{"id":3445,"date":"2025-07-21T14:33:33","date_gmt":"2025-07-21T14:33:33","guid":{"rendered":"https:\/\/odeacademy.in\/?p=3445"},"modified":"2025-07-21T17:08:27","modified_gmt":"2025-07-21T17:08:27","slug":"light-mirror-and-lenses","status":"publish","type":"post","link":"https:\/\/thequickknowledge.com\/exam\/light-mirror-and-lenses\/","title":{"rendered":"Light, Mirror and Lenses &#8211; Physics | General Science"},"content":{"rendered":"<h4 style=\"text-align: center;\">Light, Mirror, Lenses and Human Eyes<\/h4>\n<hr \/>\n<p>light travels in a straight line, and its interaction with objects creates shadows and images. It defines<\/p>\n<ul>\n<li>Pole (P): Midpoint of mirror surface<\/li>\n<li>Centre of Curvature (C): Centre of the sphere mirror<\/li>\n<li>Principal Axis: Line joining P and C<\/li>\n<li>Focus (F): Point where rays converge or appear to diverge<\/li>\n<li>Focal Length (f): Distance between P and F<\/li>\n<\/ul>\n<p>The relationship between radius of curvature (R) and focal length (f) with the formula <strong>R = 2f<\/strong><\/p>\n<p data-start=\"1326\" data-end=\"1349\"><strong data-start=\"1326\" data-end=\"1348\">Laws of reflection<\/strong>:<\/p>\n<ul data-start=\"1352\" data-end=\"1460\">\n<li>Angle of incidence = Angle of reflection<\/li>\n<li>Incident ray, normal, and reflected ray lie in the same plane<\/li>\n<\/ul>\n<p><strong>Image Formation &#8211; Various object positions<\/strong><\/p>\n<p><strong>Concave Mirrors<\/strong><\/p>\n<p><img fetchpriority=\"high\" decoding=\"async\" class=\"size-full wp-image-3449 aligncenter\" src=\"https:\/\/thequickknowledge.com\/exam\/wp-content\/uploads\/2025\/07\/concave-mirror-imgs.png\" alt=\"\" width=\"630\" height=\"455\" srcset=\"https:\/\/thequickknowledge.com\/exam\/wp-content\/uploads\/2025\/07\/concave-mirror-imgs.png 630w, https:\/\/thequickknowledge.com\/exam\/wp-content\/uploads\/2025\/07\/concave-mirror-imgs-300x217.png 300w\" sizes=\"(max-width: 630px) 100vw, 630px\" \/><\/p>\n<p><strong>Convex Mirrors<\/strong><\/p>\n<p><img decoding=\"async\" class=\" wp-image-3450 aligncenter\" src=\"https:\/\/thequickknowledge.com\/exam\/wp-content\/uploads\/2025\/07\/image-formation-by-convex-mirror-part-3.jpg\" alt=\"\" width=\"534\" height=\"223\" srcset=\"https:\/\/thequickknowledge.com\/exam\/wp-content\/uploads\/2025\/07\/image-formation-by-convex-mirror-part-3.jpg 496w, https:\/\/thequickknowledge.com\/exam\/wp-content\/uploads\/2025\/07\/image-formation-by-convex-mirror-part-3-300x125.jpg 300w\" sizes=\"(max-width: 534px) 100vw, 534px\" \/><\/p>\n<p><strong>Concave and Convex mirror uses<\/strong><\/p>\n<ul>\n<li><strong>Concave Mirror Uses:<\/strong> Torches, shaving, headlights, dentist mirrors, solar furnaces.<\/li>\n<li><strong>Convex Mirror Uses:<\/strong> Rear-view mirrors (wide view).<\/li>\n<\/ul>\n<p><span data-huuid=\"9137385152652561936\"><strong>Formula\u00a0<\/strong><\/span><\/p>\n<ul>\n<li><span style=\"font-size: 16px;\"><span data-huuid=\"9137385152652561936\">The mirror formula: 1\/f<strong>\u00a0 = <\/strong><\/span>1\/v + 1\/u\u00a0<\/span><\/li>\n<li><span data-huuid=\"9137385152652560270\">The magnification formula is: m = <span class=\"mord mathnormal\">h<\/span><span class=\"msupsub\"><span class=\"vlist-t\"><span class=\"vlist-r\"><span class=\"vlist\"><span class=\"sizing reset-size6 size3 mtight\"><span class=\"mord mtight\">\u2032\/h = (-v)\/u<\/span><\/span><\/span><\/span><\/span><\/span><\/span><\/li>\n<\/ul>\n<p><strong>Laws of Refraction of Light<\/strong><\/p>\n<ul>\n<li>Law 1: The incident ray, refracted ray, and the normal to the interface of two transparent media all lie in the same plane.