Light Is Waves: Crash Course Physics #39

The way light behaves can seem very counterintuitive, and many physicists would agree with that, but once you figure out light waves it all starts to make more sense! In this episode of Crash Course Physics, Shini shows us how we know that light exists as a wave and why that's really cool!
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[@crashcourse]

We made quiz questions to help you review the content in this episode! Find them on the free Crash Course App! Download it here for Apple Devices: apple.co/3d4eyZo Download it here for Android Devices: bit.ly/3TW06aP

[@izzlez]

"studying waves has its ups and downs" 😂 I love this

[@Nihilnovus]

When I greet light, light waves back...

[@booboo8675]

EEEEEEEEEEEEEEEEEEEEEEEEEEEEEEY!

[@ZeeGhost713]

tragoedia veritas lol

[@Godcatforlife]

*claps*

[@darknightofthesoul8980]

A photon walks into a hotel lobby. They ask it if it wants help with its bag and it replies "no thanks I'm traveling light" 😁

[@flaming_mountain_spark2927]

funnnyy

[@ZeeGhost713]

Lol

[@timkohut1305]

Lol fungal

[@kennygerberich4985]

**gives four wedgies**

[@ragepheonix3952]

This is driving me nuts!

[@fossilfighters101]

Oh man Shini, I've learned this three times over two years, and this is the first time this has made any kind of sense to me. Thank you.

[@Master_Therion]

Is light a particle or a wave? Or is it just *particularly wavy?* ;) joke, not a real question.

[@seggplant9455]

Master Therion both

[@jaydupree418]

Master Therion Light is a wave made of photons.

[@j.miguel6193]

well check the "double slit experiment" before you post videos... light can behave both ways... in another words, god exist

[@aajjeee]

are you serious when you say the wave particle duality implies god exist?

[@j.miguel6193]

+Barnesrino Kripperino yep not only me but einstein thinks the same... 'observer' the 'watcher'

[@romelmorrison7581]

Even though it is above my grade level it still helps so when I go back to school i will be ahead of the class in some areas

[@MI-lo2hj]

Hey ur voice travels at the speed of light😂😂😂😂😂

[@preciousnthabeleng3250]

True😂

[@vonneely1977]

I keep waiting for her to take a breath but it never happens. o.O O.o O.O I, for one, welcome our new Smart-Bot overlords.

[@porygon-z4503]

Von Neely 4:51

[@Doc_Loc]

you fool we must fight agains the Overlords to become the new overlords

[@shaziashah8645]

Von Neely she's a skinny gurl

[@HomoSeal]

Breathing is for people with no editors.

[@geetika6540]

5:06. Well done

[@sarinaadeline8811]

These videos are amazing, and they’ve totally saved me a handful of times during the mad dash that is summer physics!! I’ve found what works best for me is to watch the video, then read the corresponding textbook chapter, and then watch the video again. The first time watching it, it may not make too much sense. However, after reading the textbook chapter, it’s a super great way to gauge how much you understand and try to get a deeper/more dynamic understanding of the big concepts before moving to working some math problems. Good luck to all of the other physics students out there!!!

[@howHumam]

I am almost paying more attention to how it was presented than the actual presentation, she's so focused and intense yet holds an edge of casualness in her tone that might encourage me to interrupt her had I the audacity. Good job, please keep teaching.

[@samanthablackman4960]

you guys keep uploading stuff I'm learning at college 😂 from ethics to science 😂

[@Ph03n1X87]

Im learning at secondary school

[@notveryrea1]

@@Ph03n1X87 same

[@jarredc8929]

Whose quarantined and watching this for school?

[@madisonplays3756]

Me for science

[@porygon-z4503]

Did I just see Enter the Gungeon!? In Crash Course!?

[@vitamindubya]

Porygon-Z omg! Obscure reference that I understand on popular show or media!

[@jwbman]

yup

[@eddiesanders2719]

In settings, I put the speed down to 1.5

[@StickyTank]

i once did the double slit experiment, using a laser-pen and some tin foil. i was amazed when it actually worked and created a beautiful interference pattern on my wall :D

[@qilinxue989]

Interesting! How specifically was it set up?

