{"id":91128,"date":"2025-06-01T10:47:26","date_gmt":"2025-06-01T10:47:26","guid":{"rendered":"https:\/\/exam.pscnotes.com\/mcq\/?p=91128"},"modified":"2025-06-01T10:47:26","modified_gmt":"2025-06-01T10:47:26","slug":"consider-the-following-phenomena-1-size-of-the-sun-at-dusk-2-co","status":"publish","type":"post","link":"https:\/\/exam.pscnotes.com\/mcq\/consider-the-following-phenomena-1-size-of-the-sun-at-dusk-2-co\/","title":{"rendered":"Consider the following phenomena :\n  1. Size of the sun at dusk  2. Co"},"content":{"rendered":"<p>Consider the following phenomena :<\/p>\n<ul>\n<li>1. Size of the sun at dusk<\/li>\n<li>2. Colour of the sun at dawn<\/li>\n<li>3. Moon being visible at dawn<\/li>\n<li>4. Twinkle of stars in the sky<\/li>\n<li>5. Polestar being visible in the sky<\/li>\n<\/ul>\n<p>Which of the above are optical illusions?<\/p>\n<p>[amp_mcq option1=&#8221;1, 2 and 3&#8243; option2=&#8221;3, 4 and 5&#8243; option3=&#8221;1, 2 and 4&#8243; option4=&#8221;2, 3 and 5&#8243; correct=&#8221;option3&#8243;]<\/p>\n<div class=\"psc-box-pyq-exam-year-detail\">\n<div class=\"pyq-exam\">\n<div class=\"psc-heading\">This question was previously asked in<\/div>\n<div class=\"psc-title line-ellipsis\">UPSC IAS &#8211; 2013<\/div>\n<\/div>\n<div class=\"pyq-exam-psc-buttons\"><a href=\"\/pyq\/pyq-upsc-ias-2013.pdf\" target=\"_blank\" class=\"psc-pdf-button\" rel=\"noopener\">Download PDF<\/a><a href=\"\/pyq-upsc-ias-2013\" target=\"_blank\" class=\"psc-attempt-button\" rel=\"noopener\">Attempt Online<\/a><\/div>\n<\/div>\n<section id=\"pyq-correct-answer\">The size of the sun at dusk, the colour of the sun at dawn, and the twinkle of stars in the sky are considered optical phenomena or illusions.<\/section>\n<section id=\"pyq-key-points\">1. The apparent increase in the size of the sun (or moon) near the horizon (dusk) is an optical illusion known as the Moon illusion. 2. The reddish\/orange colour of the sun at dawn is due to atmospheric scattering (Rayleigh scattering), where shorter wavelengths (blue\/green) are scattered away more than longer wavelengths (red\/orange) when light travels a longer path through the atmosphere. This phenomenon leads to a perceived colour change. 4. The twinkling of stars is caused by atmospheric refraction due to turbulence in the air, which makes the light from distant stars appear to fluctuate in brightness and position.<\/section>\n<section id=\"pyq-additional-information\">Phenomena 3 (Moon being visible at dawn) and 5 (Polestar being visible in the sky) are real astronomical occurrences related to the celestial positions of these bodies and are not optical illusions in the sense of being perceptual distortions or atmospheric effects causing altered appearance. Therefore, 1, 2, and 4 fit the description of optical illusions or related atmospheric optical phenomena causing altered visual perception.<\/section>\n","protected":false},"excerpt":{"rendered":"<p>Consider the following phenomena : 1. Size of the sun at dusk 2. Colour of the sun at dawn 3. Moon being visible at dawn 4. Twinkle of stars in the sky 5. Polestar being visible in the sky Which of the above are optical illusions? [amp_mcq option1=&#8221;1, 2 and 3&#8243; option2=&#8221;3, 4 and 5&#8243; &#8230; <\/p>\n<p class=\"read-more-container\"><a title=\"Consider the following phenomena :\n  1. Size of the sun at dusk  2. Co\" class=\"read-more button\" href=\"https:\/\/exam.pscnotes.com\/mcq\/consider-the-following-phenomena-1-size-of-the-sun-at-dusk-2-co\/#more-91128\">Detailed Solution<span class=\"screen-reader-text\">Consider the following phenomena :<br \/>\n  1. Size of the sun at dusk  2. Co<\/span><\/a><\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"closed","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[1092],"tags":[1467,1153,1128],"class_list":["post-91128","post","type-post","status-publish","format-standard","hentry","category-upsc-ias","tag-1467","tag-optics","tag-physics","no-featured-image-padding"],"yoast_head":"<!-- This site is optimized with the Yoast SEO Premium plugin v22.2 (Yoast SEO v23.3) - https:\/\/yoast.com\/wordpress\/plugins\/seo\/ -->\n<title>Consider the following phenomena :  1. Size of the sun at dusk 2. Co<\/title>\n<meta name=\"description\" content=\"The size of the sun at dusk, the colour of the sun at dawn, and the twinkle of stars in the sky are considered optical phenomena or illusions. 1. The apparent increase in the size of the sun (or moon) near the horizon (dusk) is an optical illusion known as the Moon illusion. 2. The reddish\/orange colour of the sun at dawn is due to atmospheric scattering (Rayleigh scattering), where shorter wavelengths (blue\/green) are scattered away more than longer wavelengths (red\/orange) when light travels a longer path through the atmosphere. This phenomenon leads to a perceived colour change. 4. The twinkling of stars is caused by atmospheric refraction due to turbulence in the air, which makes the light from distant stars appear to fluctuate in brightness and position.