<\/li>\n<li>Law 2 (Snell\u2019s Law): (sin i\/sin r) = constant (This constant is known as the refractive index for the given pair of media and light colour)<\/li>\n<\/ul>\n<p><strong>The Refractive Index<\/strong><\/p>\n<p><span style=\"font-size: 16px;\">Refraction occurs because light travels at different speeds in different media. <\/span><\/p>\n<ul>\n<li>Absolute refractive index: c\/v (where <strong>c<\/strong> is speed of light in air\/vacuum and <strong data-start=\"799\" data-end=\"804\">v<\/strong> in the medium.)<\/li>\n<li>Medium refractive index : Air = 1.0003, Water = 1.33, Crown glass = 1.52, Diamond = 2.42<\/li>\n<\/ul>\n<p>Light bends towards the normal when entering a denser medium (air to glass). It bends away from the normal when exiting to a rarer medium (glass to air). The emergent ray is parallel to the incident ray but laterally displaced.<\/p>\n<p><strong>Optical Density vs Mass Density<\/strong> &#8211; Optical density is not equal to mass density. Kerosene has higher optical density than water but lower mass density.<\/p>\n<p><strong>Lenses<\/strong><\/p>\n<p>A lens is a transparent material bounded by two surfaces, at least one of which is spherical.<\/p>\n<ul>\n<li><strong>Convex lens :<\/strong> Thicker in the middle, converges rays. (Also called converging lens)<\/li>\n<li>Convex Lens converges parallel rays to a point called the principal focus. The point on the axis is the focal point (F). The focal length (f) is the distance between the lens and F.<\/li>\n<li>Convex lenses have <strong data-start=\"686\" data-end=\"708\">two principal foci &#8211; <\/strong><span class=\"katex\"><span class=\"katex-mathml\">F1<\/span><\/span>\u00a0and <span class=\"katex\"><span class=\"katex-mathml\">F2<\/span><span class=\"katex-html\" aria-hidden=\"true\"><span class=\"base\"><span class=\"mord\"><span class=\"msupsub\"><span class=\"vlist-t vlist-t2\"><span class=\"vlist-r\"><span class=\"vlist-s\">\u200b<\/span><\/span><\/span><\/span><\/span><\/span><\/span><\/span>, and the same applies to concave lenses.<\/li>\n<li>Concave lens: Thicker at edges, diverges rays. (Also called diverging lens)<\/li>\n<li><strong data-start=\"547\" data-end=\"563\">Concave Lens<\/strong> diverges parallel rays such that they appear to come from a point on the axis\u2014the <strong data-start=\"646\" data-end=\"663\">virtual focus<\/strong>.<\/li>\n<\/ul>\n<p>A lens has two centres of curvature (C\u2081 and C\u2082) and one principal axis. The optical centre is the central point of the lens.<\/p>\n<p><strong>Concex Lens<\/strong><\/p>\n<table>\n<thead>\n<tr>\n<th>Object Position<\/th>\n<th>Image Position<\/th>\n<th>Image Size<\/th>\n<th>Nature<\/th>\n<\/tr>\n<\/thead>\n<tbody>\n<tr>\n<td>At infinity<\/td>\n<td>At focus <span class=\"katex\">F2<\/span><\/td>\n<td>Highly diminished<\/td>\n<td>Real and inverted<\/td>\n<\/tr>\n<tr>\n<td>Beyond <span class=\"katex\">2F1<\/span><\/td>\n<td>Between <span class=\"katex\">F2<\/span>\u00a0and <span class=\"katex\">2F2<\/span><\/td>\n<td>Diminished<\/td>\n<td>Real and inverted<\/td>\n<\/tr>\n<tr>\n<td>At <span class=\"katex\">2F1<\/span><\/td>\n<td>At <span class=\"katex\">2F2<\/span><\/td>\n<td>Same size<\/td>\n<td>Real and inverted<\/td>\n<\/tr>\n<tr>\n<td>Between <span class=\"katex\">F1 <\/span>and <span class=\"katex\">2F1<\/span><\/td>\n<td>Beyond <span class=\"katex\">2F2<\/span><\/td>\n<td>Enlarged<\/td>\n<td>Real and inverted<\/td>\n<\/tr>\n<tr>\n<td>At focus <span class=\"katex\">F1<\/span><\/td>\n<td>At infinity<\/td>\n<td>No image<\/td>\n<td>&#8212;<\/td>\n<\/tr>\n<tr>\n<td>Between <span class=\"katex\">F1<\/span>\u00a0&amp; O<\/td>\n<td>Same side as object<\/td>\n<td>Enlarged<\/td>\n<td>Virtual, erect<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<p>Concex Lens<\/p>\n<table>\n<thead>\n<tr>\n<th>Object Position<\/th>\n<th>Image Position<\/th>\n<th>Image Size<\/th>\n<th>Nature<\/th>\n<\/tr>\n<\/thead>\n<tbody>\n<tr>\n<td>At infinity<\/td>\n<td>At focus <span class=\"katex\">F1<\/span><\/td>\n<td>Highly diminished<\/td>\n<td>Virtual, erect<\/td>\n<\/tr>\n<tr>\n<td>Between infinity and optical center O<\/td>\n<td>Between <span class=\"katex\">F1<\/span>\u00a0&amp; O<\/td>\n<td>Diminished<\/td>\n<td>Virtual, erect<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<p><strong>Formula<\/strong><\/p>\n<ul>\n<li>Lens formula = 1\/f = (1\/v) &#8211; (1\/u)<\/li>\n<li>Magnification (m) = <span data-huuid=\"9137385152652560270\">m = <span class=\"mord mathnormal\">h<\/span><span class=\"msupsub\"><span class=\"vlist-t\"><span class=\"vlist-r\"><span class=\"vlist\"><span class=\"sizing reset-size6 size3 mtight\"><span class=\"mord mtight\">\u2032\/h = (v)\/u<\/span><\/span><\/span><\/span><\/span><\/span><\/span><\/li>\n<\/ul>\n<p data-start=\"517\" data-end=\"558\"><strong data-start=\"524\" data-end=\"558\">Power of a Lens<\/strong><\/p>\n<ul data-start=\"560\" data-end=\"735\">\n<li>Power <span class=\"katex\"><span class=\"katex-mathml\">P=1\/f<\/span><\/span>\u00a0(f in metres)<strong data-start=\"596\" data-end=\"606\">\u00a0Unit<\/strong>: Dioptre (D), <strong>[<\/strong>1 D = 1 m\u207b\u00b9<strong>]<\/strong><\/li>\n<li data-start=\"636\" data-end=\"660\"><strong data-start=\"663\" data-end=\"681\">Positive (<\/strong>Convex lens),\u00a0<strong data-start=\"700\" data-end=\"718\">Negative power<\/strong> (Concave lens)<\/li>\n<li data-start=\"636\" data-end=\"660\">Lenses in combination: Total power P=P1+P2+P3+&#8230;&#8230;&#8230;Pn (Used in optical instruments, spectacles, microscopes, etc.)<\/li>\n<\/ul>\n<p><strong>Human Eyes<\/strong><\/p>\n<p>The eye functions like a camera, with its lens system focusing images onto the retina. Key components include the cornea, iris, pupil, crystalline lens, and retina.\u00a0Iris controls the pupil size and regulates light entry. The ability of the eye to adjust its focal length, known as accommodation, allows us to see objects at varying distances. Least distance of distinct vision = 25 cm (for a normal adult eye).<\/p>\n<p data-start=\"1496\" data-end=\"1518\"><strong data-start=\"1496\" data-end=\"1517\">Defects of vision<\/strong>:<\/p>\n<ul>\n<li data-start=\"1523\" data-end=\"1619\"><strong data-start=\"1624\" data-end=\"1641\">Hypermetropia<\/strong> (Farsightedness): Cannot see near objects clearly; corrected with <strong data-start=\"1708\" data-end=\"1725\">convex lenses<\/strong>.<\/li>\n<li data-start=\"1523\" data-end=\"1619\"><strong data-start=\"1523\" data-end=\"1533\">Myopia<\/strong> (Nearsightedness): Cannot see far objects clearly; corrected with <strong data-start=\"1600\" data-end=\"1618\">concave lenses<\/strong>.