Why does light bend when it enters glass? 

I appreciate your comment appreciating the creator's appreciation of the comments.

Zachary Collier I appreciate your comment appreciating Flying Skyward's comment appreciating the creators appreciation of the comments.

I would really appreciate if he could explain to me how that explanation would work with a TE polarized wave (look for my other commentary).

@@stevenutter3614 I appreciate your comment that appreciated the prolonged thread of appreciation, as I realized how I assured the right spelling too :)

@youareonthetube1 Have I just seen a different video from yours? I did not hear the word "lie" in it. He does not talk about conspiracies here. All he is saying that some people in an effort to explain things to lay people (and themselves) are wrong or incomplete. Has your physics teacher when he talked about gravity explained curved space to you? I do not think so. In making things easier some people get too far with simplification and others have not understood the matter themselves that they are trying to explain. Science is about falsifying wrong hypotheses and explanations and that is exactly what this guy has done. Please tell me in what publications in scientific magazines you have spotted fraud and misinformation and proove to us what is wrong with it. Just saying that lies are getting spread without showing what and where is dishonest.

Watch some of Leonard Susskind's lectures where he will give you a glimpse of how stuff really is if you have an appetite for more. You won't know how to do the math but you can follow his arguments as he goes through them and will come out spellbound.

Ditto! I'd honestly rather watch your videos than Neil deGrasse Tyson's or Leonard Susskind's! (Maybe because I'm more interested in quantum physics than astronomy, for the former, and because you work from scripts, for the latter.) Maybe not more than Sean Carroll, though. Oh, but if you could do a feature-length documentary _with_ Sean Carroll, that would be incredible!

+1

yeah me to

I emailed him one time and he told me he has lecture you can find them at the Great courses plus website under Dr Don Lincoln.

Me too , some professors like HC Verma etc explained , but they were wrong too becoz they used the Huygens principle which is indeed impractical

Baat to sahi hai lekin hard core physics wala answer samkh me kuchh nahi aya .

Hi indi

Yahi to Indian Education system ki khasiyat hai

@@akanshavishwakarma272 ?

DotaLove I also asked this question in the 9th grade I didn’t get an answer until now. I am 70 years old.

So true they always told how it bends but never told why this happens They were like you will learn this in higher standards

I still can't understand how this bending of light is any different from the gravitational lensing of light by massive objects (like black holes). That's due to gravity curving space time around it and light following the curved path. However, doesn't it hold true in this case too? May be glass being denser than air ( analogous to a galaxy being denser than vacuum), leads the space time around and with in the glass to bend a little bit (way smaller in magnitude though) and as a result we see the light through glass's denser gravity? (Similar to the Eddington's experiment to prove Einstein's theory of general relativity by seeing a star's apparent and not the real position in the sky due to its light bent by sun during a total eclipse. Similar to how we see the position of a coin placed at the bottom of a water jar to be slightly raised due to bent rays? And Einstein definitely used Maxwell's equations in his general relativity. So, couldn't this all be connected and we're understanding refraction wrong all this while? I don't know.

@@richriley5832 😱😱😱

Vivek density and gravity are not the same thing; an extremely dense object will have identical gravitational force as a larger more diffuse object (as long as the mass/energy of the two objects is identical). One way to think of this is if the Earth is compressed to a size of roughly a 1cm diameter. Obviously it is extremely dense at this size, but it’s total mass/energy is the same. The space time curvature at the distance from 1cm Earth to the moon will be identical as the curvature from normal Earth to the moon despite the difference in density. Thus the moons path around 1cm earth will be identical to its current path around the Earth.

AGREED

Me too. I really prefer the long videos, not the short, with deep dives into the subject matter

same

Didn't even realise ten minutes passed.

Maybe mark deep dive videos similarly and only create them according to what interests viewers or creator. Keep the short ones as it keeps the channel alive and more input from viewers. Maybe a weekly deep dive to start?

No need to die. Live long and prosper 🙂.

​@@deanschulze3129exactly 😊

What had you debunked? Fermat's principle is right! Not complet but right!

And are you sure this is the right answer? If you understood it well then tell me why TE polarized light also bends...

He's wrong Concave Earth

@@alephii by TE do you mean transverse electric, any light with a transverse electric field? As in the electric field oscillates orthogonally to the direction of energy transfer? As in any monochromatic light in a homogeneous linear dielectric? I get you're trying to sound smart but you literally just tried to use the video's example as an example that wasn't explained by the video.

