Demonstrating diffraction using laser light - for teachers

In this short video, from the Institute of Physics and the National STEM Learning Centre and Network (www.stem.org.uk/), Michael de Podesta explains how a laser can be used to show the diffraction and interference of light. Using a laser pen in the classroom, the wave nature of light is demonstrated as a thin wire is used to generate an easily-seen interference pattern. Two versions of the video are available. This one is suitable for teachers and fully explains the demonstration and how the interference pattern is produced. The second is aimed at students and could be used in place of the demonstration.

[@cynagye2096]

Looking at how he is explaining makes me love physics

[@mahirhasan9212]

This is awesome 💚

[@hugohidalgoherencia5241]

What happens if you do it with 2 wires ?

[@delete7316]

I would guess that you'd have more pronounced dots with larger spaces between them due to more sources of interference. It would only be very slight and not easily visible to be different. If you want to see what would happen if there were loads of wires, look up diffraction gratings.

[@Mufti199]

Such a brilliant experiment! I'm definitely integrating in this in my class

[@lorentz1617]

Definite integration 🙄

[@varshakhadilkar1646]

Who all are jee aspirants here

[@LuvinaMacondo]

Thanks! That's what I was looking for.

[@daydreams9113]

"For teachers" *me watching for fun* ;-;

[@hoofheartedicemelted296]

The difference between college and university level learning is in university level you are "reading" whatever subject matter, so in effect you are teaching yourself. Where as in college the teacher is teaching you, relaying the information and laying it all out for you and hopefully simplifying the subject matter as much as possible. I asked my brother how is it you have taught yourself to use cubase which at the time, many years ago, there was no tutorials for it. He said "if you have a passion for something, you will have eagerness to learn and it will be absorbed much easier". Well I have a passion for optics, but I'm still baffled and this teacher has made perfect sense. I'm struggling with a lot of the subject matter so diverse is it, but what he just explained was easy to absorb and made sense. Sometimes you just need the best teacher. The institute is blessed to have him. I am currently reading a book I bought called "Optics The Science of Light". It also has the IOP mark on it, and it's a fascinating read. But God what I'd give for someone to explain it in videos like the video above. I wish that this subject was available when I was at school. I think my life would have turned out quite differently indeed. Thank you good teacher for passing on this knowledge of physics and the science of light.

[@nikhilgarg2929]

2:32 u will be able to see difraction

[@jerichobauner5914]

THANK YOU! FOR THIS! :))

[@nikhilgarg2929]

@@jerichobauner5914wlc

[@jerichobauner5914]

@@nikhilgarg2929 E

[@bethevers6391]

Thank you so much for a lovely demonstration to use in class.

[@fatimamir2006]

Thank you Sir It was so interesting and easy to understand with more focus

[@maxheadrom3088]

I did it using two razors to form a slit. Excellent video!

[@nikorahmad]

Im a physics teacher from Indonesia and i love it.. 👍

[@SuperBhavanishankar]

Hello sir

[@nikorahmad]

@@SuperBhavanishankar hello..

[@Rohitsingh-dg1oj]

Sir what will happen if we project 2 laser together Will it show interference

[@maxheadrom3088]

Well, there's interference but it's likely not visible because I don't think you can guarantee that every photon will be produced with a 90 degree phase difference. When the laser goes through the wire it forms something like circular waves on each side of the wire - with the same phase - and it's the interference between these two "sources" that produce the pattern. Huygens, when he proposed the wave nature of light, designed an experiment using a thin hole that should produce circular pattern of interference. A video showing waves in water: kzbin.info/www/bejne/b5jYmnlnabOKprs A simulation of the double slit experiment in water (each side of the wire behaves like on slit): kzbin.info/www/bejne/ZpTdpXygZtJqm5Y Hole electron diffraction from an Australian school: kzbin.info/www/bejne/g5qscqGufr9-h9E

[@pham9479]

you can search Michelson interferometer

[@blackbuildinc]

Light. Light? Electromagnetic Radiation? Electromagnetic Waves? Light? There is so much more too light than science. If we are light, and everything is light why is it here and where did it come from? Why can it can have a momentum but not have a mass? You need a mass and a direction to create momentum...

