{"id":34922,"date":"2016-11-30T16:18:24","date_gmt":"2016-11-30T10:48:24","guid":{"rendered":"https:\/\/www.cbselabs.com\/?p=34922"},"modified":"2021-09-18T15:26:34","modified_gmt":"2021-09-18T09:56:34","slug":"focal-length-of-spherical-lenses","status":"publish","type":"post","link":"https:\/\/www.cbselabs.com\/focal-length-of-spherical-lenses\/","title":{"rendered":"Focal Length of Spherical Lenses"},"content":{"rendered":"
Physics Lab Manual<\/a>NCERT Solutions <\/a>Class 12 Physics Sample Papers<\/a><\/p>\n Spherical lens\u00a0<\/strong><\/span> (c) Different types of convex lenses: <\/strong>The three types of convex lenses are<\/p>\n (d) Different types of concave lenses:<\/strong> The three types of concave lenses are<\/p>\n Terms associated with spherical lenses\u00a0<\/strong><\/span><\/p>\n Three special rays<\/strong><\/span> Sign convention\u00a0<\/strong><\/span> (c) Facts: <\/strong>According to above mentioned rules of sign convention,<\/p>\n Lens formula<\/strong><\/span> Assumptions made<\/strong><\/span> Position, nature and size of image when object is put in different position in front of a convex lens\u00a0<\/strong><\/span> Power of a lens\u00a0<\/strong><\/span> Lens combination\u00a0<\/strong><\/span> Chromatic aberration of a lens\u00a0<\/strong><\/span> Focal Length of Spherical Lenses Physics Lab ManualNCERT Solutions Class 12 Physics Sample Papers Spherical lens\u00a0 (\u0430) Definition: A piece of a transparent medium bounded by atleast one spherical surface, is called a spherical lens. (b) Types: There are two types of spherical lenses. Convex or Converging Lenses: These are thick in the middle and …<\/p>\n","protected":false},"author":27,"featured_media":0,"comment_status":"closed","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"spay_email":""},"categories":[2],"tags":[],"yoast_head":"\n
\n(\u0430) Definition:<\/strong> A piece of a transparent medium bounded by atleast one spherical surface, is called a spherical lens.
\n(b) Types: <\/strong>There are two types of spherical lenses.<\/p>\n\n
\n
\n
\n<\/li>\n<\/ol>\n\n
\nIn diagram \u00a0AB is the aperture of the lens.<\/li>\n
\n<\/li>\n
\nIn diagram, O is the optical centre of the lens.<\/li>\n
\nIn diagram,F1<\/sub> is the first principal focus of the lens. (For object at F1<\/sub> image at infinity).<\/li>\n
\nIn diagram, F2<\/sub> is the second principal focus of the lens (For image at F2<\/sub> object at infinity).<\/li>\n
\nIn diagram, the shaded portion is the principal section of the lens cut by the plane of the book page.<\/li>\n<\/ol>\n
\n The special rays are :<\/strong><\/p>\n\n
\n<\/li>\n
\nAfter refraction from the lens, it goes parallel to the principal axis.<\/li>\n
\n(a) Definition:<\/strong> It is a convention, which fixes the sign of different distances measured. The sign convention followed is the New Cartesian sign convention.
\n(b) Rules:<\/strong> It gives following rules:<\/p>\n\n
\n<\/li>\n<\/ol>\n\n
\nThe equation relating the object distance (u), the image distance (u) and the lens focal length (f), is called lens formula. It is also called Gaussian formula.
\n<\/p>\n
\nFollowing assumptions are made in derivation of the lens formula.<\/p>\n\n
\n\u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 It is described below in tabular form.<\/strong>
\n
\n
\n<\/p>\n
\n(a) Definition:<\/strong> It is the capacity or ability of a lens to deviate (converge or diverge) the path of rays passing through it. A lens producing more converging or more diverging is said to have more power and vice-versa.
\nIt is represented by the symbol P.
\n(b) Relation with focal length:<\/strong> A lens of less focal length produces more converging or diverging rays and is said to have more power.
\n
\n(c) Unit:<\/strong> Unit of power is dioptre (D). One dioptre is the power of a lens of focal length 1 metre.
\n
\n(d) Sign:<\/strong> A converging lens has positive focal length and positive power.
\nA diverging lens has negative focal length and negative power.<\/p>\n
\n(a) Definition:<\/strong> Two or more thin lenses, placed in contact together to have a common principal axis, form a lens combination.
\n(b) Focal length:<\/strong> If f1<\/sub>, f2<\/sub>,….., fn<\/sub> be the focal length of individual lens and F be the focal
\nlength of the combination.
\n
\nNote:<\/strong> The lenses forming the combination must be thin to have their optical centres coinciding at one point to represent optical centre of the combination.
\n(c) Power:<\/strong> If P1<\/sub>, P2<\/sub>,….., Pn<\/sub> be the power of individual lenses and P be the power of the
\ncombination.
\n
\n(d) Magnification:<\/strong> If m1<\/sub>, m2<\/sub>,….., mn<\/sub> are the magnification of individual lenses and m is the equivalent magnification of the combination then,
\n<\/p>\n
\n(a) Definition:<\/strong> The defect or drawback of a lens due to which it makes a coloured image of an object illuminated with white light, is called chromatic aberration. It is due to dispersion of white light by lens (just like a prism does).
\n(b) Remedy: <\/strong>It is removed by combining a convex and a concave lens of suitable focal length and material.
\nThe combination of two lenses is called an achromatic combination (achromic doublet).<\/p>\n","protected":false},"excerpt":{"rendered":"