@@lachlanbunney6545 still, TE light also bends. The physics can't be different, I am not trying to be smart, just pointing out that if there is a flaw in the explanation then it is probably wrong!

@@lachlanbunney6545 By the way, a transverse electric field in TE doesn't mean that electric field oscillates orthogonal to the wave propagation, because that is obvious in the case you mentioned, but TE refers to the electric field transverse to the incidence plane, the plane that contains the incident and reflected light... The explanation is incomplete and probably wrong, would be much more precise to use the phase continuity in the interface...

The conservation of energy only applies to anything with mass and nothing with mass can travel at the speed of light.

@@scottdc2105 "The conservation of energy only applies to anything with mass": Not true. Conservation of energy always applies . In the case of electromagnetic field (photons), conservation of energy is guaranteed by Poynting theorem: en.wikipedia.org/wiki/Poynting%27s_theorem Also note that my proof doesn't use conservation of energy but conservation of momentum. The conservation of momentum in electromagnetic field is guaranteed by the Maxwell stress tensor : en.wikipedia.org/wiki/Maxwell_stress_tensor

@@SimulatingPhysics But if light has no mass how can photons have mass or momentum? Am i looking at it too simplistically?

@@scottdc2105 A particle without mass can have energy and momentum. The classical formulas (p = m*v , E = 1/2 * m *v^2) are not valid for particles with speed near the speed or light or with the speed of light. Instead we need to use the quantum and relativistic formulas: p = h/λ , E^2 = (p*c)^2 + (m*c^2)^2

@@SimulatingPhysics nice

Yet, there is something wrong with his explanation! It simple don't work for TE polarized waves... So, he is replacing good explanations with a wrong one

He never said there was anything wrong with those principles, he only claimed and demonstrated why they are not the causal explanation of the phenomena.

Woah fuking great comment

I subscribe to that first question. All i can find is math/physics hellish formula stuff.

Yes, when you study differential equations you imagine the whole world is an equation. Preposterous of course.

@@nosuchthing8 Whoooaaa

Yeah 😀

Same here, wondering why the parallel one did not decrease

Because both initial components are actually derived from boundary conditions for M and E part. So this is only valid at entrance point. Further on, the wave propagates straight through that medium and both components are affected by the medium and as long as the medium remains the same, it behaves like perpendicular entrance to that same medium. Otherwise the light would curve in that medium which is not the case.

Apparently the ‘epsolom’ (sorry don’t know spelling) is bigger in glass than in air. This effects the perpendicular component. (I’m not sure myself why this doesn’t affect the parallel component too. Apparently it’s just the perpendicular component 🧐) Because of this, the angle of the perpendicular component is different to that of the parallel component. It is made shorter This creates the angle we see when light his glass.

You didn't miss it. He didn't explain it - he asserted it "from the calculus".

He didn't explain it. 12:22 He showed E field entering perpendicular to the surface, thus the electrons in the glass lined up horizontally to cancel it, so he 'cleverly' deduced that the perpendicular E component got reduced in the glass. If E field entered at an inclination (which should be when light entered at any random angle), then by same logic, electrons in the glass should line up in appropriate direction to cancel it, so both parallel and perpendicular E field components should change.

like our good buddy Einstein said: Everything should be made as simple as possible, but not simpler.

formolzinho a teacher once told me when I asked how long my paper should be his answer was that it should be like a skirt. Long enough to cover the subject yet short enough to still be interesting.

Barely long enough! I'd have liked it to be even more in-depth. Then again, not sure if I'd have clicked on a 40-minute video.

@@TuttleScott Omg, how come I have never heard that one. I love it

anyway I don't understand nothing because in genere physics today are made to don't understand nothing because instead to be something fun and relaxing is contrarity like a very long run of a deer in a forest. everything can be very clear if you want tolearn something but to learn something what is not so precious like a new form of energy bec ause this planet must clean herself from many forms of pollution. I heard light people don't knows what is it.

we need this, please!

Yes!!

yes please!

