Timeline for Grid pattern on a car window when viewed through polarized sunglasses
Current License: CC BY-SA 3.0
15 events
when toggle format | what | by | license | comment | |
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Jun 18, 2023 at 18:22 | vote | accept | Petr | ||
May 30, 2023 at 0:07 | history | protected | CommunityBot | ||
May 29, 2023 at 22:43 | comment | converted from answer | user368488 | I see these spots on other cars and my car. I also bought a new 1976 chevy that had the same spots. | |
Jun 16, 2022 at 11:31 | comment | added | Solomon Slow | Re, "the pattern is much more visible when viewing a reflective surface" That's because the reflected light is polarized. en.wikipedia.org/wiki/Specular_reflection#Polarization You effectively are viewing the car window through a crude polarimeter. The "reflective surface" functions as the polarizer, and your sunglasses function as the analyzer. | |
Aug 18, 2016 at 23:30 | answer | added | Brice | timeline score: 6 | |
Aug 10, 2016 at 1:26 | history | tweeted | twitter.com/StackPhysics/status/763184671257718784 | ||
Aug 9, 2016 at 13:12 | comment | added | Petr | @WetSavannaAnimalakaRodVance +1 to not dying. The picture was taken during a trafic jam when cars were standing still. | |
Aug 9, 2016 at 12:51 | comment | added | Selene Routley | Grand experimental question by the way. I've noticed this many times in my 52 years and now ashamedly realize my inner nerd was never lured by this particular effect I (and I have significant optics training BTW); I guess one's mind is a bit distracted by the aim of not dying in a horrible road accident when driving - I can't otherwise think why I've never thought about this! | |
Aug 9, 2016 at 12:47 | comment | added | Jim | @WetSavannaAnimalakaRodVance Yes, I was kind of hinting that Brewster's angle would play into it that way, but also I was providing the link for further reading on a related phenomenon | |
Aug 9, 2016 at 12:41 | comment | added | Selene Routley | I think what @Jim means is that the light reflected from the surfaces like other car windows and the like becomes partially polarized owing to difference between the reflexion co-efficients for each polarization state (as described by the Fresnel equations) (Jim, hope I'm not misthinking you). The partial polarization then lets you see the effect noted by curiousStudent. I don't know anything about safety glass, so I don't feel I can answer but I'd wager a significant sum on the answer given by curiousStudent in the light of Jim's comment as being the answer, if I were the betting kind. | |
Aug 9, 2016 at 12:15 | comment | added | Jim | for further info, also read up on Brewster's Angle | |
Aug 9, 2016 at 12:13 | comment | added | curiousStudent | From Quora: "These spots are caused during the tempering process. They are intentional stresses which are created in the glass to make it stronger and to control the way it breaks in an accident. The result of this is that it breaks into thousands of small pieces instead of as few large knifelike pieces. The internal stresses can be seen under polarized light or through polarized glasses. The pattern of spots reflects the arrangement of heating elements or flames which are used to apply the heat. " | |
Aug 9, 2016 at 12:10 | comment | added | Petr | @curiousStudent Yes, IIRC the grid appears to be stationary wrt the rear window. | |
Aug 9, 2016 at 12:10 | comment | added | curiousStudent | If you move your head around, does the grid appear to be stationary? | |
Aug 9, 2016 at 12:06 | history | asked | Petr | CC BY-SA 3.0 |