{"id":89089,"date":"2025-06-01T07:29:09","date_gmt":"2025-06-01T07:29:09","guid":{"rendered":"https:\/\/exam.pscnotes.com\/mcq\/?p=89089"},"modified":"2025-06-01T07:29:09","modified_gmt":"2025-06-01T07:29:09","slug":"which-one-among-the-following-is-the-correct-focal-length-of-a-combina","status":"publish","type":"post","link":"https:\/\/exam.pscnotes.com\/mcq\/which-one-among-the-following-is-the-correct-focal-length-of-a-combina\/","title":{"rendered":"Which one among the following is the correct focal length of a combina"},"content":{"rendered":"

Which one among the following is the correct focal length of a combination of lenses of power 2\u00b75 D and \u20132\u00b70 D ?<\/p>\n

[amp_mcq option1=”+0\u00b75 m” option2=”\u20130\u00b75 m” option3=”+2\u00b70 m” option4=”\u20132\u00b70 m” correct=”option3″]<\/p>\n

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This question was previously asked in<\/div>\n
UPSC NDA-2 – 2024<\/div>\n<\/div>\n
Download PDF<\/a>Attempt Online<\/a><\/div>\n<\/div>\n
\nFor thin lenses in contact, the total power of the combination (P_total) is the algebraic sum of the individual powers (P\u2081, P\u2082). Given P\u2081 = 2.5 D and P\u2082 = -2.0 D, the total power is P_total = P\u2081 + P\u2082 = 2.5 D + (-2.0 D) = 0.5 D. The focal length (f) of a lens or lens combination is the reciprocal of its power (P), with power in dioptres (D) and focal length in meters (m). So, f_total = 1 \/ P_total = 1 \/ 0.5 D = 1 \/ (0.5 m\u207b\u00b9) = 2 m. The focal length is positive, indicating a converging lens combination.
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\nPower of a lens (P) is the reciprocal of its focal length (f) in meters (P = 1\/f). The power of a combination of thin lenses in contact is the sum of their individual powers. Positive power indicates a converging lens, and negative power indicates a diverging lens.
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\nThe unit of power is the dioptre (D), which is equal to m\u207b\u00b9. A combination of a converging lens (+P) and a diverging lens (-P’) can result in a net converging or diverging combination depending on the relative magnitudes of their powers.
\n<\/section>\n","protected":false},"excerpt":{"rendered":"

Which one among the following is the correct focal length of a combination of lenses of power 2\u00b75 D and \u20132\u00b70 D ? [amp_mcq option1=”+0\u00b75 m” option2=”\u20130\u00b75 m” option3=”+2\u00b70 m” option4=”\u20132\u00b70 m” correct=”option3″] This question was previously asked in UPSC NDA-2 – 2024 Download PDFAttempt Online For thin lenses in contact, the total power of … <\/p>\n

