File:PositronDiscovery.jpg

預覽大細：608 × 599 像素。第啲解像度：243 × 240 像素｜487 × 480 像素｜779 × 768 像素｜1,039 × 1,024 像素｜2,408 × 2,374 像素。

原本檔案 ‎（2,408 × 2,374 像素，檔案大細：1.91 MB ，MIME類型：image/jpeg）

呢個檔案係出自維基同享。下面係佢喺嗰邊嘅描述。
Commons 收集自由嘅媒體檔案。你可以去幫手。

摘要

描述PositronDiscovery.jpg	English: Cloud chamber photograph of the first positron ever observed. The thick horizontal line is a lead plate. The positron entered the cloud chamber in the lower left, was slowed down by the lead plane, and curved to the upper left. The curvature of the path is caused by an applied magnetic field that acts perpendicular to the image plane. The higher energy of the entering positron resulted in lower curvature of its path. Original caption: A 63 million volt positron (H_ρ = 2.1×10⁵ gauss-cm) passing through a 6 mm lead plate and emerging as a 23 million volt positron (H_ρ = 7.5×10⁴ gauss-cm). The length of this latter path is at least ten times greater than the possible length of a proton path of this curvature.
日期	Photographed 1932年8月2號. Published 1933年3月15號.
來源	Anderson, Carl D. (1933). "The Positive Electron". Physical Review 43 (6): 491–494. DOI:10.1103/PhysRev.43.491.
作者	Carl D. Anderson (1905–1991)
許可 (重用呢個檔案)	Obtained from American Physical Society, March 5, 2008. The copyright for the periodical containing this picture, if renewed, would have had to be renewed in 1960 or 1961. I checked the Catalog of copyright entries for Periodicals in 1960 and 1961, http://onlinebooks.library.upenn.edu/cce/, but The Physical Review is not listed there. Therefore, the copyright on the entire issue of The Physical Review, including this picture, has expired.

協議

This work is in the public domain because it was published in the United States between 1929 and 1963, and although there may or may not have been a copyright notice, the copyright was not renewed. For further explanation, see Commons:Hirtle chart and the copyright renewal logs. Note that it may still be copyrighted in jurisdictions that do not apply the rule of the shorter term for US works (depending on the date of the author's death), such as Canada (70 years p.m.a.), Mainland China (50 years p.m.a., not Hong Kong or Macao), Germany (70 years p.m.a.), Mexico (100 years p.m.a.), Switzerland (70 years p.m.a.), and other countries with individual treaties.

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	日期／時間	尺寸	用戶	註解
現時	2013年5月6號 (一) 19:12	2,408 × 2,374（1.91 MB）	Quibik	Combined with a moire- and halftone-free but blurrier version that was also provided in the article. Much more accurate now.
	2013年5月6號 (一) 18:10	2,500 × 2,500（1.97 MB）	Quibik	Re-extracted the image from the source article in greater resolution, removed halftone & moiré and adjusted levels.
	2008年5月3號 (六) 16:54	848 × 755（71 KB）	HPaul	{{Information \|Description=Cloud chamber photograph of the first positron ever observed \|Source=Physical Review, Vol.43, p. 491 \|Date=March 15, 1933 \|Author=Carl D. Anderson \|Permission=obtained from American Physical Society, March 5, 2008 \|other_version