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Physics - Geometrical Optics Question with Solution | TestHub

PhysicsGeometrical OpticsRefraction at curved surface/LensEasy2 minPYQ_2020

PhysicsEasysingle choice

A convex lens is used to obtain a magnified image of an object on a screen. The object is at a distance $10 m$ from the lens. If the magnification is $19$ . the focal length of the lens is

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Here $u = - 10 m$ , $m = 19$ $∴ m = - \frac{υ}{u} \Rightarrow 19 = \frac{- υ}{- 10} \Rightarrow V = 190 m$ Using the lens formula, $\frac{1}{f} = \frac{1}{v} - \frac{1}{u}$ $\begin{array}{l} \frac{1}{f} = \frac{1}{190} - \frac{1}{- 10} \\ \Rightarrow \frac{1}{f} = \frac{1}{190} + \frac{1}{10} \\ \Rightarrow \frac{1}{f} = \frac{1 + 19}{190} \\ \Rightarrow f = \frac{190}{20} = 9.5 m \end{array}$ Hence, the focal length of lens = $9.5 m$

Stream:NTA_ABHYAS_NEETSubject:PhysicsTopic:Geometrical OpticsSubtopic:Refraction at curved surface/Lens

⏱ 2mℹ️ Source: PYQ_2020

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