Chapter 11.pdf

Example Problem 11.3An electron microscope magnifies a virus that is 3.50 × 10 –7 m. Ifthe magnification is 3.70 × 10 5 , how big will the image be?GivenObject height h o= 3.50 × 10 –7 mMagnification M = 3.70 × 10 5RequiredImage height h i= ?Analysis and SolutionThe correct equation is M =h ih oRearrange it to solve for the variable needed: h i= Mh oSubstitute the values and their units, and solve the problem.h i= Mh oh i= (3.70 × 10 5 )(3.50 × 10 –7 m)= 0.130 mParaphraseThe size of the image is 0.130 m or 13.0 cm.Practice Problems1. A slide projector has amagnification of 50. Howwide will the projectedimage be if the slide is2.8 cm wide?2. A concave mirror creates avirtual image of a candleflame that is 10 cm high. Ifthe magnification of themirror is 12.5, what is theheight of the candle flame?3. A magnifying glass willmagnify 6 times. If themagnifying glass is heldover a page and magnifiesa letter that is 2 mm tall,how big is the image?Example Problem 11.4A concave mirror creates a real, inverted image 16.0 cm from itssurface. If the image is 4.00 times larger, how far away is the object?GivenImage distance d i= 16.0 cmMagnification M = 4.00RequiredObject distance d o= ?Analysis and SolutionThe correct equation is M = d id oRearrange it to solve for the variable needed: d o=Substitute the values and their units, and solve the problem.d id o=Md o= 16.0 cm4.00= 4.00 cmd iMPractice Problems1. An insect is magnified12 times by a concavemirror. If the image is real,inverted, and 6 cm fromthe mirror, how far away isthe insect?2. A lens produces a realimage that is 23 timesbigger than the object. Ifthe object is 14 cm away,how far away is the image?3. A human hair is placed3 mm from a powerfulmicroscope lens that has amagnification of 40 times.How far from the lens willthe image be formed?ParaphraseThe object is 4.00 cm from the mirror.Ray diagrams model the behaviour of light in mirrors and lenses.425