91Ó°ÊÓ

The contacts wom by a farsighted person allow her to see objects clearly that are as close as \(25.0 \mathrm{~cm}\), even though her uncorrected near point is \(79.0 \mathrm{~cm}\) from her eyes. When she is looking at a poster, the contacts form an image of the poster at a distance of \(217 \mathrm{~cm}\) from her eyes. (a) How far away is the poster actually located? (b) If the poster is \(0.350 \mathrm{~m}\) tall, how tall is the image formed by the contacts?

A farsighted person can read printing as close as \(25.0 \mathrm{~cm}\) when she wears contacts that have a focal length of \(45.4 \mathrm{~cm}\). One day, however, she forgets her contacts and uses a magnifying glass, as in Figure \(26-40 b\). It has a maximum angular magnification of 7.50 for a young person with a normal near point of \(25.0 \mathrm{~cm}\). What is the maximum angular magnification that the magnifying glass can provide for her?

An object is located \(30.0 \mathrm{~cm}\) to the left of a converging lens whose focal length is \(50.0 \mathrm{~cm} .\) (a) Draw a ray diagram to scale and from it determine the image distance and the magnification, (b) Use the thin-lens and magnification equations to verify your answers to part (a).

An object is in front of a converging lens \((f=0.30 \mathrm{~m})\). The magnification of the lens is \(m=4.0 .\) (a) Relative to the lens, in what direction should the object be moved so that the magnification changes to \(m=-4.0 ?\) (b) Through what distance should the object be moved?