Diffraction: Why Does It Happen? (Physics Explained for Beginners)
ฝัง
- เผยแพร่เมื่อ 5 ก.พ. 2025
- Why do waves bend around objects or when passing through slits? Why does diffraction occur?
Timestamps:
00:00 - Intro
01:13 - What is Diffraction?
02:56 - Huygens' Wavelets Model for the Motion of Waves
04:29 - Wave Interference
07:37 - How Huygens' Model Works (and Explains Diffraction!)
11:24 - Problems with Huygens' Model
12:04 - How Fresnel Modified Huygens' Model (Huygens-Fresnel Principle)
14:36 - Announcement!
Hey guys, I'm back with another video, one which has been requested by a few of you! In this video I discuss a way in which you can VISUALISE how diffraction occurs. Hopefully after watching this video, you'll be able to understand why waves behave in such a strange way when passing through slits or when passing around objects, rather than just accepting that they do.
Of course, I need to make a disclaimer that the scientific models I discuss in this video (Huygens' Wavelets and the Huygens-Fresnel Principle) aren't necessarily how waves actually behave in real life - they're just really good mathematical models that accurately predict how waves behave in real life. But then, that's true of the majority of physics anyway.
Christiaan Huygens came up with a fairly simple but very clever way of understanding wave behaviour by breaking up waves into lots of small chunks that all behave in a very predictable way - by emitting lots of "secondary" waves. His model helped scientists to understand and visualise that waves must indeed bend in a very specific way when passing through a slit, or around an object. The idea that each point along a wave acts as a source of secondary waves, along with the idea that each of these secondary waves interferes with each other secondary wave it interacts with, accounted for a large chunk of observed wave behaviour.
For this reason, I wanted to show you Huygens' model, as well as talk about wave interference. For those of you who don't know about interference, and aren't happy with the pretty speedy and simplistic explanation I gave in this video, I highly suggest you check out the wikipedia page on interference. It's an idea often taught at high school (or college) level physics and it's mega interesting.
Huygens' model, genius though it was, had a few flaws. When we say flaws, what we really mean is that the model's predictions did not perfectly match what we observe in real life. So Jean-Augustin Fresnel came along and modified the model to make sure its predictions did match observed phenomena. Fresnel added an "obliquity factor" to the secondary waves emitted by each point, a sort of attenuation or "strength" factor depending on which direction these secondary waves were travelling in, as well as modifying the phases of the waves moving in each direction from a point source. These modifications to Huygens' original model naturally meant that Fresnel had created a new model entirely. This model is known as the Huygens-Fresnel Principle.
With all of that being said, I hope you enjoyed this video. Please leave a thumbs up and subscribe to this channel if you enjoy physics content like this, as well as to my new second channel Parth G's Shenanigans (link: / @_parthmusic ) if you want to hear some of my music. Also follow me on Instagram @parthvlogs. I'll see you soon!
I love it when you just find a random video of someone that understands something enough to be able to simplify it
*Dude, I just read the Huygens' Principle in my textbook like three times... I just grasped it now with your explanation. Thanks a bunch.*
Same its really difficult to understand it through textbook
Great channel you have a talent for explaining :)
so true
You too! I love your channel
Your channel is awesome too.
SIMP
Wow reply from another great channel..!!
Wow man, you have got some serious skills of explaining, This is what everyone wants from a teacher that is explaining everything from scratch, not expecting from the student to have any knowledge, please never discontinue this
My goodness thank you so much for making this. Trying to explain Huygen's construction is one of the most painful things I've ever had to teach.
Right....most hard thing for BANGLADESHI students ever
@@alakh2472 are Bangladeshi student's brains fried or something? why would Huygen's wave principle be the one that's so hard for them to understand
This man is obnoxiously underrated. He explained diffraction in the most understandable way. Could never have understood this without ya. Thanks man ✊
0:07 "The outbreak shall not be named"
0:16 "In this video ill take.... ***** outbreak"
Well thats only 9 seconds..
It sounds Voldemortish
@@kayrstar8965 exactly!
Was about to make this comment…😂
currently IAM doing bsc in physics from TH-cam university. thank you
same its fun knowing all this when u in highschool XD
@@shri2820 😁👍
@@shri2820 It's more fun when you know it in middle school.
@@chinmaykrishna6485 too bad i totally hated physics in middle school
@@theoenomelphilosopher8687 Actually teachers make physics boring.
Ok, I've watched this video several times since it came out, I think I finally got it! Nice way to put this whole diffraction concept, thanks!
Yes me too and still, yet if I get what is wonderfully said in this Video it will not answer your question in different scenarios like if you imagine with different wave lengths the Arc of diffraction is different : Bigger wavelengths tend to have a complete arc of diffraction while smaller wavelengths get a very small arc.
