Total internal reflection | Geometric optics | Physics | Khan Academy
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- čas přidán 6. 09. 2024
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Critical incident angle and total internal reflection. Created by Sal Khan.
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Man, why cant i have teachers like this? Mine just sits there and talks like i can imagine what the .....*.... he is talking about. Thanks.
Same💔
i love how he hopes we find it "reasonably interesting," lol. not "incredibly" interesting or even "very" interesting. just "reasonably" interesting. :D
@Enrique Duran Mynenko yes
@Enrique Duran Mynenko You just asked me five days ago bro.
Alive?
@@omaralsaheb9737 bro 😭
once again, I don't know what would I do without your videos. so much love to you Mr. khan
1:26 to 2:45 is what i found most useful, thanks mate
Thank you, Mr. Khan! You are the one who helps me to escape from my boring physics lesson!
0:38 i love that you always have such good examples to explain such phenomenons. this has actually something to do with the wave character of light. the example with the car is perfectly fitting. the light reenters the medium it just left due to its diagonal micro movements and looses speed. reentering the fast medium again, it made a curve.
thank you so much ! I litteraly study in french and english is not my first language and i’ve learned more from this video than from class😭😭
I swear no one teaches like Khan Academy!
This is amazing, I had been trying to understand this whole concept from other videos, but for some reason, all those teachers or speakers assumed that everyone is a genius and automatically knows what they are talking about so instead of explaining, they just carry on saying a bunch of words that I have never had of.
thank you! this video better my understanding :)
This wil help me so much for my physics test tomorrow!
Thanks a lot. My teacher made the explanation complicated. This sums up what I need perfectly.
Sal, you are a lifesaver! Summer classes have us learning this whole playlist in 3 days and it's going to make up around 25% of the final. I was so stressed but 3 hours of sitting down and watching this playlist actually makes it manageable. Thank you, thank you, thank you!!!
I need my teacher teach like you,interesting and easy-understanding
I want to keep it simple. You do great!!
Thanks for this video, helped explained this better rather in class. Fully understood the concept behind critical and total internal reflection. - grade 10 student
Where have you been all my life *sigh*
Thxs a million!! Khan Academy videos have been helping me for 2years now! Sal's the best at making complex things simple!!
waaay better than my teacher. I love khanacademy
Thank you SO much! This has been immensely useful and makes far more sense than it did before I watched the video! Many thanks
Once you had explained total Internal reflection, I whipped out my scale and even tried it in practical....and it worked....Thanks for explaining in ruch simple words and making it understandable
This was the one part of my optics subject in school i never understood. Thanks for explaining clearly!
I appreciate the analogy of the car going from one surface to another. That's an easy one to remember.
I found it reasonably interesting! Thanks! :3
You have carried me through my GCSE's
My teacher has been explaining it for the past hour and I had no clue what she was saying. I understood right away after watching this video!
i love your voice and teaching skills Sal, thank you so much for taking the time to make these wonderful videos you are awesome
Oh my God, they never told us where the 1 comes from!! Thanks a lot! ^^ You're so awesome! :D
The core has a high refractive index and it is surrounded by cladding that has a very low refractive index. There is a "cone of acceptance" (where you seem to have gotten confused; the air to 'glass' transition is not fundamental to internal reflexivity) such that for snells law, rearranged and sin90->1
crit. angle = sin^-1 (1 / huge n). the argument approaches 1/inf. and sin inverse of zero in 90 degrees.
That is to say, that only if light approaches at 90 angle will it escape. :3!
Thx!!! This helps so much I hope I wont fail my physics exam
The way u explain is top man 👌👌
bless you sal
Youve helped me in so many of my classes...... i hope you know a lot of people really appreciate this stuff. Thank you. Thank you so much.
Is this what causes all reflection? Do mirrors, for example, have such high refractive indexes that they reflect all light?
That is a very good question
This really helped a lot, I'm 14, i need to learn this in foreign German though :c this is going to be so hard xD
NZVON where did you come from?
Arolema Prarath wat
Thanks a lot..!! It was very helpful 😁..
Thaaanks , that was really helpful !
woah
This is a really great vid, I just have one quick question...
Snell' slaw states that Nr=sini/sinr, but with TIR the critical angle is sini so it becomes Nr=sinr/sini. Do you have any idea why it flips? Thank you!!
That's just confusing bro :)
Jj Lortez LOL I know! My freaking physics exam -_-
Learned more in 6 minutes than an hour with my college professor... thanks so much.
Reasoning it out, your explanation from 0:28 onwards was fantastic - it just immediately clicked. Thanks for your help!