[@pivotman64]

Let it be known that the people behind Crash Course play Enter the Gungeon.

[@jacksonmorton4915]

YESSSS

[@FiniteMan1933]

Yeah dude

[@supamayn17]

THANK YOU. I took a physics series and this was a perfect summing up of what I had learned about diffraction. I really needed a refresher.

[@G_Rad_Ski]

Ah, got to love waves without quantum probability

[@CorruptedN]

3:10 the single fact that the creators knew about this enemy in Enter The Gungeon implies that they got to at least the 3rd floor

[@maryamalhamdan1510]

My favourite thing about crashcourse is their into music

[@resqcreeper2]

love the ETG refrence

[@matthewhall319]

This is by far the best CrashCourse intro...

[@mrdfball]

You just taught me everything my teacher doesn't. Thanks

[@Intoxicatious]

Did you like the Enter the Gungeon reference? The game is on sale this weekend until January 30.

[@jan-Juta]

Am I the only one who gets the "enter the gungeon" reference in the animation at the beginning

[@curmudgeon7217]

yes

[@jan-Juta]

XD good to know

[@luxurious0346]

Yehudah Goldstein no

[@brento2890]

Perfect explanation !!!! I just replicated it with my smartphone flashlight, and some books. Works exactly as stated.

[@LeonNikkidude]

Bring back John Green for more entertaining Crash course history.I like the way he jumped on that chair to reveal mystery object.He cynisism was very entertaining.

[@nicdiculous]

It's interesting how a sizable amount of the comments are simply people trying to correct the video with their own opinion. I'm pretty sure Crash Course knows their stuff. So why act like you know things?

[@KyleCPM]

This could also be Refraction near the edges. Does the the coined light spot have a focal distance?

[@rkpetry]

(So many important questions on this topic)- Q#1. If a photon is shortened to a quarter wavelength (in an advanced optics laboratory), what is its total wave-cycle-count length for when it passes through a Young's Double Slit experiment-Does it still show 10± lobes on the photoscreen, or is it fewer lobes, (try it)...

[@yugeshkeluskar]

I was not able to understand this topic in my college and my exams are near. You put this video at the right time .... thank you so much crash course

[@rkpetry]

(So many important questions on this topic)-Q#2. What about the shape of the photon envelope keeps it on, its course, predominantly, (most of the photon instances traveling across 'empty space'), instead of doing the single-slit-thing; Would that shape thin out...

[@philoyphilia]

A 30-minute lecture was given in less than 10 minutes. Light is proud of her.

[@Mirsab]

im just studying waves, and light waves and light weight currently, perfect timing for the video Edit: I'm just studying waves and specifically light waves currently, perfect timing for the video. Sorry for the typo

[@Mirsab]

*light waves sorry for the confusion, it was just a typo

[@braxtonpal5842]

Really

[@darthcomo8387]

I don't know what is the most beautiful here faced with awesome gods art including this narator

[@nicolasmirandacornejo2614]

Congrats, my university recommended us to watch this video before entering the laboratory experience.

[@MusiCaninesTheMusicalDogs]

She's so adorable it gets hard to pay attention to the content. 😍

[@Monochromicornicopia]

Force carriers aren't "particles" in the traditional sense, instead they refer to quantities of energy moving through a field. Photons are quantities of energy that move through an electromagnetic field and gravitons are quantities of energy moving through a gravitational field. For example if you flip a rope, a wave of energy moves through the rope. In an analogy with light, the rope is the medium (the EM field) and the moving wave of energy would literally be light itself.

[@mrsimmons9451]

GDI all kinds of bosons, including photons and gravitons, are a part of the standard model, which include physical things that occupy space, can be interacted with and can't be split further. "instead they refer to quantities of energy moving through a field." You probably aren't aware of this fact, but energy itself is not some discrete thing that can exist by itself. It's the capability of matter to perform work, so it's misleading to say that it's "quantities of energy moving through a field". Energy isn't it's own object anymore than size and shape is.

[@kickhuggy]

this idea still blows my mind, I can't wrap my brain around the idea of an object being a subset of one object and a completely different object without these two objects being part of each other.