\" \/>\n<meta name=\"robots\" content=\"index, follow, max-snippet:-1, max-image-preview:large, max-video-preview:-1\" \/>\n<link rel=\"canonical\" href=\"https:\/\/exam.pscnotes.com\/mcq\/consider-the-following-phenomena-1-size-of-the-sun-at-dusk-2-co\/\" \/>\n<meta property=\"og:locale\" content=\"en_US\" \/>\n<meta property=\"og:type\" content=\"article\" \/>\n<meta property=\"og:title\" content=\"Consider the following phenomena :  1. Size of the sun at dusk 2. 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The twinkling of stars is caused by atmospheric refraction due to turbulence in the air, which makes the light from distant stars appear to fluctuate in brightness and position.\" \/>\n<meta property=\"og:url\" content=\"https:\/\/exam.pscnotes.com\/mcq\/consider-the-following-phenomena-1-size-of-the-sun-at-dusk-2-co\/\" \/>\n<meta property=\"og:site_name\" content=\"MCQ and Quiz for Exams\" \/>\n<meta property=\"article:published_time\" content=\"2025-06-01T10:47:26+00:00\" \/>\n<meta name=\"author\" content=\"rawan239\" \/>\n<meta name=\"twitter:card\" content=\"summary_large_image\" \/>\n<meta name=\"twitter:label1\" content=\"Written by\" \/>\n\t<meta name=\"twitter:data1\" content=\"rawan239\" \/>\n\t<meta name=\"twitter:label2\" content=\"Est. reading time\" \/>\n\t<meta name=\"twitter:data2\" content=\"1 minute\" \/>\n<!-- \/ Yoast SEO Premium plugin. -->","yoast_head_json":{"title":"Consider the following phenomena :  1. Size of the sun at dusk 2. Co","description":"The size of the sun at dusk, the colour of the sun at dawn, and the twinkle of stars in the sky are considered optical phenomena or illusions. 1. The apparent increase in the size of the sun (or moon) near the horizon (dusk) is an optical illusion known as the Moon illusion. 2. The reddish\/orange colour of the sun at dawn is due to atmospheric scattering (Rayleigh scattering), where shorter wavelengths (blue\/green) are scattered away more than longer wavelengths (red\/orange) when light travels a longer path through the atmosphere. This phenomenon leads to a perceived colour change. 4. The twinkling of stars is caused by atmospheric refraction due to turbulence in the air, which makes the light from distant stars appear to fluctuate in brightness and position.","robots":{"index":"index","follow":"follow","max-snippet":"max-snippet:-1","max-image-preview":"max-image-preview:large","max-video-preview":"max-video-preview:-1"},"canonical":"https:\/\/exam.pscnotes.com\/mcq\/consider-the-following-phenomena-1-size-of-the-sun-at-dusk-2-co\/","og_locale":"en_US","og_type":"article","og_title":"Consider the following phenomena :  1. Size of the sun at dusk 2. Co","og_description":"The size of the sun at dusk, the colour of the sun at dawn, and the twinkle of stars in the sky are considered optical phenomena or illusions. 1. The apparent increase in the size of the sun (or moon) near the horizon (dusk) is an optical illusion known as the Moon illusion. 2. The reddish\/orange colour of the sun at dawn is due to atmospheric scattering (Rayleigh scattering), where shorter wavelengths (blue\/green) are scattered away more than longer wavelengths (red\/orange) when light travels a longer path through the atmosphere. This phenomenon leads to a perceived colour change. 4. The twinkling of stars is caused by atmospheric refraction due to turbulence in the air, which makes the light from distant stars appear to fluctuate in brightness and position.","og_url":"https:\/\/exam.pscnotes.com\/mcq\/consider-the-following-phenomena-1-size-of-the-sun-at-dusk-2-co\/","og_site_name":"MCQ and Quiz for Exams","article_published_time":"2025-06-01T10:47:26+00:00","author":"rawan239","twitter_card":"summary_large_image","twitter_misc":{"Written by":"rawan239","Est. reading time":"1 minute"},"schema":{"@context":"https:\/\/schema.org","@graph":[{"@type":"WebPage","@id":"https:\/\/exam.pscnotes.com\/mcq\/consider-the-following-phenomena-1-size-of-the-sun-at-dusk-2-co\/","url":"https:\/\/exam.pscnotes.com\/mcq\/consider-the-following-phenomena-1-size-of-the-sun-at-dusk-2-co\/","name":"Consider the following phenomena : 1. Size of the sun at dusk 2. 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The twinkling of stars is caused by atmospheric refraction due to turbulence in the air, which makes the light from distant stars appear to fluctuate in brightness and position.","breadcrumb":{"@id":"https:\/\/exam.pscnotes.com\/mcq\/consider-the-following-phenomena-1-size-of-the-sun-at-dusk-2-co\/#breadcrumb"},"inLanguage":"en-US","potentialAction":[{"@type":"ReadAction","target":["https:\/\/exam.pscnotes.com\/mcq\/consider-the-following-phenomena-1-size-of-the-sun-at-dusk-2-co\/"]}]},{"@type":"BreadcrumbList","@id":"https:\/\/exam.pscnotes.com\/mcq\/consider-the-following-phenomena-1-size-of-the-sun-at-dusk-2-co\/#breadcrumb","itemListElement":[{"@type":"ListItem","position":1,"name":"Home","item":"https:\/\/exam.pscnotes.com\/mcq\/"},{"@type":"ListItem","position":2,"name":"UPSC IAS","item":"https:\/\/exam.pscnotes.com\/mcq\/category\/upsc-ias\/"},{"@type":"ListItem","position":3,"name":"Consider the following phenomena : 1. Size of the sun at dusk 2. 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