+1

You might find Coopersmith's _The Lazy Universe_ helpful: www.goodreads.com/book/show/33570590-the-lazy-universe

Haha

The one I remember being taught is the rolling barrel analogy. If you imagine a cylindrical barrel (more like an oil drum) rolling from pavement to grass at an angle, upon striking the grass first, one end will experience drag relative to the other and produce a torque similar to what Mr. Fermilab explained with the "rigid" lines of soldiers. It does replicate the geometry, but like Fermat's principle it provides no explanation as to why photons (which are often considered points or at least spherically symmetrical) would behave like rolling cylinders.

Atleast you guys were taught analogies...😐😐 #fml

In our schools they usually make you memorize the formulas and don't even dare to create some stupid wrong analogy to explain things even for a while

Oh my, this is the worst way to teach anything!

+Lakshya Goel You really arent going to get far in mathematics or physics if you keep asking why questions - the universe works the way it works, be glad it gave you a chance to experience it.

@@NinuRenee lol wtf! The whole point of science is to explain things, curiousity is what leads to discoveries. You are pretty much an animal in forest who doesn't know anything if you just say "it's the way it is, no fucking reasons for it to be" shut the fuck up if you can't understand things, don't demotivate people who actually want to find logic and explaination for physical phenomena....

@@affinix887 Maxwell's equations tell us "how" electricity and magnetism behave, they don't tell us "why" the equations are what they are. Science finds out and describes "how" nature works; it doesn't and cannot tell us "why".

@@rclrd1 That's because the why question is meaningless.

What was the last thing to thru the bugs mind when it the glass windshield? Its rear end. Why? Because he wasnt light enough.

@@no-one-in-particular Finally somebody says it. I felt the same way.

Hi, I found your comment the other day and it seems like the answer I'm looking for but I've been having a hard time getting at what exactly is happening. I think what you're saying is, look at an atom at the top "layer" of glass that's been polarized by the light and turned into a dipole. This dipole will polarize its neighbors. The neighbors on the same layer should apply a force to stretch that dipole out more in the transverse direction, but their forces cancel. The neighbors on the second layer stretch the dipole in the normal direction, and this force cannot be cancelled since there is no layer above the first. This almost seems to work out, but if the transverse forces cancel out and the dipole remains polarizes in the transverse direction, that component of the electric field would also decrease

Fookin Kneelers!

You are the weakest link, kneeeeeeeee'!

Thank you very much for mentioning the book, it helps people who want to get more in depth in the topic.

The cake is a lie

34 years teaching science and marking hsc physics…and you never knew the answer to this question, nor in 34 years try to figure it out on your own in case someone asked?? What else don’t you know and never took the time to learn answers to basic questions?? YikeZzzzzzzz

Yes, I taught Science; geology, chemistry, biology & physics along with mathematics over the 34 years. You are obviously ignorant of a teachers work load to somehow think that you have time to find out & research every nuance of every subject that you teach. There was not a weekend that I was not marking assignments, tests or setting them. Apart from that also engaged in students welfare. Then you have a fool like you make the comment you make! @@AirborneAnt

But can you prove existence and uniqueness of these motives?

Yeah, that has always been a problem for me. I'm fine with learning equations and seeing that it works, but I want to know how it works, otherwise I'm not understanding a god damn thing. 'The sun shines' is not an explanation as to why it emits light. Might as well say god diddit and here's an equation that can calculate the angle when it hits glass.

Talking about radio waves: These can be bent and change polarization in electric fields - think antenna theori. So that should also be possible with light? Is there any examples of bending light or changing polarity shining it between charged plates?

yes please!

in quantic terms is because of Electromagnetically induced transparency

You have to wait... someone is in the back room inventing long math equations. The show will start in fifteen minutes and you will be dazed and confused. A great show !!!

I am waiting the explanation for TE polarized waves before!

A video from Fermilab offering a classical explanation instead of a quantum one. Oh the irony.

after watch 2 videos, i think electric part of light is not enough to properly explain reflection think about it. reflection need parallel and perpendicular part of electric field to flipped 180 degree AND material generated electric field stronger after hit by light to make electric field flipped someone can correct me if im wrong or maybe have better explanation :D

I think reflection is explained by the fact that light is changing magnetic and electric field not just one or the other, the change in electric field gives rise to magentic and visa versa , in the reflection case it the electric field goes to zero as it is completely completely reflective material and hence the change in electric is negative which produces magetic field in the opposite direction which then induces electric field in opposite direction hence reverse the perpendicular component of the field while not affecting the parallel one and effectively reversing the direction of propagation in the perpendicular direction.