[@Sporkabyte]

Spider-manana I guess the best way to think about it is to take a leaf from chemistry's book and not try to jam it into one definition we already know (referring to resonance here). Rather, it's better to think about light as neither a particle nor a wave, just something else that happens to have attributes of both. Hopefully that helps :)

[@ayushaindas4948]

I love Crash Course

[@zakirhussain-js9ku]

There are 3 particle, mass, electric & magnetic charge. There are also 3 spatial dimensions xyz, 1 for each particle. Electric & magnetic changes have opposite counterparts therefore their particles can move in opposite directions of their dimension. Mass has no such opposite counterpart therefore it can move in 1 direction of its dimension. No physical entity can exist in less or more than 3 dimensions. Therefore for a particle to exist all 3 spatial dimensions must be occupied. Therefore all stable particles must have mass, electric & magnetic charge. To form wave particles must move in opposite directions. Since mass can move in 1 direction it acts as particle while electric & magnetic particles can move in opposite directions they act as waves. All stable particle will always exhibit wave-particle duality.

[@KyleCPM]

Double slit experiments are not slits in a 2 dimensional plane. Creating a slit also creates a wall to bounce off.on each side of the slit. It's more like a hallway than a slit. Keep in mind the light is entering into the hallway (slit) at an angle. This may simply be reflecting light. I propose a cross examination experiment. Mirror coat the interior of the slits. I predict greater brightness lines will occur, if so, disproving the former theory. For further clarification of where each effect is occurring from, coat only one slit. For greater clarity still, colour the mirrors differently on each face.

[@xdazamx]

Kyle Micallef So? The idea is that the light is parallel to that "wall" so it won't interact with it, in both wave and particle "form".

[@KyleCPM]

The light is not parallel. The hallway sized slit walls are parallel. The demonstrations are with a coneuler light source, diverging angles. Enabling much rebounding light inside those massive grand hallway sized slits. If the light was also parrallel it might passe without contact at all. Though magnetic divergence may occur with ionized light. I'll update the original comment.

[@davidsweeney111]

and God said let there be light light waves at God to thank Him praise be

[@dylanjones7472]

God said that a few days before he created the sun?

[@FMRovers]

Fox Mulder with his conspiracy theories... god...

[@vitamindubya]

Fox Mulder do you watch and comment on the same KZbin videos as me, fox mulder?

[@EagleZtoTheGrave]

heh...

[@sourcedrop7624]

praise him or die

[@LordOfNothingreally]

I have no idea what this pretty lady is talking about, but I sure am enjoying watching her talk about it *swoon*

[@amaranthine-one]

ENTER THE GUNGEON?

[@ProfessorYana]

Sure looks like it to me!

[@ZeeGhost713]

What is that?

[@caleblim6890]

"many of them thought light was a particle." I guess they're just particular about that

[@srrex2696]

How hasn't anyone noticed the amazing Enter the Gungeun reference!?great vid btw

[@Lord_Unchemael]

2:50 Enter the Gungeon anyone?

[@rofernina8311]

Yep

[@christinamanis4351]

agreed

[@magickisthekey]

Best explanation of the double-slit I have ever experienced! Thank you!!!!

[@Gaia_Gaistar]

Light Wave sounds like a c-list DC villain the Teen Titans would fight.

[@johnsylvester758]

she talks too fast. she's so smart

[@samahsalem6951]

watch her eyes at 1:25 shes reading

[@phenomenalphysics3548]

And beautiful

[@undertow4874]

Oh my God. Enter The Gungeon!!!!!!!!!!!!!!!

[@eddiesanders2719]

Actually, its cameras that work like eyes, rather than visa versa. Great presentation!

[@TazariaGaming]

I love how english speaking people pronounce things like the 'uy' in Huygens. It's actually pronounced the same way as the 'ui' in Kuiper from Kuiper's belt. For precise pronounciation Google translate 'onion' to Dutch and listen to the result.

[@tchikoumahmoud4665]

Your video just cleared the path for my billion dollar idea

[@PeacefulAnxiety]

Are you guys still planning on doing higher ed physics later on in 2017 or 2018?

