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Find magnifications of image

A 60 cm tall red rose is placed 40 cm from a large convex lens of focal length 20 cm.
Locate the position of the image by means of a ray diagram
Locate the position of the image by means of the mirror equation
Find the magnification of the image
What is the height of the image?

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Steve S. | Tutoring in Precalculus, Trig, and Differential CalculusTutoring in Precalculus, Trig, and Diffe...
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See GeoGebra ray diagram here:

From ray diagram image is 40 cm from lens on opposite side as object.


1/OD + 1/ID = 1/FL

1/40 + 1/ID = 1/20

1/ID = 2/40 - 1/40 = 1/40

ID = 40 cm on opposite side of lens as object

M = -ID/OD = -40/40 = -1,
where negative means image is inverted.
1 means same size as object.

So height of image is same as object, 60 cm.