<\/li>\n<li data-start=\"1523\" data-end=\"1619\"><strong data-start=\"1731\" data-end=\"1745\">Presbyopia<\/strong>: Age-related loss of accommodation; often corrected using <strong data-start=\"1804\" data-end=\"1822\">bifocal lenses<\/strong>.<\/li>\n<\/ul>\n<p data-start=\"1826\" data-end=\"1896\"><strong data-start=\"1826\" data-end=\"1838\">Cataract<\/strong>: Clouding of the eye lens, treatable through <strong data-start=\"1884\" data-end=\"1895\">surgery<\/strong>.<\/p>\n<p><strong>Dispersion<\/strong> is the splitting of white light into its colors.\u00a0the separation of white light into its component colors (VIBGYOR).<\/p>\n<p data-start=\"698\" data-end=\"1011\"><strong data-start=\"698\" data-end=\"724\">Atmospheric refraction<\/strong> causes effects such as the <strong data-start=\"752\" data-end=\"774\">twinkling of stars<\/strong>, <strong data-start=\"776\" data-end=\"795\">advance sunrise<\/strong>, and <strong data-start=\"801\" data-end=\"819\">delayed sunset<\/strong>. Stars appear to twinkle due to continuous refraction of their light through Earth&#8217;s atmosphere, which is not uniform. Planets, being closer and having a larger apparent size, do not twinkle.<\/p>\n<p data-start=\"1013\" data-end=\"1256\"><strong>Scattering of light<\/strong> explains the <strong data-start=\"1054\" data-end=\"1079\">blue color of the sky<\/strong> and <strong data-start=\"1084\" data-end=\"1113\">red appearance of the Sun<\/strong> during sunrise and sunset. Smaller particles scatter shorter (blue) wavelengths more, while larger particles scatter longer (red) wavelengths.<\/p>\n<p data-start=\"1013\" data-end=\"1256\"><strong>Tyndall Effect<\/strong> explains why light beams become visible in smoke\/fog.<\/p>\n<div class=\"CM8kHf j86kh\" data-hveid=\"CAkQAQ\">\n<div data-expression=\"\\frac{1}{v} + \\frac{1}{u} = \\frac{1}{f}\"><\/div>\n<\/div>\n<hr \/>\n<p><span style=\"color: #ff0000;\"><strong>Related Links<\/strong><\/span><\/p>\n<ul>\n<li><strong>General Science : Questions for Competitive Exams<\/strong> \ud83d\udd17<\/li>\n<\/ul>\n<p><strong><a href=\"https:\/\/thequickknowledge.com\/exam\/general-science\/\">General Science<\/a>, <a href=\"https:\/\/thequickknowledge.com\/exam\/study-materials\/\">Study Materials<\/a>, <a href=\"https:\/\/thequickknowledge.com\/exam\/current-affairs\/\">Current Affairs<\/a>, <a href=\"https:\/\/thequickknowledge.com\/exam\/practice-questions\/\">Practice Questions<\/a>,\u00a0<\/strong><\/p>\n","protected":false},"excerpt":{"rendered":"<p>Light, Mirror, Lenses and Human Eyes light travels in a straight line, and its interaction with objects creates shadows and images. It defines Pole (P): Midpoint of mirror surface Centre of Curvature (C): Centre of the sphere mirror Principal Axis: Line joining P and C Focus (F): Point where rays converge or appear to diverge [&hellip;]<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"site-sidebar-layout":"no-sidebar","site-content-layout":"","ast-site-content-layout":"default","site-content-style":"default","site-sidebar-style":"default","ast-global-header-display":"","ast-banner-title-visibility":"","ast-main-header-display":"","ast-hfb-above-header-display":"","ast-hfb-below-header-display":"","ast-hfb-mobile-header-display":"","site-post-title":"","ast-breadcrumbs-content":"","ast-featured-img":"disabled","footer-sml-layout":"","ast-disable-related-posts":"","theme-transparent-header-meta":"default","adv-header-id-meta":"","stick-header-meta":"","header-above-stick-meta":"","header-main-stick-meta":"","header-below-stick-meta":"","astra-migrate-meta-layouts":"set","ast-page-background-enabled":"default","ast-page-background-meta":{"desktop":{"background-color":"var(--ast-global-color-4)","background-image":"","background-repeat":"repeat","background-position":"center