Dispersion | Geometric optics | Physics | Khan Academy

[@femiairboy94]

Why can't​ they just be this clear in college?

[@ΝικήταςΜακοπουλος]

femiairboy94 exactly the same at school. Teachers are meant to confuse students with all those complicated terms and formulas

[@iBuyBitcoin]

Why cant KZbin just be the new college ? Lol

[@odasakunosuke5137]

@@iBuyBitcoin well it is, as of now XD

[@manishzare7735]

Clearance of all concepts about dispersion in 2 min.

[@lucyx8299]

Its like Khan Academy reached into my brain and looked to find my exact question to answer it!

[@gabriellobo3456]

Thank you. This video was quick and bang on point.

[@kennyperez1085]

first time i've been mindblown . this is how physics should be taught.

[@danielharris3263]

Nice and succinct

[@musahabeshi1539]

Thank you, very useful.

[@NotLegato]

wonderfully clear.

[@anubhavsrivastav2150]

Excellent explaination

[@Truth_Seeker567]

So the shape does not have any role?

[@jkgan4952]

Very well done video!

[@nathan791]

Love this

[@arishaashraf7784]

Then why doesn’t dispersion happen when we pass white light through glass?... I mean why does it work only with prism?

[@alansmithee419]

This is because of the different angles between the two faces of the prism the light passes through. In a window pane, the light enters one side and disperses inside the material, but when it reaches the other side and exits, all of the wavelengths are turned back the other way by the same angle they were refracted by upon entering the glass, because the two sides of the pane are parallel to each other. This means the light, though slightly more spread out, is all parallel again. The amount it disperses is limited by how long it was inside the glass for, and may not be enough to notice by eye. And for non-laser light, red that entered one part of the window will simply match up with purple light that entered a different part, so they'll exit together. This makes the output white light that's just been mixed up a bit. In a prism, the exit surface is at a different angle to the surface the light entered through. The light disperses upon entering, but then due to the difference in angle between the surfaces, actually disperses further upon exiting. It then spreads out further after leaving the prism, allowing it to be easily seen by placing a display screen a few meters away from the prism, a distance over which the light can spread out considerably.

[@odasakunosuke5137]

Thanks

[@karcicegi5366]

thank you so much

[@angelikaimtiyaz7280]

What grade do y'all study in??

[@Kapil-jsw]

10th

[@Lukas-qn6to]

Thank you! I'm from Germany and didn't find a good short german video about this topic. I'm not very good in speaking english but I totally understood it. Is "in" correct? Or is it "at"? :D

[@metastag]

I think 'at' would be better, but 'in' works as well. :D

[@Lukas-qn6to]

@@metastag Okay, thanks a lot. :)

[@metastag]

Bitte! (Welcome in German )

[@beoptimistic5853]

kzbin.info/www/bejne/joKsk6FobMmCoKc 💐💐👍👍

[@kinocubing5389]

Im sorry. but did he say that higher the refractive index, the smaller the angle of theta. Does that also apply with the colours? Im kind of confused

[@petergoh5628]

Is it possible to make the violet light bend on top of the red?

[@laxmiparida4119]

Every light has a certain wavelength, for that certain wavelength there is a different index of refraction since you have mentioned red and violet.. let's discuss about it; The red light has the more wavelength and the violet has least wavelength! So, red has less energy than violet since, wavelength is inversely proportional to energy...If you take visible light, that is let say sunlight even though there is a small amount of UV light in it.. let's just ignore that..If we incident the sunlight onto a glass prism, The visible light is made up of seven wavelengths, and since every wavelength has a different refractive index or those seven wavelength bend differently, so they disperse!!! Because they are entering from a rarer medium to denser medium....So, due to this the red appears above and violet appears below that is violet makes a lesser angle with normal while red makes comparatively biggger angle with the normal..

[@alansmithee419]

@@laxmiparida4119 Having different refractive indexes does not mean violet must appear below, it could also appear above. It just happens that most materials have positive dispersion - i.e. higher refractive indexes for shorter wavelengths. Some materials have negative dispersion, in which the violet will be bent less than the red. Some other issues: - Visible light is not made up of seven wavelengths, it is a continuum. If it weren't, rainbows would appear as 7 thin lines of precise colours, rather than as 7 bands of colour all appearing to merge with one another. - refractive indexes have little to do with density. While single materials may well have a relationship between their density and refractive index, between materials there is little correlation. A material may have a much higher density than another and still have much lower refractive index.

[@laxmiparida4119]

Oh! I appreciate you're reply! Yea ofc, the refractive index has a lot to do with the material it is made up of! It depends on the energy packets of the atoms of the material and how much exact energy do they Need to Excite electrons! I hope you understand what i am tryin' to say....Also you're Right that mass density is different from optical density which derermines the refractive index! I am eager to know what is continuum? I guess the merging of the colours has something to do with our detection of wavelengths! The fact that we Are able to see colours of rainbow is because the wavelengths Are entering n'on parellel and Are stimulating the impulses in the cone cells of our Retina at different points or what if these wavelengths just get converged near to each other at Retina...so it seems to us as merged!...I would love to get to learn about continuum and you're knowledge on merging colours of the rainbow!

[@alansmithee419]

@@laxmiparida4119 Continuum essentially just means that there's no fixed set of possible wavelengths. A discrete set would be something like "only integer multiples of 1nm wavelengths are possible" (so 1nm, 2nm, 3nm etc) which is the case for some quantum systems but not for all light in general. Thermally emitted light such as that from the sun is an example of light that has a continuum of wavelengths. Continuum essentially just means the wavelength can take on any value: 1 nm, 3.24 nm, π nm. Anything. I was careful about my language, but apparently not careful enough, which I apologise for. By "bands of colour all appearing to merge with each other" I meant just that - they *appear to* merge. In reality this is just the effect of the continuum I described above - there is not simply red light, then orange light etc. There is a continuum of colours between the two, all of which have their own wavelengths and therefore their own refractive indexes within the material, so they spread out to form the rainbow. To our eyes, these colours appear visually "between" red and orange, so it *looks like* the two colours are mixing in this region, when in reality this region contains different colours that appear to be a mix of the two to us.

[@laxmiparida4119]

@@alansmithee419 yea i do understand discrete set! Like that of charge! That charge cannot take just any value but discrete values! Woah! I didn't know about about continuum! Yea so in a nutshell, it's not all about what we see! The only band if colours which we see is 7 wavelengths,, which our Are sensitive of! But this was quite a good info! Thanks!👁️👄👁️

[@aisha.s614]

Nice explanation :-)

[@ivanpedro9151]

and so basically, theres an angle where the dispersion of light rays reaches its critical point, the point of total reflection in our eyes... does that mean theres an infinite number of colours we are just simply incapable of seeing or am I just triping?

[@thatomofolo452]

cool

[@goddess_ofchaos]

i dont get why theta 2 becomes smaller if n2 becomes bigger. sin(x) is a continuous periodic function, so unless the "borders" of theta is specified as 0

[@alansmithee419]

Well just think about the implications of that not being true. Since theta1 is relative to a line which is perpendicular to the surface of the object the light is entering: If theta1>90, the light started *inside* the water, not outside, so you're asking a different question. If theta1

[@ZayaKRS]

i wanna know the exactly refraction index of each color and how to find it

[@wumbology8421]

It's just the speed of light divided by the phase velocity of the color.

[@0soinspiring694]

❤️🥺

[@minghei2010]

如果計算機在使用時 知道 數值 可以求sin幾度嗎?