In this video it explains it : th-cam.com/video/BH0NfVUTWG4/w-d-xo.html
FInal someone that explains the theory instead of just saying this is how it should be.MUCH APPRECIATION
I've been looking everywhere all night for an explanation of diffraction through a slit and glad I didn't give up! So many videos state that diffraction just exists and don't explain why and it drove me CRAZY. Thank you so much
10:36 everything just clicked for me. I love beautiful “aha” moments like this. Thank you!
As a person who always need to visualize the ideas in order to being able to work with them I am really grateful for your explanation
This was awesome, I can't imagine how much work must go into this.
Thank you so much! I’ve just started a degree in diagnostic radiography (after a long time out of education) and have little physics background. This has been a really helpful resource to cement my learning. You have a great clear way of explaining, making this less complicated. Thanks again!😃
Exceptional explanation 👏👏
This is the best explanation of diffraction I have ever seen.Thanks
Biggest Physics brain of TH-cam. Thank you for existing
You made the concept so easy....i can't believe that this 15 minutes video made me understand the whole topic which I was trying from last 5 hours..
Thank you its really gonna help me in my seminar.
The best explanation!
Your way of explaining is simply magic ✨
👍
i am not even a high school student. I recently passed 9th grade but still was able to understand.
P.S : I am good but not an excellent student in this subject.
THANKS A BUNCHHHHH
A talented man gliding over complex subjects - enjoyable.
It's was extremely amazing I never get while I was reading it many times but you made so much for me to understand itt❤️
TH-camrs like you save me from the boring teacher curse. Thank you for keeping my passion for physics alive :D
This is exactly what I was looking for, LITERALLY. This world needs more explanations like this.
Generally, what we learn in school only covers how things are, but not WHY they are the way they are. I know that it's not always easy to understand the Whys and sometimes it's best to be understood once we have command over the basic concepts, which we'll eventually build, but I still can't help but explore. Videos like this show that it's still possible to have a basic conceptual understanding of these things.
Most explanations online just throw a bunch of complicated words to sound smart, but don't have much substance. This video was AMAZING though. It PERFECTLY explained everything coherently and the visuals were great! Now, THIS is how explanations are supposed to be.
I'm going to go binge watch all your videos now😭
Also random, but I want to be doing the same thing in the future. I want to explain all these fascinating concepts from scratch in a way that makes people feel "Aha! so that's how it works". That feeling of understanding something makes me tear up (tears of joy ofc)
Your simplistic way of describing complex things makes me dig deep into physics even if I don't belong to the field!
Can you explain (derive) Einstein's field equations as well?
shut up
@@overlord3481 Calm down kiddo, Calm down
@@ramsesll2841 fight me. then i'll show you which field you truly belong in...
@@overlord3481 lmao LOL
@@overlord3481" fight me"
We're not that advanced yet
you should get an award for this explanation. Thanks!
This was one the best educational videos I have ever seen! Thank you
So glad I found this channel ❤️❤️❤️.
Soon I'm taking the Optics exam from my physics degree and it has been really clarifying.
Thank you very much Parth. Subscribed ;)
As soon as i saw the title, i subscribed. I love first principle questioning
Amazing video. I can't get better than this. Explained every concepts simply. Support from a Nepali
The best description I have ever seen. Simply great.👍
The most clear explaination about this topic. Great work and thank you!
Never got such simple explanation from anyone
Thanks
This video is just so amazinggggg!!! I have fallen in love with waves...tysm!
Thank god i found your video.
U just taught wave optics in 15 min.
Thank you and may god bless you.
wow, what a nice channel! You explained everything in such a clean, clear and to-the-point way! Thumb up and subscribed! Would you explain polarization?
One of the best of all your uploads
Wow, thank you so much. I am just learning about the huygens-frenell principle so this was very usefull!
The best description I saw, thanks my friend
Finally you helped me in understanding ...Huygens principles and why light bends at corners... thanks very much
It was awesome 👍 physics can be described without maths, u've just proved it.
A wonderful and clear explanation! Thank you!
just amazing👌best video on diffraction
thanks for the simple yet detailed explanation of diffraction.. ❤❤❤
Great video, I wasn't aware of this explanation for the explanation of diffraction. Food for thought 😁
Scattering theory refers "secondary wave" as "secondary source", and it is possible to be higher order, third, fourth and so on. Very nice explanation, you are genius.
Bro you got some serious talent 🙏🙏🙏 Too good explanation
You are the definition of Physics Teacher! Thank you so much!
U da best. The way u teach is exceptional. Not all heros wear cap.
You should be my physics teacher. You'r the definition of amazing at explaining things.
CLEAR CUT EXPLANATION SIR! THANKS A LOT.