center","background-size":"auto","background-attachment":"scroll","background-type":"","background-media":"","overlay-type":"","overlay-color":"","overlay-opacity":"","overlay-gradient":""},"tablet":{"background-color":"","background-image":"","background-repeat":"repeat","background-position":"center center","background-size":"auto","background-attachment":"scroll","background-type":"","background-media":"","overlay-type":"","overlay-color":"","overlay-opacity":"","overlay-gradient":""},"mobile":{"background-color":"","background-image":"","background-repeat":"repeat","background-position":"center center","background-size":"auto","background-attachment":"scroll","background-type":"","background-media":"","overlay-type":"","overlay-color":"","overlay-opacity":"","overlay-gradient":""}},"ast-content-background-meta":{"desktop":{"background-color":"var(--ast-global-color-5)","background-image":"","background-repeat":"repeat","background-position":"center center","background-size":"auto","background-attachment":"scroll","background-type":"","background-media":"","overlay-type":"","overlay-color":"","overlay-opacity":"","overlay-gradient":""},"tablet":{"background-color":"var(--ast-global-color-5)","background-image":"","background-repeat":"repeat","background-position":"center center","background-size":"auto","background-attachment":"scroll","background-type":"","background-media":"","overlay-type":"","overlay-color":"","overlay-opacity":"","overlay-gradient":""},"mobile":{"background-color":"var(--ast-global-color-5)","background-image":"","background-repeat":"repeat","background-position":"center center","background-size":"auto","background-attachment":"scroll","background-type":"","background-media":"","overlay-type":"","overlay-color":"","overlay-opacity":"","overlay-gradient":""}},"footnotes":""},"categories":[137],"tags":[138],"class_list":["post-3445","post","type-post","status-publish","format-standard","hentry","category-general-science","tag-general-science-notes"],"aioseo_notices":[],"_links":{"self":[{"href":"https:\/\/thequickknowledge.com\/exam\/wp-json\/wp\/v2\/posts\/3445","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/thequickknowledge.com\/exam\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/thequickknowledge.com\/exam\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/thequickknowledge.com\/exam\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/thequickknowledge.com\/exam\/wp-json\/wp\/v2\/comments?post=3445"}],"version-history":[{"count":3,"href":"https:\/\/thequickknowledge.com\/exam\/wp-json\/wp\/v2\/posts\/3445\/revisions"}],"predecessor-version":[{"id":3448,"href":"https:\/\/thequickknowledge.com\/exam\/wp-json\/wp\/v2\/posts\/3445\/revisions\/3448"}],"wp:attachment":[{"href":"https:\/\/thequickknowledge.com\/exam\/wp-json\/wp\/v2\/media?parent=3445"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/thequickknowledge.com\/exam\/wp-json\/wp\/v2\/categories?post=3445"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/thequickknowledge.com\/exam\/wp-json\/wp\/v2\/tags?post=3445"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}