Refraction of Light

120 - Refraction of Light
In this video Paul Andersen explains how light can be refracted, or bent, as it moves from one medium to another. The amount of refraction is determined by the angle of incidence and the index of refraction. Snell's Law can be used to calculate the angle of refraction. When the angle of incidence exceeds the critical angle it will result in total internal reflection.
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Music Attribution
Title: String Theory
Artist: Herman Jolly
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All of the images are licensed under creative commons and public domain licensing:
Beltz, Ellin. English: Main Street Ferndale, California Refracted Upside down in a Contact Orb Juggler’s Crystal Ball at the Victorian Day Event., November 22, 2014. Own work. commons.wikimedia.org/wiki/Fil....
Graf, Friedrich. Deutsch: Illustration “Totalreflexion” Basierend Auf “Total Internal Reflection” - Für Die Miniaturdarstellung Optimiert., March 20, 2012. Own work. commons.wikimedia.org/wiki/Fil....
Inaglory, Brocken. English: Green Sea Turtle, Chelonia Mydas and His Total Internal Reflection., 2008. Own work. commons.wikimedia.org/wiki/Fil....
JrPol. Nederlands: Refractie in Een Glas Water, February 22, 2015. Own work. commons.wikimedia.org/wiki/Fil....
“Refraction.” Wikipedia, the Free Encyclopedia, April 2, 2015. en.wikipedia.org/w/index.php?t....
USA, Quinn Dombrowski from Berkeley. Marching Band, June 30, 2013. Marching band Uploaded by Anastasiarasputin. commons.wikimedia.org/wiki/Fil....

[@Hongsen]

That's​ a point I am looking for . Finally i have able to understood why bending of light related to the speed.

[@anteconfig5391]

what speed though? that is my question. is it the speed of light in the medium? or the frequency of light in general?

[@anishtiwari1121]

Every school should show this.

[@gdslowingunicorn1806]

Mine is :)

[@tbcbruno]

thank you i learned more in 10 minutes than in a month of class

[@itznotjes185]

It’s been 7 years, how’s life been treating you

[@Catlover-yi4cw]

@@itznotjes185 lmao 8 now - and 5 months for you, how’s life been treating you ?

[@snip-sniptear956]

Thank you so much! I had to read the chapter and come back to this video several times to understand what exactly your illustrating when light-slows-down when it goes towards a denser medium (grass) and how light-speeds-up when it goes from a denser medium to a less dense medium (air)

[@Aseelisthequeen]

You're amazing! I appreciate your videos so much, not sure how I would've gotten through school without you!!

[@pipMcDohl]

the moving band analogy is great but i would have appreciate a lot if there was an explanation why light is working this way. one photon is one, he is alone, not four marching side by side.

[@opulo1]

Photons usually come in groups, as for why it's changing it's angle, the photon creates an eletromagnetic wave so changing the medium where that wave travels where it's harder to move the eletrons like water, this slowdown shifts the wave at an angle, at least it's what I've understood from studying it.

[@DanielPilloff]

The wave front doesn't have to maintain same distance, but it does remain in phase. See physics.stackexchange.com/questions/558397/can-a-light-wave-front-narrow-or-widen-in-refraction-and-what-does-this-really

[@samtheexplorer4737]

i literally learnt more things in 11 min than 6 hours in class lmao

[@ivankoh3779]

chen peiliang ikr ;D

[@AakashDoshi2003]

same

[@sarahvazquez7736]

Literally

[@Will-os1zd]

same

[@thedangerplayer5029]

chen peiliang yeah dude😎😎😎

[@michellehammar3555]

Yes! You just saved me one day of studying! Like Chen said; learnt more in 11 min than in 6 hours of class!

[@guillermofleitaspulido]

This way of theaching is amazing, it should be a global standar!! Thanks for this videos Paul!!

[@titanicstuff2103]

The best explanation I ever got about refraction. Thanks a lot!

