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11.A 9cm long object is placed at 90cm from a spherical mirror perpendicular to its principal axis. A real imageis formed at 30cm from the mirror. What is the radius of curvature of the mirror? {Ans: - 45 cm) |
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Answer» Height of object ho = 9 cm Focal lenght of convex lens = ? cm Object distance u = -90 cm Image distance v = 30 cm Image height hi = ? Lens formula: 1/v - 1/u = 1/f 1/f = 1/v - 1/u = 1/30 + 1/(-90) = -1/45 ⇒ v = - 45 cm The image distance is 45 cm on the same side of the lens as the object. Magnification m = v/u = (-45)/(-90) = 1/2 = hi/ho = hi/9 ⇒ hi = 9/2 cm |
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