why the slit and double-slit experiments give a different effect than a round hole., along with the fact that there is no impedence to the top and bottom in the slits.

@AbdulSamiSpeeches 4 жыл бұрын

So what will be formula for constructive interference?

@kartikrao7437 3 жыл бұрын

Beautiful

@AnnuAparajita 6 жыл бұрын

wow i like it

@CJ-le3gq 8 жыл бұрын

ok so from what I understand, you're saying that it is nearly impossible to get a constructive interference because the light particles are out of phase, but what do we say about the central bright spot then ? How are the light particles able to create that on big bright spot without canceling each other out ? wouldn't their phase be different for each and wouldn't that create as well a destructive ?

@AnirbanMandal83 7 жыл бұрын

Consider 9 points (sources) instead of 8 like he draws in the middle of the slit: one in the center and 4 on each side of it. Let's marks these points as -4, -3, -2, -1, 0, 1, 2, 3, 4. Now, lights from sources 1 and -1 will travel the same distance to reach the center of the screen, so they will constructively interfere. Same will happen for the source pair +2/-2. But similar to the example he gives here, lights from sources +2 and -2 will also interfere constructively, but will be at a different phase compared to the interfered light from sources +1 and -1. Same goes for +3/-3 and +4/-4. So the net effect will be very low intensity like the surrounding peaks. However, the one from the center source does not interfere with any of the other sources surrounding it and that's why you have the large intensity at the center of the screen. Remember, that his argument for destructive interference (in a previous video) holds because there are infinite number of point sources within the slit, so it does not matter whether you assume even or odd number of sources. The same argument will not hold if the number of sources were finite.

@sherazkhan2802 7 жыл бұрын

Anirban Mandal You said waves from +1 will interfere constructively with those from -1 but it also possible for the same waves from either +1 or -1 to interfere destructively with those from +2 or -2 or from any other slit at the same point .... isn't it .... Now what can you say about that?

@shadowhunterrachel5732 6 жыл бұрын

Sheraz Khan The brightest spot in the middle is the result of precisely paired waves [ (+1 -1) (+2 -2)] to form a COMPLETELY constructive wave. Let's say you pair up +1 and -2. They will interfere, but would neither be completely constructive or destructive, hence forming the slope part of the middle wave. It is possible to be completely destructive at many points on the resultant wave, but only possible to be completely constructive at the middle pf the resultant wave where theta is 0

@qualquan 5 жыл бұрын

in single slit the MINIMA equation is identical to the MAXIMA equation for double slit i.e the INVERSE

@ashishTechieanand 8 жыл бұрын

in case of constructive interference the theta is not same as in case of destructive interference so i think both equations are correct

@XtroTheArctic 9 жыл бұрын

In the first video, I wasn't convinced that the even integers would end up destructive. I was gonna put my comment there but first I wanted to see the second video and just as I expected, you started with explaining about even integers being constructive. I think somethings wrong with the math in the first video but I'm not able to tell where because I'm not a mathematician or physician. Now I'll finish watching the second video. Maybe you already explained that calculation problem which happens in the first one.

@XtroTheArctic 9 жыл бұрын

The last part about the difference between dest. and const. points was helpful. Thank you.

@Selenium188 2 ай бұрын

Great khana academy

@hdang1997 7 жыл бұрын

so basically what has happened in the previous video and this video are: 1) we analytically found the points where constructive interference takes place. 2) we try to analytically find the points where destructive interference will take place but the points coincide with those of constructive interference. Its means that the destructive points which are found analytically are wrong. 3) so we use analytical reasoning (that the point of constructive interference cancel themselves to form the point of destructive interference) to find the points of destructive interference.

@manavshah6811 8 жыл бұрын

mind=blown

@nabayanchakma2419 2 жыл бұрын

My saviour

@auliamuhardiarifin8427 8 жыл бұрын

succesfully made me more confuse

@rohitrohan2009 7 жыл бұрын

confused*

@hwinter3347 5 жыл бұрын

Lol

@xoxo-yp1fc 4 жыл бұрын

Listen to it more carefully 🙏

@Kelvo980908 8 жыл бұрын

why does it have to be the rays that are half the slit length apart being half a wavelength out of phase?

@rohanshrothrium4155 7 жыл бұрын

cause then we can just reason out everything as symmetry.

@sherazkhan2802 7 жыл бұрын

Kelvin Fan I am thinking the same.

@hdang1997 7 жыл бұрын

the derivations were not given in my fucking nootan book. thank you so much!

@astha192 4 жыл бұрын

Why have you drawn Even no. Of sources?

@M04366597G 8 жыл бұрын

does that mean that there is no formula for constructive ?

@bruninie 7 жыл бұрын

At 1.5 speed you sound like Edward Norton

@luciano.a 7 жыл бұрын

true

@pthukral2460 7 жыл бұрын

I learned that w * sinθ = (m+1/2) λ? Is it incorrect?

@humasalam3528 6 жыл бұрын

Pratham Thukral so did I!! Dont understand!!!

@sobhanbihan6994 6 жыл бұрын

As he said, it's an approximate.

@abhishekmohanty232 6 жыл бұрын

didnt got this thing its so confusing

@qualquan 5 жыл бұрын

what a mess the Giancoli text book has a simple and clear explanation the outer bright peaks are at 3/2 lambda and 5/2 lambda etc these outer peaks are due to ESCAPE from full destructive interference, or INCOMPLETE destructive interference and not due to constructive interference as you tried to show.

@mistree0007 8 жыл бұрын

i understood evrything in last vid. this is impossible. this is HARD

@doubleja 3 жыл бұрын

For two numbers a and b to sum to zero, b must be equal to -a....so the pairing up method works. [[ "b(a)" = -a is one-to-one with "a"]]. Two numbers adding to not-zero (local maximum) can do so in many ways, and "b" need not depend on "a".

@dm7483 5 жыл бұрын

kinda sounds like lightning mcqueen

@alanamolana9767 6 жыл бұрын

kasa kr latay ho

@kidschannel6614 3 жыл бұрын

I'm so confused

@md.hasanuzzamanjihad4623 2 жыл бұрын

mumbo-jumbo🤣😂

@sanjuansteve Жыл бұрын

I’ve been saying since 2013 that it seems extremely obvious that all electrons and photons are in orbit with a dark matter particle. Based on Fermilab and other recent findings, I now think electrons are made of an electron neutrino entangled in orbit with a dark matter muon neutrino, explaining their erratic orbits around nuclei and explaining superposition and uncertainty. I think photons are a pair of electrons entangled in orbit together in apparent an axial or helical polarizable wave-like movement depending on the direction of their rotation as they travel. This explains the double slit experiment for example and the speed of the rotation explains electromagnetic wavelengths (and visible colors, etc). What do you think of this Mudfossil University video?: ‘’Light Duality Solved and Seen’’, Sep 29, 2022