The graph between 1 u and 1 v for a thin convex lens in order to determine its focal length is plotted as shown in the figure. The refractive index of lens is 1 . 5 and its both the surfaces have same

Question

The graph between 1 u and 1 v for a thin convex lens in order to determine its focal length is plotted as shown in the figure. The refractive index of lens is 1 . 5 and its both the surfaces have same radius of curvatures R . The value of R will be _____ cm . (Where u = object distance, v = image distance)

TestHub · Accepted Answer

For point B , 1 u = - 0 . 10 cm - 1 , 1 v = 0 ∴ Thus, u = - 10 cm , v = ∞ Using lens formula, 1 f = 1 v - 1 u = 0 - - 10 ⇒ f = 10 cm Now, using Lens maker's formula, 1 f = μ - 1 1 R 1 - 1 R 2 , where, μ is refractive index of lens. ⇒ 1 10 cm = 1 . 5 - 1 2 R = 1 R ⇒ R = 10 cm

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