Physics 60 Optics: Double Slit Interference (1 of 25) Path Length Differences 1

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In this video I will explain Young's double slit and how path length difference yields the dark-bright-dark-bright interference pattern.

[@rogeliotorres2581]

Thank you for giving us such amazing lessons for free, without this I would have suffered a lot more in physics.

[@MichelvanBiezen]

We are glad the videos are helping. Thanks for sharing.

[@Priscilla.09]

Thank you for being such a great teacher! More useful than my college professor's lectures.

[@erbyghazar7372]

Like always, amazing. I dont know why we people finde the best teachers just in KZbin chanels :) . You explain clean and fast. Thank you.

[@MichelvanBiezen]

Thank you. Glad the videos are helping.

[@mohamedsherif2191]

You are wonderful, really you are the best in many branches of physics comparing to others

[@MichelvanBiezen]

Thank you for your kind words

[@prince-mercyhabtemariam3412]

This guy is literally pulling me over to the light

[@MichelvanBiezen]

Glad you found our videos helpful! 🙂

[@valeriereid2337]

Physics at its best! Many thanks, I appreciate these lectures.

[@MichelvanBiezen]

Thank you.

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[@quon535]

Honestly without you, I would’ve have gotten through physics! No one matches your explanations man I’m telling you

[@MichelvanBiezen]

Great 👍

[@hythe4936]

So because for very small values of x, Tan x and SIn x are indifferent we can basically say that they are equal

[@MichelvanBiezen]

That is correct.

[@shahananizar6991]

Thank you so much for your wonderful lecture, it was very helpful!

[@MichelvanBiezen]

Thank you for sharing, glad it was helpful.

[@russellkane9439]

Great lesson as usual

[@MichelvanBiezen]

Thanks! 😃

[@Ray-ye8gz]

How did you know that the thetas are equal? I saw 3 theta in this video but I didn't understand why the thetas are considered equal... especially, the two thetas at the upper one...

[@MichelvanBiezen]

Because of the rules of similar triangles. The two beams going from the 2 slits to the screen are essentially parallel (they don't look parallel on this drawing because the distance between the 2 slits are greatly exaggerated in order to show the details).

[@Ray-ye8gz]

I don't really know how to thank you... As I was suffering a lot with this misconception Thanks a lot!

[@debarghyachattopadhyay2614]

Really ?

[@FA-cr6qf]

awesome videos, very helpful.

[@SaRa-vq7mk]

thank you

[@MichelvanBiezen]

You're welcome

[@LiveLetsLife]

What occurs when the waves are neither perfectly in phase nor a half cycle out of phase at a point? Do they still constructively/destructively interfere but to a lesser degree?

[@MichelvanBiezen]

That is correct. If you watch the remainder of the videos on this topic we cover the cases in between as well. (for both interference and diffraction).

[@roselynnwood4657]

They would make a bright spot but of much lesser intensity because some of the wavelength is getting cancelled when they are a little out of phase but some of it is still in phase and that would not be cancelled so theres a little light

[@ranitbanerjee956]

Sir I have a doubt.What is the thickness of one bright fringe?(I am not asking fringe width) Sir please answer.

[@MichelvanBiezen]

The word "thickness" is mostly associated with path length traveling through the medium or object. That is not used or needed with a double slit interference pattern. If you have a specific example in mind we may be able to answer this question better.

[@MohamedGamal-rv3cm]

Dear , I'm one of your fans, honestly , I didn't this video, I think you have time to create another one with showing the relationship in theta , coz I'm confused. deriving is not clear, thank you sir

[@MichelvanBiezen]

This is explained in the playlist: PHYSICS 61 DIFFRACTION OF LIGHT

[@TheMacC117]

Why do teachers insist on telling us that the rays are parallel, and then talk about them coming together? The literal definition of parallel lines is that they will never touch. Ever.