[@gregoralexander1856]

Although it may be seemingly deceiving that an object needs to have mass to hold momentum, this isn’t the case at relativistic velocities as photons of light have energy in the electromagnetic form and since E=mc^2, energy means mass and therefore momentum

[@apusingh1967]

is diffraction a proof of uncertainty principle?

[@harshitmishra3622]

Ha bhai DPS Gr.noida ka kon kon aya hai yaha pe 😂😂😂😂😂

[@sharad7340]

Thanks my physics teacher used it for teaching

[@ARCSTREAMS]

ok i understand that constructive interference creates a double amplitude thus brighter light is that correct? and destructive creates no light as the throughs cancel but what about when there are different semi constructive or semi destructive phases 1/4, 1/2 etc where do these appear? are they the bands of light that are less bright and why are these happening further to the sides away from the middle? the same constructive patterns happen away from centre as well but why are those less bright though? also if we have a collimated beam of white light will there still be refraction and interference only it wont be creating fringes because there is a jungle of different light frequencies ? if so how come they still cast a near perfect shadow of whatever you put in front of this beam for quite a long distance before it blurs of fades away?

[@mayankpunai7093]

I am a student of FE4 batch any one here from GCI

[@exoplanet11]

Thanks. A much better video than the old one MIT has up on the topic. Modern and conceptual. I am using this video for my physics students at San Francisco State Univ.

[@bhigurammahato7228]

Im looking for this Explaination

[@pinacolarusso]

This is a brilliant video. Short, rigorous yet fun!

[@mugdhomugdho3013]

The producer is a BENGALI

[@parithimathi]

Excellent demo. Thanks. I'll use it in my class

[@lovenaturechannel8080]

i dont think so where is slit??? single slit or double where is

[@jeenasubedi22]

Is this possible in normal room? Or need a dark room?

[@archanasengar2854]

He looks like Christopher Nolan

[@NikitaNair]

Amazing explanation!!

[@applesweet55]

His calmness eases my physics anxiety

[@odal6770]

@Michael de Podesta did you ever spray the space between the laser and the screen after you had placed the wire? Did you see that light rays were reaching out to the screen, the way the central beam did? I think they do not and that is quite a puzzle. How do the reflections get on the screen if there was no impact other than that of the central beam? I would really appreciate it if you would react to this comment. Even if it is to show that I am completely wrong. If I could I would build the same setup as yours, but I am not very handy I'm afraid.

[@razz6475]

Woww.. that would be interesting to explore. Thanks.

[@odal6770]

@@razz6475 Please let me know what you find out.

[@odal6770]

@@razz6475 kzbin.info/www/bejne/rJDYc5R4qsale68 The beam certainly is not as wide as the pattern on the screen, is it?

[@razz6475]

@@odal6770 yeah it isn't. The lady tried to explain using the arrows, which almost seems like divergence of electric field from a point source. Anyway really appreciate the comment.

[@kalitgautam]

The most beautiful Diffraction video I have seen till date !!!

[@Spoder_07]

His voice is so soothing, it made me forget I'm seeing this for homework

[@physarif]

Great explanation.

[@bravedelchannel5067]

Thank you for explaining. You saved my day.hahahha

[@padmalathaumesh5590]

Very beautifully explained, experiment is demonstrated so well, tku sir

[@Dashing_dev_18]

Physics works ❤

[@syedhasnainahmed9097]

Excellent 👌 Without double slit or diffraction grating

[@atangreid4270]

Science class has me like 😴

[@SuperBhavanishankar]

For me history class is like 😴

[@lepidoptera9337]

You want to expose the wave nature of light? Look at an oil film on water or press two glass plates against each other (microscope slides will do fine). No laser necessary.

[@n4v33nkum4r7]

This is basically Charlie Puth teaching me physics😳😳

[@navneetkr.1192]

Thnx, it was more helpful than one may think.😁

[@theVO1D31]

When you are truly in love with physics, you speak like this ⬆

[@mukeshwathore944]

Amazing explaination 🔥

[@arvind7820]

Great Explanation sir. 🙏 🙏. The most aprecite thing is the quality of the images.

[@anujmalik7887]

I am studying this in my class 12 [India] . Sometimes i feel like i am a scientist xd .

[@jamesanonymous2343]

IF YOU'RE INTERESTED IN GETTING TO KNOW HEISENBERG AND HIS THEORY, THIS GUY WILL GET YOU STARTED IN THE RIGHT PLACE,,,AND THE RIGHT DIRECTION ,,,,,,,,,,,,,,,GOOD LUCK ! THANKS,,,,INSTITUTE !

