{"id":1620,"date":"2020-12-18T12:15:27","date_gmt":"2020-12-18T06:45:27","guid":{"rendered":"https:\/\/cbselibrary.com\/?p=1620"},"modified":"2020-12-18T15:22:43","modified_gmt":"2020-12-18T09:52:43","slug":"atmospheric-refraction","status":"publish","type":"post","link":"https:\/\/cbselibrary.com\/atmospheric-refraction\/","title":{"rendered":"What is meant by Atmospheric Refraction?"},"content":{"rendered":"<h2><strong>What is meant by Atmospheric\u00a0<a href=\"https:\/\/cbselibrary.com\/refraction-of-light\/\">Refraction<\/a>?<\/strong><\/h2>\n<p>We can observe the apparent random wavering or flickering of objects seen through a turbulent stream of hot air rising above a fire or a radiator. The air just above the fire becomes hotter than the air further up. The hotter air is lighter (less dense) than the cooler air above it, and has a refractive index slightly less than that of the cooler air. Since the physical conditions of the refracting medium (air) are not stationary, the apparent position of the object, as seen through the hot air, fluctuates. This wavering is thus an effect of atmospheric refraction (refraction of light by the earth\u2019s atmosphere) on a small scale in our local environment. The twinkling of stars is a similar phenomenon on a much larger scale.<\/p>\n<p><strong>People also ask<\/strong><\/p>\n<ul>\n<li><a href=\"https:\/\/cbselibrary.com\/natural-phenomenon-due-refraction-light\/\">Examples of refraction of light<\/a><\/li>\n<li><a href=\"https:\/\/cbselibrary.com\/analysing-refraction-waves\/\">Analysing Refraction of Waves<\/a><\/li>\n<li><a href=\"https:\/\/cbselibrary.com\/measure-refractive-index\/\">What is the index of refraction?<\/a><\/li>\n<li><a href=\"https:\/\/cbselibrary.com\/refraction-of-light-through-glass-slab\/\">Refraction of light through\u00a0glass slab<\/a><\/li>\n<\/ul>\n<h3>Why do stars twinkle and planets do not?<\/h3>\n<p>The twinkling of a star is due to atmospheric refraction of starlight. The starlight, on entering the earth\u2019s atmosphere, undergoes refraction continuously before it reaches the earth. The atmospheric refraction occurs in a medium of gradually changing refractive index.<br \/>\nSince the stars are very distant, they approximate point-sized sources of light. As the path of rays of light coming from the star goes on varying slightly, the apparent position of the star fluctuates and the amount of starlight entering the eye flickers \u2013 the star sometimes appears brighter, and at some other time, fainter, which is the twinkling effect.<br \/>\n<img loading=\"lazy\" class=\"size-full wp-image-134473 aligncenter\" src=\"https:\/\/cbselibrary.com\/wp-content\/uploads\/2018\/09\/What-is-meant-by-Atmospheric-Refraction-1.png\" alt=\"What is meant by Atmospheric Refraction 1\" width=\"284\" height=\"267\" \/><\/p>\n<h3><strong>Why don\u2019t the planets twinkle?<\/strong><\/h3>\n<p>The planets are much closer to the earth, and are thus seen as extended sources. If we consider a planet as a collection of a large number of point-sized sources of light, the total variation in the amount of light entering our eye from all the individual point-sized sources will average out to zero, thereby nullifying the twinkling effect.<\/p>\n<h3>What is the reason for Advanced sunrise and delayed sunset?<\/h3>\n<p><strong><img loading=\"lazy\" class=\"size-full wp-image-134475 aligncenter\" src=\"https:\/\/cbselibrary.com\/wp-content\/uploads\/2018\/09\/What-is-meant-by-Atmospheric-Refraction-2.png\" alt=\"What is meant by Atmospheric Refraction 2\" width=\"467\" height=\"330\" srcset=\"https:\/\/cbselibrary.com\/wp-content\/uploads\/2018\/09\/What-is-meant-by-Atmospheric-Refraction-2.png 467w, https:\/\/cbselibrary.com\/wp-content\/uploads\/2018\/09\/What-is-meant-by-Atmospheric-Refraction-2-300x212.png 300w\" sizes=\"(max-width: 467px) 100vw, 467px\" \/>Fig. <\/strong>Atmospheric refraction at sunrise and sunset<br \/>\nAdvance sunrise and delayed sunset The Sun is visible to us about 2 minutes before the actual sunrise, and about 2 minutes after the actual sunset because of atmospheric refraction. By actual sunrise, we mean the actual crossing of the horizon by the Sun. figure shows the actual and apparent positions of the Sun with respect to the horizon. The time difference between actual sunset and the apparent sunset is about 2 minutes. The apparent flattening of the Sun\u2019s disc at sunrise and sunset is also due to the same phenomenon.<\/p>\n","protected":false},"excerpt":{"rendered":"<p>What is meant by Atmospheric\u00a0Refraction? We can observe the apparent random wavering or flickering of objects seen through a turbulent stream of hot air rising above a fire or a radiator. The air just above the fire becomes hotter than the air further up. The hotter air is lighter (less dense) than the cooler air &#8230; <a title=\"What is meant by Atmospheric Refraction?\" class=\"read-more\" href=\"https:\/\/cbselibrary.com\/atmospheric-refraction\/\" aria-label=\"More on What is meant by Atmospheric Refraction?\">Read more<\/a><\/p>\n","protected":false},"author":3,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"spay_email":""},"categories":[404],"tags":[510,511,477,512,513],"yoast_head":"<!-- This site is optimized with the Yoast SEO Premium plugin v17.8 (Yoast SEO v18.4.1) - https:\/\/yoast.com\/wordpress\/plugins\/seo\/ -->\n<title>What is meant by Atmospheric Refraction? - CBSE Library<\/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:\/\/cbselibrary.com\/atmospheric-refraction\/\" \/>\n<meta property=\"og:locale\" content=\"en_US\" \/>\n<meta property=\"og:type\" content=\"article\" \/>\n<meta property=\"og:title\" content=\"What is meant by Atmospheric Refraction?\" \/>\n<meta property=\"og:description\" content=\"What is meant by Atmospheric\u00a0Refraction? We can observe the apparent random wavering or flickering of objects seen through a turbulent stream of hot air rising above a fire or a radiator. The air just above the fire becomes hotter than the air further up. The hotter air is lighter (less dense) than the cooler air ... 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We can observe the apparent random wavering or flickering of objects seen through a turbulent stream of hot air rising above a fire or a radiator. The air just above the fire becomes hotter than the air further up. The hotter air is lighter (less dense) than the cooler air ... 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