SSC
PHYSICS
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Question
[CLICK ON ANY CHOICE TO KNOW THE RIGHT ANSWER]
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20 cm
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18 cm
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10 cm
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5 cm
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Detailed explanation-1: -It is given that the image is smaller than the object if object is kept at a distance of 21 cm. Similarly, the image is bigger than the object if object is kept at a distance of 19 cm. Therefore, at 20 cm, the distance should be 2f. This means that the focal length is approximately 10 cm.
Detailed explanation-2: -Where should an object placed from a converging lens of focal length 20 cm, so as to obtain a real image of magnification 2? (C.B.S.E. 2001) [Ans, at 30 cm]
Detailed explanation-3: -Answer: The image is formed at a ‘distance of 16.66 cm’ away from the lens as a diminished image of height 3.332 cm. The image formed is a real image. The object distance is the distance between the object position and the lens position.
Detailed explanation-4: -When object is placed between convex lens and focal point, image formed is virtual and magnified which is shown in the diagram.