[@genmckenna3718]

brilliant ..beautifully explain..thank you

[@rakesharora7714]

Thanks a lot

[@ecwg8512]

Dr. Chan rise up

[@odal6770]

@Michael Podesta I wonder what one would see if one replaced the screen with a mirror? The circular spot of the laser and the wire? Or the same pattern as with the screen?

[@sheetalarya9669]

Amazing Sir 🔥 Love and Respect from India 😊

[@-MikaelaWuisan]

Thank you Sir. It really helped me understand:) Have a good day..

[@suchismitabehera5783]

Thank you so much sir.a great respect to you sir.explain the experiment nicely.

[@jamesanonymous2343]

CURIOS TO KNOW,,,IF LIGHT IS A WAVE, AS APPOSED TO A PARTICLE, WHAT ARE IT'S (WAVE), CONSTITUENT PARTS ?

[@ag887s]

Thank you for the explanation ❤

[@yerragudisivamohanredy8160]

Super 😙

[@kurshidulalamlaskar8744]

Thanks to you for clearing my doubts regarding this topics

[@gijoraj623]

Wonderful wonderful explanation

[@ritazaghar8304]

est ce que vous pouvez faire la traduction en francais

[@dadagdadig5344]

Thankyou sir , I was just looking for this explanation.

[@odal6770]

What would happen if you brought the wire very close to the screen? Would we then see a shadow of the wire?

[@jamilurrahman6360]

Wonderful 👍🏻👍🏻👍🏻👍🏻👍🏻👍🏻👍🏻👍🏻

[@DrAnkitJangid]

Ok

[@michelecutini1503]

Excellent work, well done!!

[@rasheduddin8811]

loved this video presentation. awesome!

[@physicslelo7614]

Amazing style to teach and demonstrate.. loved it

[@fititocom]

i like to use two tangled hairs to do the same

[@cslloyd1]

Feynman says light is not a wave at all, only a particle. He would have used QED and Feynman diagrams to explain this and would say QED is the most precise/correct theory in the history of science. Why do we keep talking about waves?

[@lepidoptera9337]

Because what Feynman means when he talks about particles are actually quanta. Quanta only exist wherever there is an irreversible energy transfer between an electromagnetic field and an external system. The notion of a quantum within the em field itself is unworkable (it leads to the well known problems with physical realism). It is also complete unnecessary. You do have to understand, though, that these details do not matter to Feynman because the formalisms of QED and QFT in general are taking care of this automatically (and so does the Copenhagen interpretation of non-relativistic quantum mechanics). As a theorist who is mostly concerned with predicting high energy physics phenomena he can allow himself to gloss over these details and it does not hurt his ability to make solid physical predictions. If you are more interested in the structure of quantum mechanics than actual physics (like the standard model), then you have to develop a somewhat refined sense for how you want to talk about these things. When you do, however, you will quickly realize that this refinement is mostly cosmetic. It doesn't allow us to make any physical predictions that do not also pop out of Feynman's crude way of talking about these things in the particle language of the high energy physicist. It's pretty much all just icing on the physics cake, if you like.

[@saritapal-dk4lg]

Simply explained👌👌👌

[@sandhya41a5]

Thank you so much sir ❣

[@iamvanshchauhan]

Brilliant experiment

[@jaansayyed8632]

You really deserve more likes 👏👏

[@cynagye2096]

Normally I don't lol

[@mechanicsforigcse524]

very very nice

[@fikirbirhanu5983]

thank a lot

[@shadowmonarch8304]

This is amazing!

[@robertwilsoniii2048]

This is awesome. It seems super obvious after spraying the lazer beam with water that it is a wave. You can see the oscillating photon partials moving towards the paper. I guess hitting hair causes the photons to scatter and bounce, I assume the same damn thing happens to water particles if you interfere with water waves.

[@joeplana]

The pattern would disappear if you blocked one side of the divider.. would that be right? And equally if we marked the photons in some way to determine which side they travelled. It is essentially the same as a double slit experiment... or is there a significant difference?

[@neerajpathak1600]

India🇮🇳 ❤

[@mdshimul1504]

Thank you sir

[@mdshimul1504]

🇧🇩