Question

A microscope with a tube length of 200 mm achieves a total magnification of 400

Answer 1

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A microscope with a tube length of 180 mm achieves a total magnification of 800\times with a 40x times objective and a 20x times eyepiece. The microscope is focused for viewing with a relaxed eye. How far is the sample from the objective lens?

Answer

The tube length is L = 180 mm
The total magnification is M = 800
The magnification of objective is Mo = 40
The magnification of eyepiece is Me = 20

Let the sample be at a distance p from the objective then

The distance of the image of the objective will be Io = MoP = 40P

This will be at L-40p from the eye piece

The distance of the image of the eyepiece will be Ie = Me(L-40P) = 20(L-40P)

The overall magnification

M = 20(L-40P)/P

800P = 20L - 800P

1600 P = 3600 mm

P = 2.25 mm