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PROGRAM
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DIVERSEN
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EDITH13
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LENS.ZIP
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LENS.EDH
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1995-02-06
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Version 010F
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Galliean Telescope
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Topic Text -----------------------------
{keep}{embed=lens.dll,Lens,70:15:2:204:52:-451:-52:339}
{fontsize=40}{bold}Galliean Telescope{fontsize=20}
The earliest from of terrestrial telescope is called the Gallilean telescope.
It uses a diverging lens nearest the eye
(right-hand side) and a converging lens furthest from the eye.
A Gallilean telescope is shorter than an {link=4,astronomical telescope} so
it is often used for opera glasses.
However it has a small field of view and it is impossible for the eye to collect all the light
which passes though the objective lens so the image is always dark.
See also:\
{link=1,One Lens}\
{link=2,Two Lenses}\
{link=4,Telescope}\
{link=3,Microscope}\
\end
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Telescope
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Topic Text -----------------------------
{keep}{embed=lens.dll,Lens,70:15:2:145:89:-407:36:328}
{fontsize=40}{bold}Astronomical Telescope{fontsize=20}
Two {link=1,converging lenses} can be used to construct an astronomical
telescope.
The first lens is used to create a real image of the object in between
the two lenses. The second lens then creates a virtual image of this image
at a comfortable distance from the eye.
The final virtual image is inverted with respect to the
object. This is unimportant in astronomy but would be confusing
for terrestrial use. That's why binoculars contain prisms to invert the image.
The earliest from of terrestrial telescope is called the {link=5,Gallilean telescope}.
It uses a diverging lens nearest the eye and a converging lens furthest from the eye.
Try moving the focus point of the right-hand lens so that it becomes a diverging
lens. Then move the lens so that the intermediate image is near the right-hand
focus point. You should be able to produce an upright virtual image of the object.
See also:\
{link=1,One Lens}\
{link=2,Two Lenses}\
{link=5,Gallilean Telescope}\
{link=3,Microscope}\
\end
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Microscope
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Topic Text -----------------------------
{keep}{embed=lens.dll,Lens,70:15:2:33:-222:-264:275:91}
{fontsize=40}{bold}Compound Microscope{fontsize=20}
The first lens (the objective lens) has a short focal length and
is used to create a real image of the object in between
the two lenses. The second lens (the eyepiece) then creates a virtual image of this image
at a comfortable distance from the eye.
The final virtual image is inverted with respect to the
object.
See also:\
{link=1,One Lens}\
{link=2,Two Lenses}\
{link=4,Telescope}\
{link=5,Gallilean Telescope}\
\end
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Two Lenses
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a
Topic Text -----------------------------
{keep}{embed=lens.dll,Lens,70:15:2:82:-164:-312:82:184}
{fontsize=40}{bold}Two Lenses{fontsize=20}
Two {link=1,converging lenses} can be used to construct a {link=4,telescope}
or a {link=3,microscope}.
In both cases, the first lens is used to create a real image of the object in between
the two lenses. The second lens then creates a virtual image of this image
at a comfortable distance from the eye.
In both instruments, the final virtual image is inverted with respect to the
object. A {link=5,Gallilean telescope} creates an upright virtual image. It uses
a diverging lens nearest the eye and a converging lens furthest from the eye.
See if you can make each of these instruments.
See also:\
{link=1,One Lens}\
{link=4,Telescope}\
{link=5,Gallilean Telescope}\
{link=3,Microscope}\
\end
1
One Lens
INDEX
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Topic Text -----------------------------
{keep}{embed=lens.dll,Lens,70:15:1:166:0:-298:0:0}
{fontsize=40}{bold}One Lens{fontsize=20}
A {bold}converging {bold}(convex) lens causes rays of light to converge more
after passing through it.
If the object ({bold}o{bold}) is further from the lens than the focal point ({bold}f{bold}) then
a real image ({bold}r{bold}) is formed on the opposite side of the lens.
If the object is nearer to the lens than the focal point then
an enlarged virtual image is formed on the same side of the lens.
That is how you use a lens as a simple microscope (a magnifying glass).
If the object is at the focal point then the image is at infinity.
Pick up the object, lens or focal point and try moving them around.
If you move the focal point to the other side of the lens then the lens becomes a
{bold}diverging {bold}(concave) lens.
A diverging lens causes rays of light to diverge more.
A a real object near a diverging lens always produces a virtual image on the
same side of the lens.
See also:\
{link=2,Two Lenses}\
\end