Detailed SolutionWhich one among the following is the correct focal length of a combina<\/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":[1103,1153,1128],"class_list":["post-89089","post","type-post","status-publish","format-standard","hentry","category-upsc-nda-2","tag-1103","tag-optics","tag-physics","no-featured-image-padding"],"yoast_head":"\nWhich one among the following is the correct focal length of a combina<\/title>\n<meta name=\"description\" content=\"For thin lenses in contact, the total power of the combination (P_total) is the algebraic sum of the individual powers (P\u2081, P\u2082). Given P\u2081 = 2.5 D and P\u2082 = -2.0 D, the total power is P_total = P\u2081 + P\u2082 = 2.5 D + (-2.0 D) = 0.5 D. The focal length (f) of a lens or lens combination is the reciprocal of its power (P), with power in dioptres (D) and focal length in meters (m). So, f_total = 1 \/ P_total = 1 \/ 0.5 D = 1 \/ (0.5 m\u207b\u00b9) = 2 m. The focal length is positive, indicating a converging lens combination. Power of a lens (P) is the reciprocal of its focal length (f) in meters (P = 1\/f). The power of a combination of thin lenses in contact is the sum of their individual powers. Positive power indicates a converging lens, and negative power indicates a diverging lens.\" \/>\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\/which-one-among-the-following-is-the-correct-focal-length-of-a-combina\/\" \/>\n<meta property=\"og:locale\" content=\"en_US\" \/>\n<meta property=\"og:type\" content=\"article\" \/>\n<meta property=\"og:title\" content=\"Which one among the following is the correct focal length of a combina\" \/>\n<meta property=\"og:description\" content=\"For thin lenses in contact, the total power of the combination (P_total) is the algebraic sum of the individual powers (P\u2081, P\u2082). Given P\u2081 = 2.5 D and P\u2082 = -2.0 D, the total power is P_total = P\u2081 + P\u2082 = 2.5 D + (-2.0 D) = 0.5 D. The focal length (f) of a lens or lens combination is the reciprocal of its power (P), with power in dioptres (D) and focal length in meters (m). So, f_total = 1 \/ P_total = 1 \/ 0.5 D = 1 \/ (0.5 m\u207b\u00b9) = 2 m. The focal length is positive, indicating a converging lens combination. Power of a lens (P) is the reciprocal of its focal length (f) in meters (P = 1\/f). The power of a combination of thin lenses in contact is the sum of their individual powers. Positive power indicates a converging lens, and negative power indicates a diverging lens.\" \/>\n<meta property=\"og:url\" content=\"https:\/\/exam.pscnotes.com\/mcq\/which-one-among-the-following-is-the-correct-focal-length-of-a-combina\/\" \/>\n<meta property=\"og:site_name\" content=\"MCQ and Quiz for Exams\" \/>\n<meta property=\"article:published_time\" content=\"2025-06-01T07:29:09+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":"Which one among the following is the correct focal length of a combina","description":"For thin lenses in contact, the total power of the combination (P_total) is the algebraic sum of the individual powers (P\u2081, P\u2082). Given P\u2081 = 2.5 D and P\u2082 = -2.0 D, the total power is P_total = P\u2081 + P\u2082 = 2.5 D + (-2.0 D) = 0.5 D. The focal length (f) of a lens or lens combination is the reciprocal of its power (P), with power in dioptres (D) and focal length in meters (m). So, f_total = 1 \/ P_total = 1 \/ 0.5 D = 1 \/ (0.5 m\u207b\u00b9) = 2 m. The focal length is positive, indicating a converging lens combination. Power of a lens (P) is the reciprocal of its focal length (f) in meters (P = 1\/f). The power of a combination of thin lenses in contact is the sum of their individual powers. Positive power indicates a converging lens, and negative power indicates a diverging lens.","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\/which-one-among-the-following-is-the-correct-focal-length-of-a-combina\/","og_locale":"en_US","og_type":"article","og_title":"Which one among the following is the correct focal length of a combina","og_description":"For thin lenses in contact, the total power of the combination (P_total) is the algebraic sum of the individual powers (P\u2081, P\u2082). Given P\u2081 = 2.5 D and P\u2082 = -2.0 D, the total power is P_total = P\u2081 + P\u2082 = 2.5 D + (-2.0 D) = 0.5 D. The focal length (f) of a lens or lens combination is the reciprocal of its power (P), with power in dioptres (D) and focal length in meters (m). So, f_total = 1 \/ P_total = 1 \/ 0.5 D = 1 \/ (0.5 m\u207b\u00b9) = 2 m. The focal length is positive, indicating a converging lens combination. Power of a lens (P) is the reciprocal of its