Problem 27.60 Part A The medium-power objective lens in a laboratory microscope

Question

Problem 27.60 Part A The medium-power objective lens in a laboratory microscope has a focal length fobjective = 3.75 mm. If this lens produces a lateral magnification of -43.0, what is its 'working distance'; that is, what is the distance from the object to the objective lens? Express your answer using three significant figures. Part B What is the focal length of an eyepiece lens that will provide an overall magnification of -115? Assume student's near-point distance is N = 25 cm. Express your answer using two significant figures.

Explanation / Answer

Part A

f = 3.75 mm
lateral magnification,m = -43.0
m = -di/do
-43 = - di/do
di = 43 do

now, 1/ f = 1/do + 1/di   = (43*do+do)/(43*do*do) = 44*/43do
1/3.75 = 44/43*do

do = 44/43 * 3.75
do = 3.837 mm

part B

m = -di/fobjective

-115 = - 25/fobjective

fobjective = 25/115 = 0.218 cm

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