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Solve the question in attachment.( Class-X , Refraction of Light ) |
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Answer» tion:Let, the parallel beam is first incident on CONVEX lens.d = diameter of the beam = 5 mmNow, the image due to the convex lens should be formed on its focus (POINT B) So, for the concave lens,U= + 10 cm (SINCE, the virtual object is on the right of concave lens)f = 10 cmSo 1 - V 1 u 1 f 1 V 1 1 + = 0⇒v= -10 10So, the emergent beam becomes parallel after redfraction in concave lens. As shown from the triangles XYB and PQB,PQXYPQRBZB102012x 52.5 cm = 25mm2So, the beam diameter becomes 2.5 mm. SIMILARLY, it can be proved that if the light is incident of the concave side, the beam diameter will be 1 cm. |
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