[@gi0gi0_J]

0:05 heya gamers who’s watching this cuz of hw?

[@leninirshad7395]

i just didnt get it in a full semester engineering.lady just explained soo effortlessly i regret the time i wasted

[@srilekhaf493]

Can crash kids make a another video and slowing down everything and explaining words and terms?

[@rosecrux33star62]

I could watch her all day!

[@lucianmihail584]

With all due respect, this lady has no ideea when to stop, to let the information 'blend in' and to emphasize when necesary, i can't watch this, can not keep my toughts with the fast-talk and the lack of inflaxion in her voice; she should REALLY take some notes from mister Phil Plait - the astronomer (he had in my opinion, the gift of explaining things). In other words, i think Shini (this lady's name) is an inteligent person, just not a good pedagogue.

[@manas420100]

There's a thing called pause and replay, मंदबुद्धि

[@Godcatforlife]

um well it’s called *Crash Course* for a reason you know? And she puts a lot of detail into what she says making it better to understand and these videos are meant to be watched after knowing quite a bit as a recap, but I think you can learn from them too.

[@dipi71]

NASA’s Astronomy Picture of the Day 2018-10-02 _(»Supernumerary Rainbows over New Jersey«)_ sent me here. Cheers!

[@maverick.gaurav]

Greaaaat video...super cool animations make things like these really easy to understand. which I'm sorry to say, books just can't deliver.

[@jedigecko06]

Finally I get it! Huygens' Principle explains diffraction!

[@Ph03n1X87]

Light can travel about...300,000,000 miles onto my opinion

[@irvingchies1626]

how long until Nintendo strikes? make your bets below!

[@jessicaradford8564]

Oh man where was this three years ago when I did physics and was so totally lost on all of these experiments!

[@helium73]

The slit must be equal to or smaller than the wavelength. So to have the experiment be fair the slit must also be the same size as the ball. What happens if hole is equal to or smaller than the ball? A least the slit must be equal in size to the length of the particle. We know that electrons don't travel in a perfectly straight line. So why would we expect photons to do so? In fact if you shoot any light through an aperture larger than the wavelength the light will not form a pattern. It will behave exactly as if it's particles.

[@spijkerpoes]

so I mounted a coint on a stick and played around with a flashlight for half an hour. ..no bright spot in the shade. . ..if it disagrees with experiment, it's false?

[@littlejimmyxD]

spijkerpoes no its just way harder to see than this video suggests, look at veritasiums video, he demonstrates and explains it

[@spijkerpoes]

Cheesyfangs yea that's a great channel also.. ..but I can seem to find any video whatsoever about this coin trick. is it a meme?

[@spijkerpoes]

can't

[@TheAstrospace2]

spijkerpoes i agree i did the same thing with a coin and a light and nothing happens. I just see a shadow casted by the coin. I tried different distances from the coin to the wall and the coin to the lamp. I tried different flashlights and just nothing.

[@littlejimmyxD]

look for the video "The brightest spot of a shadow is in the center" (or something like that), he uses a ball instead of a coin. It is really hard to see with normal light, he eventually has to turn to lasers to make the spot visible

[@thanhvutien]

Very nice video. Could anyone know which video tool to create this video animation? Thank you.

[@hedving84]

what are particular rays of light? how do you know one from the other?

[@Redemmo]

I've found CC Physics difficult because of its emphasis on equations. I enjoyed this episode more, with lots of theory (even if I'm still processing it) and little or no equations. I know you have your plans for the course, but I thought I'd offer a bit of constructive criticism :)

[@OlafGodredsson]

+CrashCourse So does a higher amplitude mean there are more photons hitting the screen per time? Also, if it is destructive interference where two waves cancel each other, what happen to those photons? Its not like they destroy each other... Thanks, this has always confused me

[@lightsnackproductions918]

non-cuber watches this video: whoah, is that a 10x10 in the background?!?!?!?

[@stuffysnob]

The Light is love.

[@Rookblunder]

So the shadow is actually two light waves cancelling each other out. Learnt something today. Or just can't remember that part. Thanks for video.