So is it safe to assume that regardless of the media the ray is initially in and the final media it is in, we can use the media with the lower index of refraction in the numerator, and the higher index in the denominator? Because there's been a couple situations where I get undefined errors in my calculator. For example when a ray goes from glass to air and I use the glass in the numerator and the air in the denominator because I'm thinking n1 = glass since it was in glass first.
This is great! Havin a physics test tomorrow! This really helped me to understand what TIR Is!
These videos are the only reason that I'm able to pass my physics exam.. THANK YOU SO MUCH!
Thank you very much i have a test tomorrow and i didn't know how to do it
MODY 14 me 2
+MODY 14 me 2
super AmaZing.....I'd rather bunk college and sit at home and learn from you......You"re amazing!!
Great video for understanding reflection,refraction and critical angles!
A good point but sin(θi)/n cannot be greater than 1. No material has a refractive index of less than 1 and sin(θi) cannot be greater than 1 which means sin(θi)/n will always be between -1 and 1, inclusive.
Hence, Snell's law is valid.
In our case -1 ≤ a ≤ 1 and b ≥ 1. And so, -1 ≤ a/b ≤ 1.
thank you! It only takes me 8 mins to understand what total internal refraction is. I can't even figure out what my teacher is teaching before watching this video.
Thanks you very much for the video I was facing trouble understanding total internal reflection...... Thanks a lot
Thank u! This helps me a lot doing my school works! An amazing and engaging lesson!
Most beautiful channel i have ever seen.❤
Thanks a lot man! I have an exam tomorrow, and you just helped me understand Snell's law and the whole theta critical thing a lot better!
Wow dude it’s been 8 years now u would be doing a job now right?
Dang now its been 10 years
7:24 is a glitch in real life
3:29 also glitch
7:39 another one!
Thank you so much, you made this waaaaay easier
Respect🙌🙌
Sooooooooo helpful, my exam is tomorrow and this is really going to help
The car example was brilliant
This is awesome explanation!
This makes so much more sense!
Thank you SO MUCH!!!! This helped to explain the concept and reasoning of the critical angle.
I love this guy's calculator 😍
You're a life saver Mr. Khan. Now I know I won't fail my physic exam.Lots of love 💜
Sal Khan is the GOAT🐐
Thank you Khan Academy... You guys are always life savers !
ooooooooooooooooooohhhhhhhhhhhhhhhhhhhhhhhhhhhh 1:40 shoot I GET IT now!
thank you so much,you are the best Physics teacher in the entire world!! by a student from HONG KONG
That's a great programme...
It helps me a lot!!!
this guys a champion
How do you calculate the things you do??
what a concept of fiber optics wow amazing thanx alot
This video helped alot!!!!
helps me alot. thanks!
Thank you so much!! It all makes sense now!
Good
The best explanation ❤️👏
Thank you so much, you really helped me for my test!
very good . Thank you so much.May Lord bless you
right through d basics ! nailed it ! Sal u rock !
so is it that if incident angle is karger than critical angle then total internal refraction occurs?
Thank you Mr.Khan ,your videos are very helpful .
sir you just saved my life
i.e by snells law sinI/sinR = n, then R = sin-1( sinI/n), but what if sinI/n is greater than zero, then there is no such thing as Sin-1(x>1), and so Snell's law breaks down.
But If snells law breaks down then how could it be mathematically valid?
Thank you so much
thank you so much was very halpful😉
Cleared things up for me, thanks!
Thank You
thank you so much, man. my teacher has such a strong German or Austrian accent and its hard to understand anything thanks so much
n cannot be less than one. The refractive index of a vacuum is 1 and no material can have a refractive index lower than vacuum.
I don't understand why light totally internally reflects in fibre optic cables. The light is going from fast (air) to slow (glass), so wouldn't the light bend towards the normal (or towards the walls of the cable).
I am assuming that the walls of the cable are glass?
helped me out alot. Thank you.
I see what you mean now. Did you watch the video? It explains what happens when θi becomes greater than the critical angle - you get total internal reflections.
Snell's Law is still mathematically valid, given a certain set of circumstances.
Thanks a lot for this video! It's nice to see you're constantly uploading lots of videos. Many of them are so helpful! Thank you so much for keeping this channel up and going.
@arenms believe it or not many people enjoy reading / learning. I read an article about khan and his academy in a magazine a while ago and he appears to be a very humble guy genuinely wanting to help others. He enjoys reading which is how he learned all this stuff.
And honestly what he teaches is relatively basic stuff. Im a medical student and now that is mentally / physically draining.
you are a GENIUS! Thanks alot
Thank you ，that was really helpful
well explained
thanks a lot!
4:50 u can just calculate it with ur calculator and put the unknown given as an X
How do you display the calculator?
Nice explanation 👌