Physics
AB is an object and PQ is its real, inverted image. The lengths of AB and PQ are equal. This is possible when a lens is present between the object and its image.
(a) What kind of lens is used here? Also, state the position of the lens and where it is to be placed.
(b) Name a device where this lens action is used.
Answer
(a) Convex lens, at the midpoint of the distance between the object and the image.
(b) Photocopier
Explanation:
(a) The diagram shows a real, inverted image (PQ) of the object (AB) with equal size, which gives us a strong clue that this behaviour is characteristic of a convex lens. When an object is placed at 2F (twice the focal length) from a convex lens : The image is also formed at 2F on the other side.So,
- Lens used : Convex lens
- Position of object : At 2F
- Position of lens : Exactly midway between the object (AB) and image (PQ), since both are at 2F from the lens.
(b) Photocopier / xerox machine / intermediate lens in a terrestrial telescope.
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