Magnification

Magnifying glass enlarges the text of the bookIf you look in a flat mirror in a dressing room, your image is the same height as you are. A magnifying glass held above this page, however, produces an image of the page that is larger than the page itself. Curved optical elements—lenses and curved mirrors—can be used to create magnified images. In some cases, the magnified image is larger than the object; in others, the image is smaller than the object. Read the text aloud
Three different mirrors produce images with different magnifications
The magnification of a mirror or lens is the ratio of the image and object heights. Read the text aloud
(20.2) m= h i h o
m  = magnification
hi  = image size (m)
ho  = object size (m)
Magnification
Can you hold a concave mirror such that your image is inverted, i.e., upside-down? The values of the heights used in equation (20.2) can be either positive or negative depending on whether the image is upright (positive height) or inverted (negative height). Look at equation (20.2) again: A negative value for hi will produce a negative value for the magnification m. A negative magnification represents an inverted image, while a positive magnification is an upright image. Read the text aloud
What is the magnification?What is the magnification of the magnifying glass?
Asked: magnification m
Given: Object height: 17.5 squares (5 mm/square) are visible through the lens so the object “height” is 87.5 mm.
Image height: The image fills the lens so the image “height” is the diameter of the lens 135 mm (27 squares).
Relationships: m = hi / ho
Solution: m= h i h o = 135 mm 87.5 mm =1.54
Answer: The magnification is 1.54.
Read the text aloud Show Is the magnifying glass image inverted?
A biologist is observing a plant cell under a microscope. The microscope can be set to 50, 100, or 200 magnification. The cell is 185 micrometers wide (where 1 micrometer = 1 μm = 10−6 m). Which magnification will produce an image of the cell that is closest to 1 centimeter wide? Show

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