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M o d e l N o . O S - 8 5 1 5 B
Experiment 14: Microscope
Required Equipment from Basic Optics System
Bench
2 Convex Lenses (+100 mm and +200 mm)
Screen
Paper grid pattern (see page 45), or a 14 × 16 grid of 1 cm squares
Purpose
In this experiment, you will construct a microscope and determine its magnification.
Theory
d
o1
Object
Image
A microscope magnifies an object that is close to the objective lens. The microscope
in this experiment will form an image in the same place as the object (see Figure
14.1).
The lenses are thin compared to the other distances involved, which allows the Thin
Lens Formula to be used:
(eq. 14.1)
where f is focal length, d
distance between the image and the lens.
The magnification, M, of a two-lens system is equal to the product of the magnifica-
tions of the individual lenses:
(eq. 14.2)
Set Up
1.
Tape the paper grid pattern to the screen to serve as the object.
2.
The +100 mm lens is the objective lens (the one closer to the object). The +200
mm lens is the eyepiece lens (the one closer to the eye). Place the lenses near the
®
d
i2
Lens
+100 mm
Figure 14.1
1
1
1
-- -
=
---- -
+
--- -
f
d
d
o
i
is the distance between the object and the lens, and d
o
–
d
–
d
⎛
i1
⎞
⎛
--------- -
--------- -
M
=
M
M
=
1
2
⎜
⎟
⎜
d
d
o1
o2
⎠
E x p e r i m e n t 1 4 : M ic r o s c o p e
d
d
i1
o2
Lens
+200 mm
is the
i
i2
⎞
⎟
⎠
Eye
39
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