[@melonheadyuki]

Thank you so much! This was so understandable!

[@jasonjente6793]

Amazing video, it really helped me remember al the stuff I learnt from highschool! Really great and on point examples, thanks!

[@taskeentori9883]

Your videos make things clearer.thanks!☺

[@nattinattson9562]

Thank you for this video! :D Really liked the marching band metaphore. It made everything easier to understand

[@duazia9737]

I love the analogies! Helped me a lot! Thanks!

[@SatishPandu-tk2qr]

this is the best video i saw till now about light and how it behaves thank you

[@mayanksingh6916]

hi sir...... i want to thank you because your lessons helped me a lot......you also give quality of content and i hope your channel rises.....i wish you would have been my science teacher ;) (i live in india)

[@acesagayno]

Finally. The video I've been looking for.

[@pauldong]

I love the marching band explanation, it is the best definition for refraction. Other people will just, it changes speed, oh my god, but they probably don't even know the real reason. (*cough* *cough* science teacher)

[@kronkite1530]

Not according to Fermilab

[@chikin.nugiesss927]

Much better than learning at school for a month

[@craigcoates6247]

AMAZING, educational gold mine

[@renatao6330]

Best explanation I've ever seen.

[@nineeleven9455]

How do you translate the marching band metaphor to light rays, as in, how does the part where the band members want to stay the same distance side to side relate to light rays? Thanks!

[@DanielPilloff]

The wave front doesn't have to maintain same distance, but it does remain in phase. See physics.stackexchange.com/questions/558397/can-a-light-wave-front-narrow-or-widen-in-refraction-and-what-does-this-really

[@winstonsoh5255]

it is extremely helpful.Thanks so much

[@jaishetty8586]

one of the best lectures in optics.

[@arifbillahmeskat1724]

Thank you so much sir

[@keonahandumon2322]

Thanks so much! I never really understood this lesson but you made things clearer! ☺️☺️

[@SHADOWGAMING-fl4wf]

Yes 🥰 me too ❣️

[@pikasup1696]

That analogy is ingenious. I understood light in an instant

[@JihadAlAnsari]

Thanks, this is awesome

[@randomstoday]

you are literally saving my life

[@olivier671988]

Hi i know that, due to the gravity, time is slower near massive object. I wonder if the effect of time distorsion is "equivalent" to the effect of transparent material (that you represent as sand) ? I know that in optical fiber light is bend by passing through a medium that has a gradient of indice. Is this effect the same when light passes through the gravity gradient of a star (so the light is bend too) ? Do you think the analogy with a tank turning by modifying the speed of its tank tread is worthwhile ?

[@wexer82]

you're an amazing educator. thank you.

[@andBassandSwing]

Fantastic videos, thank you.

[@icici_]

how did i learn this whole concept in an 11 minute video compared to a 3 hour class, which I understood nothing lmaoo. Thank you so much !!

[@parthsuyal5879]

thanks!!Wonderful!! Now I understood why light bends by the example of marching band.

[@foreverboey]

This is sooo helpful! :)

[@usaamabid4994]

This is really awesome

[@havardamundsen901]

Hah, this was awesome. So easy to understand :D Thank you!

[@phantxm7699]

that marching band analogy really helps

[@k0be55]

Appreciated

[@Psyche.197]

amazing explanation!

[@stephaniehernz]

studyig for the mcat and this is so helpful. Thank you sir!

[@anindobagchi3408]

That was extremely helpful

[@joudabudan4562]

thank you so much i literally learnt from you more than my prof

[@SatishPandu-tk2qr]

Thank you so much sir, especially for refraction analogy 04:40 to 05:40 Thank you sir....

[@mohfa1806]

Hello, thanks for those great videos.....i have a question : when light passes from air to glass it bends as in the video , so why we don't see colors since it bends and velocity reduced ? .....thx

[@AshishKumar-jv6nj]

So good explanation

[@camygiuliani8758]

fantastic video ! Thanks :)

[@LawatheMEid]

And what about the analogy of the critical angle? How to explain the synchronous between the photons in their marching?!! Thanks.

