PASCO OS-8500 INTRODUCTORY OPTICS SYSTEM - Manual (Page 53)

012-02744K Introductory Optics System
®
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EQUIPMENT NEEDED:
-Optics Bench -75 mm Focal Length Convex Lens
-150 mm Focal Length Convex Lens -Component Holders (2)
Experiment 21: The Telescope
Figure 21.1 The Telescope
Introduction
Telescopes are used to obtain magnified images of distant objects. As you can see by looking at
Table 18.1 from Experiment 18, the image of a distant object when viewed through a single
converging lens will be focused nearly at the focal point of the lens. This image will be real,
inverted, and reduced in size. In fact, the greater the distance of the object (with respect to f), the
smaller the size of the image.
However, this reduced image is useful. By viewing this image through a second converging
lens—used as a magnifier—an enlarged image can be seen.
Figure 21.2 Telescope Magnification
f
1
f
2
f
2
f
1
f
1
+ f
2
= 225 mm
Line of sight
L
2
(75 mm Lens)
L
1
(150 mm Lens)
L
2
L
1
f
1
h
0
f
1
,f
2
θ
2
θ
1 h
i
f
2
h
0
θ
1