A mirror is used to produce an image with magnification of 4 1 . If the distance between object and its image is 40 cm , then the focal length of the mirror is ________

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A mirror is used to produce an image with magnification of 4 1 ​ . If the distance between object and its image is 40 cm , then the focal length of the mirror is ________

TestHub · Accepted Answer

​ m = − u v ​ = − ( − u v ​ ) = u v ​ 4 1 ​ = u v ​ ⇒ u = 4 v v + u = 40 5 v = 40 v = 8 cm u = 32 cm v 1 ​ + u v ​ = f 1 ​ 8 1 ​ − 32 1 ​ = f 1 ​ 32 4 − 1 ​ = f 1 ​ f = 3 32 ​ = 10.7 cm ​

Physics - Geometrical Optics Question with Solution | TestHub

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