[@ian.ambrose]

Thank you, professor.

[@notadoctoryet6040]

He helped me in bio, he helps me in physics. My guy is the Jesus of science.

[@thedisintegrador]

Yes he is miraculous

[@mhansl]

Amazing lesson.

[@rdotkey]

In the video at about 2:40, we see the beam being bent towards the normal, which would indicate n_2 greater than n_1. That means the light is slowing down as it goes from material 1 to material 2. Paul then extends this to Critical Angle, which happens when n_2 less than n_1 - not the way it is shown. Think of this as when light coming from under water is going into air. The index of refraction of water is greater than the index of refraction of air. So for angles near the normal, light moving in this way would bend away from the normal, because it is speeding up at that transition, and this could then be extended to critical angle. Otherwise, such a good video!

[@rmeducationcentre9435]

Very good explanation....

[@AhmedAli-qd1hu]

That was awesome😊

[@feelingzhakkaas]

Nice video, thanks. Do you have videos on 'why the speed of light reduces in dense medium' ? What is the reason for slowing down? is its interaction with medium atoms or something?

[@Will-os1zd]

Thank You so much for this it helped me on my science fair project

[@taliawang9425]

Hi, but may I ask, to which degree does the light bend? because I don't see a specific degree that the refracted light can bend towards. For example, for the law of reflection, light reflects the same angle as the incident. Therefore, what would be th especific angle for the refracted light ray?

[@malekmalouka305]

That was very useful thanks.

[@anthonygachoki9262]

Can't believe there is a dislike on this video maybe those professors

[@DownhillAllTheWay]

At 10:56 - "remember, they're going to keep the distance between them the same" They can't. If we are marching, say 1m apart, and the rank in front of me slows down, then I am going to get closer to the soldier in front.

[@DownhillAllTheWay]

@Nate Borg Yes, I agree that it makes sense. I was just nit-picking about the distance between band members. They, of course, can be trained to alter their behaviour, whereas training light waves is a non-starter. But just as the band members get closer while they are marching slower (in the glass), the light wavelength also gets shorter, then expands to normal again when the light exits the glass.

[@caroline8239]

Thanks so much for these videos they are more helpful than my teacher :/

[@willingoYT]

That was amazing. The only things not immediately evident are the snowglobe's inversion of light and the total internal reflection from the turtle, but those were side comments anyway.

[@monight9631]

Such a help full video thank you

[@Suesco]

what im trying to understand is by what mechanism do the marchers have to stay equal distance apart? what stops the waves from breaking down/spreading out? doesnt this mean that light waves have some kind of tension holding them together laterally? is it the magnetism?

[@zohartrainin4493]

Can there be a state where the angle that the beam hits the surface of the water (the beam coming from the water to the air) is an angle larger then the critical angle and the beam will be both reflected and a bit transmitted into the air?

[@MonkeyDLuffy-xr4fl]

As a chem major, I totally though n=c/v at 3:07 was concentration, and I was amazed for a moment xD

[@prateekjain81]

Yes it was very helpful .Thank you very much

[@rudrasingh-vy4th]

how did you go from theta2 = sin -1 .577 to 35 degrees. I don't get what operation I should do to convert .577 to 35 degrees

[@TheHHPodcast]

this is amazing

[@EagleSlightlyBetter]

what is the link between the members of the marching band and the wave of light? Are the band members photons? Why do they maintain spacing in the rows but not the columns?

[@sopwithcamel5519]

But doesn't light move at same speed always? What do you mean it travels faster through one medium than another?

[@ToMinecraftAdventure]

Cant wait to use this in my everyday life..