[@cardayz1391]

I'm a little confused what we mean by light is a wave. Is light a wave like water (of course without a medium) or is light a complex wave given by Schrodinger's equation which describes probability of location?

[@afishhouttawater]

Could you make a video explaining sign, cosign, and tangent?

[@bakadominus5668]

it would be really cool to use this to make light patterns in cathedrals

[@nicolem2576]

very easy to understand. Thank you.

[@MI-lo2hj]

Honestly if u slow this down to 0.75 it sounds wierd put it to normal and u won't hear a thing

[@TheAwesomePieGuy]

What does the DFTBA at the beginning stand for?

[@a_little_bird]

LOL the sun at 6:30 is so cute

[@TrevorSchmahl]

Or are they corpuscles of light? Just read QED :p, I like the term "corpuscles" sounds kinda cool compared to particles.

[@djbslectures]

Doesn't the presence or not of the bright spot in the middle of the shadow depend on some relationship between the wavelength and the diameter of the circle?

[@jtera008]

I certainly hope that next lesson is: Light is a particles. Standard model: photon. One of finest a-ha moments of physics for me has been the realization that there is actually two ways to model light and both explain observed phenomena and yet are somehow mutually exclusive at the same time. Seems like we quite don't know all yet? Last time I checked the test result was; light emitted as individual photons did comply with these test settings and cumulative total of particles created expected patterns with min and max areas. In this lesson there was just basic wave theory nothing that would imply that there is other way to look at phenomenon. Still wave-particle duality explanation best describes all observed phenomena, doesn't it?

[@raheenrana7430]

Great timing, I've got an exam on this.

[@adityashukla1507]

most awesome video keep it up guys

[@nujissjiss885]

TSo that's why people like the color red for love, lust, attention, because it's long and low vibration. While blue or purple is a very high vibration and short altitude.

[@B_Son]

You mention how light also being a wave is one of the most important discoveries in physics during the intro but never mention why or finish the thought later in the video. Also there's a ton of terminology which has its place but I feel that there aren't enough similes for the layman to relate to.

[@mcitup1]

I tried to do the coin experiment to see if a spot of light to see if the dot would appear but it didn’t. I tried to find information on how to to it but can’t find any info on that experiment. Any tips on how to do it

[@SilveryK-v8q]

It always bothers me a bit when popularisation says that light is "both a particle and a wave". It's neither. Objects described by quantum mechanics are their own category of non-intuitive things, and while they do have properties that remind us of the older, classical paradigms, that doesn't make those paradigms fit for explaining QM.

[@zack14d17]

can you make a video explaining, why do your words travel close to speed of light? i try to watch your channel but can’t catch up with your pace.... then i have too turn on the sub title, which too seems to pass faster than the speed of sound 😠 explain this.

[@oldcowbb]

good, good, i can feel the modern physics

[@maverick.gaurav]

oldcowbb this is like the most ancient optical physics there is 😁

[@oldcowbb]

it's coming, it has to be

[@kickhuggy]

Gaurav Nema this idea is taught in a class that's generally called 'modern physics', which is kind of intro to quantum. it's after physics 2, it's a tough class

[@maverick.gaurav]

Spider-manana Yup..I agree...modern physics has a very different and difficult ideology..😯 that ancient thing was just a joke bro 😊

[@kickhuggy]

Gaurav Nema ooh, I didn't realise

[@ildikoki]

could you guys do a video on opaque materials and shadows?

[@benjaminnelson5455]

So, how does this agree with the rule that you can't create or destroy matter or energy? At the macroscopic level, the varying intensity of each spot I imagine conserves exactly all the energy, but what about at the quantum level where there are still photons involved even though the double slit experiment sacrifices the ability to pick them out? The photons can't collide and vanish into oblivion, and some versions of this experiment prove that they don't. Is this evidence for pilot wave theory, or is there more to it?

[@camerondion9201]

Light confirmed wavy

[@Danisharain7869]

Can u list down the principal of light wave

[@RoccosVideos]

I like her accent. Also the content was interesting as well.