You explained it very well.Taught every corner of it very clearly.....I subscribed you. Thanks a lot..
What an explanation Parth!
LOVED the explanation!
Congratulation Parth for 100k subscribers ! Big day for you and for us who constantly look forward for your videos 😊
Hey Parth! I really love the way you make things seem simple! Would love to see your perspectives on reciprocal space soon! Take care :)
It's amazing the way you have made these things so simple!
Thank you !
Hey Parth! Amazing video, as always :) I have a fundamental question - Hyugen makes the basic assumption that each point on the peak is a secondary wave source. Considering the fact that the rest of the principle relies on this, on what basis did he make this assumption?
What is its validity?
Because intuition + it is consistent geometrically. Divide a circle's circumference into infinite points and draw smaller circles with each of those points as new centers. Now, draw tangents to each of those small circles, what you will get is bigger circle that is concentric and larger to the one we started with. This is nothing but a new way of drawing concentric circles and waves propagate in concentric circles in a medium (regular observation). So, in this way treating each point on a wave front (circle) as secondary sources of new wavelets is consistent mathematically. In simple terms, a good thing to bet on.
I had the same thought. I think it begs the question. What really is the wave?
@@PassingThrough1972disturbance propagating in transverse direction or in longitudinal direction.
Hello Parth G, I have a burning question concerning diffraction: After passing an obstacle, a wave also propagates into the shadow behind that obstacle. Imagine the obstacle as a wall. What determines the angle between the wall and the outermost waves? Why does it seem to be smaller for light but bigger for sound (you can not really look around corners, that you clearly hear around)? Now imagine another wall closing in creating a slit of decreasing width. As far as I have understood (which is not very far) a smaller slit would decrease the angle between the wall and the outermost wavefront, until the slit is as wide as the wavelength and the wave emerging from the slit can be treated as a point source of that wave. Does that mean with a very small slit you can look around corners? If this is true, why does that angle change during the decrease of slit wideness? How does the wave, formerly propagating around a corner "know" that the other wall is closing in? Thank you for this great informational video!
Greetings Zozo
This was so concise!
Thank you I am at high school and this magical phenomenon was buggin at me for months now!
p.s. I watched the whole video, and now am convinced whole physics is a sham. Hooray maths, damn you natural so called laws. Hopefully Wolframalpha's so called fundamental theory don't turn out to be a sham too, so we can have some definitive stuff
I am new to this channel and love this kind of videos hope you will be making more such videos
I am in grade 12 so this kind of videos really helps enhance my understanding of physics.
Thanks a lot😁😁
Very good explanation and especially the visualization)
You made it easy to understand, thanks!
Thanks, makes it somewhat clearer.
Awesome bro, great way to spread your knowledge, I have understood now
Wow, thank you so much. I don't learn well with textbooks, and this really helped me understand.
Fantastic stuff Parth.
this man is a god send
After seeing your video now I am able to understand diffraction after 7 years
Thank you for this explanation. I was wondering though, why the wave bends but then it seems as if it starts to be straight again
Glad youtube helped me finding you.
Hearts.
Great explanation! Well done!
Very nice explanation 👍👍
Oh my god you are so talented and genius!
This was extremely well done, and very comprehensible. Thank you so much!
I love the setup behind you!
dude your channel is gonna blow up
you are such a talented scientist, and should be much more subscribers。。
very nice explanation. thanks for the video. Great work, keep going!
Your explanations are great.
Wow what a fantastic explanation!
Superb video Sir. Thank you for this explanation ❤
Thanks sir
Now I understand it better ❤
such a good explanation! so helpful:)
I liked,jus because you have timestamps
And because the video was super helpful,but the moment I saw timestamps I liked
Thanks for the great visualisation
Very well explained and seems v logical 👍
Very good and clear explanation. Thank you I am enlightening 😊
Amazingly explained 🙌🏻🙌🏻 thanks a lot
Great Channel Buddy💜
Awesome video, wonderful explanation
You made an awesome explanation. Loved it
Amazing video as always. I understood most of it but what confused me was why in the primary waves (in the diagram you drew they are the lines) do not have bend towards their ends as well. Moreover, there are other points of constructive interference (of the secondary waves), which also form a line- what do they represent?
Also, the first wave after the slit is not round but flat with round borders... I wonder if we get that same shape in reality too ?
Well, the primary plane waves actually stretch infinitely on either sides.. only the part that hits near the slit is shown in the diagram.
@@arvindupadhye6172
But do we obtain that shape in reality just near the slit ? Or is too hard to measure precisely ?
Thanx for the time stamps, really useful
Thank-you so much.You explained is help me understand the wave much more than be for. 😄
Awesome explanation Sir.Keep up your great work.Thank you.