{"id":621837,"date":"2026-01-18T21:05:47","date_gmt":"2026-01-18T20:05:47","guid":{"rendered":"https:\/\/cronologia-universale.it\/1901-6\/"},"modified":"2026-01-18T21:05:47","modified_gmt":"2026-01-18T20:05:47","slug":"1887-4","status":"publish","type":"post","link":"https:\/\/cronologia-universale.it\/en\/1887-4\/","title":{"rendered":"1887"},"content":{"rendered":"<p>Heinrich Hertz discovered a puzzling phenomenon (for physicists): the photoelectric effect. Ultraviolet (UV) light on a charged metal surface causes sparks (loses electrons), while infrared (IR) light does not. Wave theory at the time predicted that energy is proportional to amplitude, not frequency. It would take Albert Einstein to uncover the flaw.<\/p>\n","protected":false},"excerpt":{"rendered":"<p>Heinrich Hertz discovered a puzzling phenomenon (for physicists): the photoelectric effect. Ultraviolet (UV) light on&#8230;<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"_acf_changed":false,"footnotes":""},"categories":[41],"tags":[],"class_list":["post-621837","post","type-post","status-publish","format-standard","hentry","category-s-en"],"acf":[],"yoast_head":"<!-- This site is optimized with the Yoast SEO plugin v26.0 - https:\/\/yoast.com\/wordpress\/plugins\/seo\/ -->\n<title>1887 - Cronologia Universale<\/title>\n<meta name=\"robots\" content=\"index, follow, max-snippet:-1, max-image-preview:large, max-video-preview:-1\" \/>\n<link rel=\"canonical\" href=\"https:\/\/cronologia-universale.it\/en\/1887-4\/\" \/>\n<meta property=\"og:locale\" content=\"en_US\" \/>\n<meta property=\"og:type\" content=\"article\" \/>\n<meta property=\"og:title\" content=\"1887 - Cronologia Universale\" \/>\n<meta property=\"og:description\" content=\"Heinrich Hertz discovered a puzzling phenomenon (for physicists): the photoelectric effect. 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