InterviewSolution
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InterviewSolution
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A convex lens, of focal length 20 cm, has a point object placed on its principal axis at distance of 40 cm from it. A plane mirror is placed 30 cm behind the convex lens. Locate the position of image formed by this combination |
Answer» SOLUTION : We first CONSIDER the effect of the lens. For the lens, we have u=-40 cm and f= + 20 cm Using the lens formula, we get ` (1)/(v_1) - (1)/(-40) = 1/20 "" thereforev_1= + 40cm` Had there been the lens only the image WOULD have have been formed at `Q_1` . The plane mirror M is at a distance of 30 cm from the lens L. We can,therefore, think of `Q_1` as a VIRTUAL object, located at a distance of 10 cm, behind the plane mirror M. The plane mirror therefore forms a real image (of this virtual object `Q_1`) at Q, 10 cm in front of it. |
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