Q29 of 61 Page 1

A student obtained an image of a distant object on a screen to determine the focal length F1 of the given lens. His teacher after checking the image, gave him another lens of focal length F2 and asked to focus the same object on the same screen. The student found that to obtain a sharp image he has to move the lens away from A screen. From this finding we may conclude that both the lenses given to the student were:

The correct answer is: option (b)

Both of the lenses given to the student were convex lens and the focal length of second lens is greater than the focal length of the first lens. Since the object was obtained on the screen, so the image formed was real. So, the lens is convex lens. The object distance is decreasing because the image distance is increasing. So, F1 < F2.

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