focal length (f) in meters (P = 1\/f). The power of a combination of thin lenses in contact is the sum of their individual powers. Positive power indicates a converging lens, and negative power indicates a diverging lens.","og_url":"https:\/\/exam.pscnotes.com\/mcq\/which-one-among-the-following-is-the-correct-focal-length-of-a-combina\/","og_site_name":"MCQ and Quiz for Exams","article_published_time":"2025-06-01T07:29:09+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\/which-one-among-the-following-is-the-correct-focal-length-of-a-combina\/","url":"https:\/\/exam.pscnotes.com\/mcq\/which-one-among-the-following-is-the-correct-focal-length-of-a-combina\/","name":"Which one among the following is the correct focal length of a combina","isPartOf":{"@id":"https:\/\/exam.pscnotes.com\/mcq\/#website"},"datePublished":"2025-06-01T07:29:09+00:00","dateModified":"2025-06-01T07:29:09+00:00","author":{"@id":"https:\/\/exam.pscnotes.com\/mcq\/#\/schema\/person\/5807dafeb27d2ec82344d6cbd6c3d209"},"description":"For thin lenses in contact, the total power of the combination (P_total) is the algebraic sum of the individual powers (P\u2081, P\u2082). Given P\u2081 = 2.5 D and P\u2082 = -2.0 D, the total power is P_total = P\u2081 + P\u2082 = 2.5 D + (-2.0 D) = 0.5 D. The focal length (f) of a lens or lens combination is the reciprocal of its power (P), with power in dioptres (D) and focal length in meters (m). So, f_total = 1 \/ P_total = 1 \/ 0.5 D = 1 \/ (0.5 m\u207b\u00b9) = 2 m. The focal length is positive, indicating a converging lens combination. Power of a lens (P) is the reciprocal of its focal length (f) in meters (P = 1\/f). The power of a combination of thin lenses in contact is the sum of their individual powers. Positive power indicates a converging lens, and negative power indicates a diverging lens.","breadcrumb":{"@id":"https:\/\/exam.pscnotes.com\/mcq\/which-one-among-the-following-is-the-correct-focal-length-of-a-combina\/#breadcrumb"},"inLanguage":"en-US","potentialAction":[{"@type":"ReadAction","target":["https:\/\/exam.pscnotes.com\/mcq\/which-one-among-the-following-is-the-correct-focal-length-of-a-combina\/"]}]},{"@type":"BreadcrumbList","@id":"https:\/\/exam.pscnotes.com\/mcq\/which-one-among-the-following-is-the-correct-focal-length-of-a-combina\/#breadcrumb","itemListElement":[{"@type":"ListItem","position":1,"name":"Home","item":"https:\/\/exam.pscnotes.com\/mcq\/"},{"@type":"ListItem","position":2,"name":"UPSC NDA-2","item":"https:\/\/exam.pscnotes.com\/mcq\/category\/upsc-nda-2\/"},{"@type":"ListItem","position":3,"name":"Which one among the following is the correct focal length of a combina"}]},{"@type":"WebSite","@id":"https:\/\/exam.pscnotes.com\/mcq\/#website","url":"https:\/\/exam.pscnotes.com\/mcq\/","name":"MCQ and Quiz for Exams","description":"","potentialAction":[{"@type":"SearchAction","target":{"@type":"EntryPoint","urlTemplate":"https:\/\/exam.pscnotes.com\/mcq\/?s={search_term_string}"},"query-input":"required name=search_term_string"}],"inLanguage":"en-US"},{"@type":"Person","@id":"https:\/\/exam.pscnotes.com\/mcq\/#\/schema\/person\/5807dafeb27d2ec82344d6cbd6c3d209","name":"rawan239","image":{"@type":"ImageObject","inLanguage":"en-US","@id":"https:\/\/exam.pscnotes.com\/mcq\/#\/schema\/person\/image\/","url":"https:\/\/secure.gravatar.com\/avatar\/761a7274f9cce048fa5b921221e7934820d74514df93ef195a9d22af0c1c9001?s=96&d=mm&r=g","contentUrl":"https:\/\/secure.gravatar.com\/avatar\/761a7274f9cce048fa5b921221e7934820d74514df93ef195a9d22af0c1c9001?s=96&d=mm&r=g","caption":"rawan239"},"sameAs":["https:\/\/exam.pscnotes.com"],"url":"https:\/\/exam.pscnotes.com\/mcq\/author\/rawan239\/"}]}},"amp_enabled":true,"_links":{"self":[{"href":"https:\/\/exam.pscnotes.com\/mcq\/wp-json\/wp\/v2\/posts\/89089","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/exam.pscnotes.com\/mcq\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/exam.pscnotes.com\/mcq\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/exam.pscnotes.com\/mcq\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/exam.pscnotes.com\/mcq\/wp-json\/wp\/v2\/comments?post=89089"}],"version-history":[{"count":0,"href":"https:\/\/exam.pscnotes.com\/mcq\/wp-json\/wp\/v2\/posts\/89089\/revisions"}],"wp:attachment":[{"href":"https:\/\/exam.pscnotes.com\/mcq\/wp-json\/wp\/v2\/media?parent=89089"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/exam.pscnotes.com\/mcq\/wp-json\/wp\/v2\/categories?post=89089"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/exam.pscnotes.com\/mcq\/wp-json\/wp\/v2\/tags?post=89089"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}