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 <> 

> 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 <> 
> 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
>> This demo tests your understanding of light | Barber pole, part 2
>> Harry

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