An office copier uses a lens to place an image of a document onto a rotating dru
ID: 2020681 • Letter: A
Question
An office copier uses a lens to place an image of a document onto a rotating drum. The copy is made from this image. (a) What kind of lens is used? Should it be 1 - converging, or 2 - diverging? (Give the number of the correct answer.)Suppose the lens has a focal length of magnitude 14.0 cm. If the document and its copy are to have the same size, but are inverted with respect to one another, (b) how far from the document is the lens located and (c) how far from the lens is the image located?
I know that answer a will be converging. But i do not know how to do b and c. Please explain.
Explanation / Answer
Yeah, part a has to be a convering lens because only a converging lens can create a real image.
Part b: they tell you the image and object are the same size. This can only happen if the object distance and image distance are each twice the focal length. So
(b) document is 20 cm from the lens and
(c) image is also 20 cm from the lens.