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.

Do you speak another language? Help me translate my videos:

Music Attribution
Title: String Theory
Artist: Herman Jolly

All of the images are licensed under creative commons and public domain licensing:

[Hongsen]

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

[tbcbruno]

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

[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.

[samtheexplorer]

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

[snip-sniptear]

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)

[guillermofleitaspulido]

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

[mayanksingh]

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

[SatishPandu-tkqr]

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

[stephaniehernz]

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

[titanicstuff]

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

[michellehammar]

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

[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)

[Aseelisthequeen]

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

[chikin.nugiesss]

Much better than learning at school for a month

[LawatheMEid]

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

[taskeentori]

Your videos make things clearer.thanks!☺

[jasonjente]

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

[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!

[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.

[cgm]

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?