PASCO OS-8515C Basic Optics System - Manual (Page 47)

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M o d e l N o . O S - 8 5 1 5 C E x p e r i m e n t 1 5 : T e l e s c o p e
47
Experiment 15: Telescope
Purpose
In this experiment, you will construct a telescope and determine its magnification.
Theory
Figure 15.1
An astronomical telescope consists of two convex lenses. The astronomical telescope
in this experiment will form an image in the same place as the object (see Figure
15.1).
The lenses are thin compared to the other distances involved, which allows the Thin
Lens Formula to be used:
(eq. 15.1)
where f is focal length, d
o
is the distance between the object and the lens, and d
i
is the
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. 15.2)
Set Up
1. Tape the paper grid pattern to the screen to serve as the object.
2. The +200 mm lens is the objective lens (the one closer to the object). The +100
mm lens is the eyepiece lens (the one closer to the eye). Place the lenses near one
Required Equipment from Basic Optics System
Bench
2 Convex Lenses (+100 mm and +200 mm)
Screen
Paper grid pattern (see page 57), or a 14 × 16 grid of 1 cm squares
+250 mm and -150 mm lenses (optional, for further study)
d
o1
-d
i2
d
i1
d
o2
Object
Image
Lens
+200 mm
Lens
+100 mm
Eye
1
f
---
1
d
o
-----
1
d
i
---- + =
M M
1
M
2
d
i1
–
d
o1
----------
⎝ ⎠
⎜ ⎟
⎛ ⎞ d
i2
–
d
o2
----------
⎝ ⎠
⎜ ⎟
⎛ ⎞
= =