Thu May 05, 2011 By: Akankshya Sahu

Position of image approaches focus of lens only when object approaches infinity. Why is this statement false?

Expert Reply
Thu May 05, 2011
A positive or converging lens in air will focus a collimated beam travelling along the lens axis to a spot (known as the focal point) at a distance f from the lens. Conversely, a point source of light placed at the focal point will be converted into a collimated beam by the lens. These two cases are examples of image formation in lenses. In the former case, an object at an infinite distance (as represented by a collimated beam of waves) is focused to an image at the focal point of the lens. In the latter, an object at the focal length distance from the lens is imaged at infinity. The plane perpendicular to the lens axis situated at a distance f from the lens is called the focal plane.
The final image of object will be formed at infinity if the object approaches towards the lens,therefore Statement-1: Position of image approaches focus of a lensonly when object approaches infinity.
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