[@strategen9124]

Jose Calderon knowing about the laws of the universe and how it works is supposed to give u pleasure

[@strategen9124]

Jose Calderon by satisfying your curiosity

[@kappnspacey8664]

i feel it

[@argrusvfx1582]

Im watching this to revise for science, i got an exam tomorrow haha

[@balreddy7929]

Sir do reflection and refraction occur at the same time?At a glass surface

[@zu5926]

It was very helpful

[@yashadizero]

Thanks

[@cgm778]

I like the marching band analogy. I get that the sand is analogous to the material. Sand slows down marching because some gets displaced with each step, but how is that analogous to what slows light down?

[@jollyjokress3852]

*Why doesn't the first one that enters the sand push the ones to his right so distance is kept?* Couldn't he just go in straight and the others become slower once he enters the sand? (I bet it has to do with lowest energy state).

[@fortniteistrash1150]

Learnt way more than a tutor could teach

[@gabrielneibrief5298]

I think I might actually pass my Chemistry final tomorrow!! Thank you so much! :)))

[@SHADOWGAMING-fl4wf]

Nice one 🐱

[@thebrats267]

love the vid

[@anteconfig5391]

Hi, sorry, 2:52 n=c/v you say "v" is speed, but what speed? The speed of the medium through space? or do you mean frequency? 3:04 "Because the index of refraction is equal to the speed of light divided by the velocity" my question just is "what velocity?"

[@subrodeb9085]

Superb Sir..Thank You

[@lookatme7032]

That analogy seems to suggest that when moving from rarer to denser medium a part of the light is moving faster than C.

[@mridulboro7467]

Waow it was amazing. Learned a lot. Thank you so much sir.😁

[@snoitseuqpi1119]

Question: Are objects technically every color they absorb, or are they the colors they reflect? Perception wise I know we see what is reflected, but as far as energy, would a leaf be every colour but green, due to it converting the rest of the energy being used to make the leaf? I am trying to understand colour absent of our eyes, and on a energy basis. Colour doesn't exist absent of light, and then the physical properties (including the energy levels of the atoms) will also change the way an object reflects colour (i believe vanadium and mercury depending on physical energy applied will change from lower to higher energy states and back as electrons jump, and chang colours accordongly). I just want to know, could objects be more accurately described as the light the absorb, or in all definitions are objects defined only as the light the reflect? And also could a light source change a physical property of an object (adding energy to it) to make it reflect more or less of certain wavelengths (eg diffuse/ambient vs high energy photon beams)

[@TemeraireBjartskula]

Marching band! I should remember that one, that would really help me remember in which way to go XD

[@argumentumtv8132]

Thank you for showing how light bends (hard edge) and not curves

[@MarwanKhan]

Thank you!

[@ashfiaash1749]

Sir do you know how much did this video help me?! Thanks a lot!!

[@Devta113]

Thank you for the match band.

[@parthpathak4490]

great analogy

[@LowtechLLC]

If the light slows down why does it stay red? How come 650nm doesn't become a shorter wavelength? If air to glass has an index of refraction of 1.5, shouldn't 650 nm / 1.5 = 433.3 nm = blue. What am I missing?

[@akees2799]

Color depends on the wave's frequency rather than it's wavelength. Frequency remains constant when light travels through different mediums. The speed, however, does change and so does the wavelength according to Speed=Frequence x wavelength.

[@gregritchie1758]

best type of glass for passive solar panels with fixed plane facing south?

[@Bangy]

Thank you for helping me paint water

[@adityapranav6578]

Thanx bro this will surely help me in my ot exams

[@princesinggh]

You told us how's the Icecream taste But you have not told us. What it is actually made up of...😂

[@dhrubajyotidutta3297]

Y'r awesome man thx😁

[@RuslanLagashkin]

But why do they try to keep same distance between each other? In the same simulation, if we change the representation fron "ray" to "wave", the diameter of the light ray changes (in a same way the objects appear magnified aftet going through the glass of water in the beginning of the video).

[@azharamin14]

can u please tell me tht why light bends towards the normal... wht is it awaay to normal