@@vik24oct1991 Okay, wow. I have to read this a couple of times. But thanks!

So have experiments been done with varying electric field intensity in glass/water to see if that changes the angle?

I think it's because the beam's vertical electric field is moving against the intrinsic electric field of the material, whereas the beam's horizontal electric field isn't. I'm only guessing though, and I'll defer to anyone who actually knows what they're talking about.

Look to the equations, he showed it

He did not show it. But said that we can get there after some calculus. The so called boundary conditions between two media are shown in em.geosci.xyz/content/maxwell1_fundamentals/interface_conditions/derivation.html It uses the Maxwell equations mentioned in the video, but in its integral form.

@@saspinski That's the math. It doesn't explain the physics. You would think the charges in the material would get polarized by the parallel component. The dielectric constant is also just an approximation, because it assumes the material is continuous.

To fully appreciate this result, you'd need to read the electromagnetic theory. The electromagnetic theory says that light is an electromagnetic wave, it is nothing but oscillating electric and magnetic fields. Electric fields and magnetic fields satisfy a set of 4 equations, 2 for electric fields and 2 for magnetic fields. The 4 equations are different for different media or materials. But at the boundary of two media, both equations of medium 1 and medium 2 must be satisfied, because the boundary belongs to both the media. So the electric field equations in one medium must be equal to the electric field equations in the second medium. This is what we call a boundary "constraint". The electric field is constrained to move in such a way that the boundary conditions or boundary constraints are satisfied. It turns out the boundary constraints you get on solving the equations is that the parallel component of the electric field must not change, and the perpendicular component must decrease. Please not that it is ok if you fully do not understand this, this is something that is taught in undergraduate physics course.

Waves are continuous and superconductor Surface capacitance tensions No gravity Lol just guessing For fun

@@stevesastrohowardkings2245 ?

@@stevesastrohowardkings2245 ??

@@stevesastrohowardkings2245 xDD

What a hard question! I'm delighted that you have asked it. May I say it's all about the supremacy of geometry over physical mater. Any model that includes light waves or rays, and in particular the directions of these waves and rays is wrong by definition. Every such a model is by necessity a 3D structure displayed in an instantaneous space. It doesn't meter if these models were kinetically animated, they are still only the sequences of frozen 3D frames. BTW, the eternity could be the three dimensional only. To be able to answer your question one have to realize that there is no underlying reality of pictorial, i.e. geometrical, models and they should be looked at as if they were eternal objects themselves. However, there is no such thing as the 3D eternal model of light, or of electromagnetic extension in general. Light does have a peculiar direction which is always toward the observing, receipting, point. If you are interested in ... Respect

The equations are linear so the solutions just add up. Look up 'superposition of waves'

You dont need any specific form of boundary condition. It is entirely generic. Check Griffiths.

Thank you.

But his answer is similar to Fermat's principle. But he basically says path integral of everything but the fastest path cancel.

@@joshuascholar3220 Yeah. The multiple solutions mentioned in this video actually *are* physically real, if they don't cancel out with other such solutions. If there's physical structure with details on the same order of magnitude of the wavelength of the light, you get diffraction grating, thanks to all those multiple solutions cancelling out differently. That's why optical disks are rainbow-y. Oily puddles get the same effect from how thin the oil layer is on top of the water. Man that's a good book. I need to read it again.

Holy cow, I just picked this up and I'm super stoked to give it a read.

What page?

@@bradbadley1 You can also watch his lectures, google "feynman new zealand lectures"

Thank you for telling us this.

It is because frequency of oscillating electric field is different for different colors, so you get different values of perpendicular and parallel oscillations, causing that slight change in direction for different colors (hence separating them)

I would just add that the plane of the exit surface of the prism is a factor. Leaving the glass through a surface angled from the entrance surface, the mix of photons that entered, exits on different vectors organized by frequency. With an exit plane parallel to entrance, like a windowpane, they take different angles through, but individually reverse by the same amount on exit, so they all end up back on the same path (as undifferentiated white light).

extend the same theory to different components of light as they have different wavelengths and hence different refraction angles

Because refractive index or the epsilon depends on the wavelength. For different color of light we have different epsilon so the extent of their bending will also be different. That's why they separate from each other!

don't Ruiz everything.