[@nyasajain837]

Reasonable Gump Well...actually there are parallel rays its just that there is a coverging lens (convex lens ) in the setup too ...to coverge the light ...the lens is not usually shown to avoid complexity ...hope it helps u

[@KnightofGreeness]

The rays are parallel as they approach the slits. When they go through the slits, the rays diffract, becoming Huygens sources and going in all different directions, making them able to interfere with eachother. The parallel-ity ends after they pass through the slits.

[@georgeabreu6392]

In short, that’s a physics thing. It still works for modeling reality.

[@deepakchandravanshi6274]

suppose if we get 6 maximas including central one,then what about the intensities of all maximas.are they have different intensity or same.

[@MichelvanBiezen]

They tend to drop off. There are videos in the playlist that describe that in more detail.

[@andrewskyworker]

y length should be a litte longer , if we take your y length then it would not be 90 degree against L ,? y should go down a liitte bit more to descirbe tan (theta)?

[@MichelvanBiezen]

Remember that y is very small compared to the distance to the screen. (L >> y) We draw it this way so you can see what is going on (not to scale)

[@nahidfarzin6833]

It's helpful

[@Peter_1986]

I once tried deriving an equation for the actual geometry in an interference pattern, and that equation was horrible. I think it became a transcendental equation or something like that.

[@markberardi109]

Hi, just comparing to destructive interference to mechanical waves: in a sound waves, when high p meets low p there will be destructive interference; in water waves, when a peak meets a trough there will be destructive interference; with light waves through a slit ... the light waves are out of phase and cancel with each other? This seems odd, because normally if you have 2 light sources they seem to add in intensity. Is this always the case or is possible to get light sources to have destructive interference?

[@MichelvanBiezen]

When that was first discovered it was revolutionary. It is indeed correct that light experiences destructive and constructive interference. In order to see it you have to use monochromatic light, thin slits with a small separation distance, etc.

[@spaceshipastro]

thanks alot, i wish for you a beautiful life

[@MichelvanBiezen]

Thank you. 🙂

[@maghroorali733]

is it possible for sustainable images to disappear in youngs double slit experiment??if yes den how

[@MichelvanBiezen]

What do you mean by a "sustainable" image?

[@maghroorali733]

Michel van Biezen bright images

[@MichelvanBiezen]

If you shine a monochromatic (single wavelength) light through a double slit, you will see a series of bright spots and dark spots on a screen in front of the double slit.

[@maghroorali733]

Michel van Biezen the fringes can disappear if we increase or decrease the slit distance??

[@MichelvanBiezen]

The separation distance between the fringes will increase when you decrease the distance between the slits. Watch the other videos in the playlist on the topic for more understanding

[@jacobvandijk6525]

Why should two constructively interfering waves always give a central maximum? By moving the screen you could make that a central minimum, isn't it???

[@MichelvanBiezen]

The location of the fringes is a function of angle, although the angle will change as you move the screen closer or farther away. The central max should be directly perpendicular to the slits on the screen, regardless of the distance to the screen. There is no difference in path length for the central max, therefore the distance to the central max doesn't matter.

[@jacobvandijk6525]

Thanks, Michel. I'm trying to understand what you wrote ;-)

[@unbelievable1560]

Can someone help me please. In some notebooks for destructive interference it says that delta x=(2m-1)*lambda/2 and in other there is plus sign after m. Help!

[@MichelvanBiezen]

It is just a different mathematical way to say the same thing. if m is an integer then 2m - 1 = 1 (m=1) 2m - 1 = 3 (m = 2) 2m - 1 = 5 (m = 3) (and then it is multiplied by lambda / 2) or m + 1/2 (and then it is multiplied by lambda) the result is you end up with the exact same thing

[@unbelievable1560]

@@MichelvanBiezen Thank you man, i can't tell you how much you are an inspiration.

[@_John_Sean_Walker]

½λ = 333nm 1½λ = 999nm d < ½mm L = 2m L/d = 4000 Where is the first dark spot?

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Creo que encontré ORo x.X

[@MichelvanBiezen]

? 🙂

[@cisomophiri6877]

Thank you

[@Electric1999_9_]

thank you

[@MichelvanBiezen]

You're welcome