[{"id":342,"title":"The simple observation by Huygens that disproved Newton's rule for the extraordinary refraction of calcite","sha":"5f4062653c5b39d0373518e556653052","user_id":null,"state":"published","body":"Huygens (1629\u0026#8211;1695), in his \u003ca href=\"http://www.gutenberg.org/files/14725/14725-h/14725-h.htm\"\u003e\u003ci\u003eTreatise on Light\u003c/i\u003e\u003c/a\u003e (1690), explained the double refraction of calcite on the correct hypothesis that the secondary waves for the \u0026ldquo;extraordinary\u0026rdquo; refraction are \u003cem\u003espheroidal\u003c/em\u003e rather than spherical. His theory explained, \u003ci\u003einter alia\u003c/i\u003e, his simple observation that when a calcite crystal is placed on a horizontal page of text, the ordinary image appears higher than the extraordinary image (Ch.V, \u003ca href=\"http://www.gutenberg.org/files/14725/14725-h/14725-h.htm#Page_81\"\u003eArt.\u0026#8239;39)\u003c/a\u003e.\r\n\r\nNewton, in Qu.\u0026#8239;17 of the Latin edition of his \u003ci\u003eOpticks\u003c/i\u003e (1706), or Qu.\u0026#8239;25 (in \u003ca href=\"http://www.newtonproject.sussex.ac.uk/view/texts/diplomatic/NATP00051\"\u003eBk.\u0026#8239;3\u003c/a\u003e) of later English editions, gave his own \u0026lsquo;rule\u0026rsquo; for double refraction. Let a ray from an external point \u003ci\u003eL\u003c/i\u003e strike one face of a calcite crystal at point \u003ci\u003eP\u003c/i\u003e, and be refracted to point \u003ci\u003eO\u003c/i\u003e on the opposite face by the \u003ci\u003eO\u003c/i\u003erdinary refraction, and to point \u003ci\u003eE\u003c/i\u003e on the opposite face by the \u003ci\u003eE\u003c/i\u003extraordinary refraction. According to Newton's rule, the displacement vector \u003ci\u003eOE\u003c/i\u003e does not vary with the direction of the incident ray.\r\n\r\nIt is \u003ca href=\"http://www.grputland.com/2016/10/observation-by-huygens-that-should-have-discredited-newtons-rule.html\"\u003eeasily shown\u003c/a\u003e that if this rule were true, the two text images reported by Huygens would have been at the same height.\r\n\r\nNewton's rule was disproven in 1788. That it had already been disproven by a single qualitative observation, before it was published, seems to have escaped notice.","created_at":"2016-10-24T11:12:09.235Z","updated_at":"2016-10-25T06:00:38.030Z","zenodo_id":162990,"doi":"https://doi.org/10.5281/zenodo.162990","subject":null,"tags":["optics","history","newton","huygens","birefringence"],"vote_count":0,"view_count":1,"score":0.1,"deleted":false,"muted":false,"tweeted":true,"attachment_file_name":null,"attachment_content_type":null,"attachment_file_size":null,"attachment_updated_at":null},{"id":915,"title":"Body Image Compensation","sha":"af7c64934f0fc8398de4228c87db23dd","user_id":null,"state":"published","body":"I here describe a solution to a problem in the area of optics. Worldwide, there is concern over the effects of the use of smartphones, tablets, computers, and webcams on body image. The use of cameras in these devices reinforces a [thin ideal](https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7552652/), which is damaging in its effects. I identify the major cause of the problem as camera hardware. A single lens may increase facial thinness in an image by 10%, compared with a face seen with two human eyes. This is due to [angular size](https://www.austincc.edu/jheath/Solar/Hand/Angsize/angsiz.htm), or how wide an object appears to be. See the Attachment Figure 1, a smartphone photo of US politician Alexandria Ocasio-Cortez. Such thinness is overcome by mounting two lenses about 6 cm apart, where the average human [pupillary distance](https://www.allaboutvision.com/eye-care/measure-pupillary-distance/) is 63 mm. An (inter alia) smartphone would then include software to integrate the two images. The Attachment Figures 2 and 3 show my own face at about 25 cm distance from a Lenovo laptop camera (314 pixels ear to ear). Attachment Figure 4 shows these images integrated (338 pixels ear to ear), as if viewed with human eyes. This broadens my face about 7.6% Currently, popular [smartphone](https://www.techadvisor.com/feature/mobile-phone/best-camera-phone-3675843/) and [computer](https://www.xda-developers.com/best-laptops-1080p-webcam/) cameras do not have such a feature. Companies which adopt this technology could boast of Body Image Compensation.","created_at":"2022-02-23T20:27:07.405Z","updated_at":"2022-02-26T06:00:44.379Z","zenodo_id":6288634,"doi":"https://doi.org/10.5281/zenodo.6288634","subject":null,"tags":["thinness ideal","social media","smartphone","tablet","computer","webcam","optics"],"vote_count":0,"view_count":1,"score":0.1,"deleted":false,"muted":false,"tweeted":true,"attachment_file_name":"Facial_Thinness.jpg","attachment_content_type":"image/jpeg","attachment_file_size":212099,"attachment_updated_at":"2022-02-23T20:27:07.314Z"}]