{"id":88563,"date":"2025-06-01T07:14:54","date_gmt":"2025-06-01T07:14:54","guid":{"rendered":"https:\/\/exam.pscnotes.com\/mcq\/?p=88563"},"modified":"2025-06-01T07:14:54","modified_gmt":"2025-06-01T07:14:54","slug":"light-rays-move-in-straight-lines-but-through-an-optical-fibre-they","status":"publish","type":"post","link":"https:\/\/exam.pscnotes.com\/mcq\/light-rays-move-in-straight-lines-but-through-an-optical-fibre-they\/","title":{"rendered":"Light rays move in straight lines. But through an optical fibre, they"},"content":{"rendered":"

Light rays move in straight lines. But through an optical fibre, they can move in any type of zigzag path because<\/p>\n

[amp_mcq option1=”the holes through the fibre are extremely fine.” option2=”light rays are absorbed at the entry end and relieved at the exit end of the fibre.” option3=”scattering of light occurs inside the fibre.” option4=”successive total internal reflections occur as a ray moves through the fibre.” correct=”option4″]<\/p>\n

\n
\n
This question was previously asked in<\/div>\n
UPSC NDA-2 – 2019<\/div>\n<\/div>\n
Download PDF<\/a>Attempt Online<\/a><\/div>\n<\/div>\n
\nThe correct answer is D) successive total internal reflections occur as a ray moves through the fibre.
\n<\/section>\n
\nOptical fibres work on the principle of Total Internal Reflection (TIR). The fibre consists of a core with a higher refractive index surrounded by cladding with a lower refractive index. Light entering the core at suitable angles strikes the core-cladding interface at angles greater than the critical angle, causing the light to be reflected back into the core. This process repeats along the length of the fibre, guiding the light even if the fibre is bent.
\n<\/section>\n
\nOption A is irrelevant to the principle of light propagation. Option B is incorrect; light is transmitted, not absorbed and re-emitted in this way. Option C, scattering, generally leads to loss of signal, not efficient transmission through zigzag paths. TIR is the key phenomenon enabling light transmission through optical fibres over long distances with minimal loss.
\n<\/section>\n","protected":false},"excerpt":{"rendered":"

Light rays move in straight lines. But through an optical fibre, they can move in any type of zigzag path because [amp_mcq option1=”the holes through the fibre are extremely fine.” option2=”light rays are absorbed at the entry end and relieved at the exit end of the fibre.” option3=”scattering of light occurs inside the fibre.” option4=”successive … <\/p>\n

Detailed SolutionLight rays move in straight lines. But through an optical fibre, they<\/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":[1094],"tags":[1119,1153,1128],"class_list":["post-88563","post","type-post","status-publish","format-standard","hentry","category-upsc-nda-2","tag-1119","tag-optics","tag-physics","no-featured-image-padding"],"yoast_head":"\nLight rays move in straight lines. But through an optical fibre, they<\/title>\n<meta name=\"description\" content=\"The correct answer is D) successive total internal reflections occur as a ray moves through the fibre. Optical fibres work on the principle of Total Internal Reflection (TIR). The fibre consists of a core with a higher refractive index surrounded by cladding with a lower refractive index. Light entering the core at suitable angles strikes the core-cladding interface at angles greater than the critical angle, causing the light to be reflected back into the core. This process repeats along the length of the fibre, guiding the light even if the fibre is bent.\" \/>\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\/light-rays-move-in-straight-lines-but-through-an-optical-fibre-they\/\" \/>\n<meta property=\"og:locale\" content=\"en_US\" \/>\n<meta property=\"og:type\" content=\"article\" \/>\n<meta property=\"og:title\" content=\"Light rays move in straight lines. But through an optical fibre, they\" \/>\n<meta property=\"og:description\" content=\"The correct answer is D) successive total internal reflections occur as a ray moves through the fibre. Optical fibres work on the principle of Total Internal Reflection (TIR). The fibre consists of a core with a higher refractive index surrounded by cladding with a lower refractive index. Light entering the core at suitable angles strikes the core-cladding interface at angles greater than the critical angle, causing the light to be reflected back into the core. 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