A convex lens forms a real and inverted imaged an object on a screen kept at a distance of 50 cm from it At what distance should the object be placed from the screen so that the size of the image formed is equal to the size of the object.what is the focal length of the lens used?

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Solution

Since same size real and iverted image,object must be placed in the center of curvature.since the image is forMed at 2f2 that is the other center of curvature,hence the distance between 2f 1and object is 50cm.therefore focal lenght =50/2=25cm

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