One other thing. If you aim a laser into the inside of a transparent tube, you get that barber pole effect spiraling around at a greater or lesser frequency depending on the angle of the beam into the interior of the tube. So that may explain the barber pole in the video.
------- Original Message ------- On Thursday, September 21st, 2023 at 9:05 PM, MSF <foster...@protonmail.com> wrote: > I can't even begin to express how conceptually and experimentally wrong this > demonstration is. The first thing is the perpetuation of the mistaken idea > that photons are wiggling in a sinusiodal fashion. When you see that sine > wave, it's a graph of the varying field as the wave propagates. It's not the > wave itself. This is such a common miscommunication that physics students > often have a hard time getting over it. > > Just for the sake of context, this guy should have at least mentioned the > practical application of this phenomenon, which is the polarizing > saccharimeter. Wine makers, for example, use this device to measure the > amount of dextrose (glucose) in grape juice so they can harvest the grapes at > their peak. So next time you're enjoying that glass of wine, think, > "Mmm...saccharimeter." > > The experimental setup in this demonstration has, in my opinion, a fatal > flaw. The light source seems to be too broad to test the phenomenon. > Furthermore it appears to be tilted at an angle at the entrance to the tube. > Both of these factors will have the light glancing off the interior of the > tube. At least some of the light will be at Brewster's angle for the > interface between the sugar solution and the tube. So the interior of the > tube becomes its own polarizer. > > Another thing that should have been mentioned is that the light, while > circularly polarized in the sugar solution, emerges linearly polarized. Maybe > that's obvious, but it should have been stated. > Having said all that, it's a hell of a beautiful demonstration. It should be > repeated with a narrow beam of light just to see the results. > > ------- Original Message ------- > On Sunday, September 10th, 2023 at 1:15 AM, H L V <hveeder...@gmail.com> > wrote: > >> The well known mathematics youtuber 3Blue1Brown recently published two >> interesting videos on polarized light passing through a clear glass tube >> filled with dissolved sugar in water. (He is working on a third video.) >> Normally he explains mathematical concepts with nicely rendered visual >> explanations so the inclusion of a physical demo is something new for his >> channel. The mathematical explanation offered in part 2 seems to >> qualitatively account for what is observed in part 1 but there is a lively >> discussion in the comment section on part 2 where it is pointed out that his >> explanation makes a prediction that he acknowledges is not actually >> observed. I enjoy it when textbook science bumps up against reality! It will >> be interesting to see if he can account for this theoretical weakness in his >> third video. >> >> This demo tests your understanding of light | Barber pole, part 1 >> https://www.youtube.com/watch?v=QCX62YJCmGk >> >> This demo tests your understanding of light | Barber pole, part 2 >> https://www.youtube.com/watch?v=aXRTczANuIs&t=0s >> >> Harry
