Transcript Microscopes

Microscopes
Contents

History
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Structure
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Uses
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Images
History
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Invented during the
Renaissance
Lenses had been used to
magnify images during the
first century A.D., but it was
not until the late 1500
hundreds when two Dutch
spectacle makers started
experimenting with several
lenses in a long tube.
The Father of Microscopy
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Anton van Leeuwenhoek (1632 – 1723)
 he
taught himself new methods for grinding
and polishing tiny lenses of large curvature
 these magnifications of up to 270 diameters
 he was the first to see and describe bacteria,
yeast plants and the circulation of blood
corpuscles in capillaries.
Why do we need microscopes?
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Not everything we want to see is visible to
the naked eye.
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Microscopes uses lenses to brighten and
enlarge nearby and very small objects.
Structure
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Microscopes are almost identical to Keplerian
telescopes, except for their objective lenses.
Microscopes uses a short focal length objective
lens to project a large real image of a nearby
object
They must gather large amounts of light from a
small object using an Objective Lens
The Objective Lens
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The microscope objective lens must be very
small and spherical, with a short focal length.
It must be able to:
 move in close to the object
 catch its rapidly diverging light
rays
 make those rays converge together as a real image
far from the lens
 the number marked on the side of the objective lens
will tell you how much the image is magnified (for
example: x40)
The Objective Lens
The Objective lens is usually a compound
lens, or a combination of two lenses made
from different types of glass.
 The second lens is really there to correct
any distortions caused by the first lens,
such as chromatic abberation.
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http://www.yesmag.bc.ca/how_work/microscope.html
The Eyepiece
The eyepiece is the second lens in a
microscope.
 It is used to magnify the object so it easy
to view with your eyes.
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http://www.physics.carleton.ca/~watson/1000_level/Waves_and_Optics/Gifs/microscope_0.gif
Illumination
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Illumination is very important in a
microscope.
 You
can shine a light upward THROUGH the
object – which lets you see how much light is
absorbed in different places.
 You can shine a light downward ONTO the
object – which lets you see how light reflects
from the surface.
There are four adjustments to be
made when using a microscope.
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Brightness – adjusts how light or dark the image is using
the illumination.
Focus – adjusts if the image is blurry or well defined by
using the focus knobs, which change the location of the
focal point.
Resolution – defines how easily you can define two
adjacent objects from each other and is adjusted by the
aperture of the objective lens
Contrast – which is the difference in lighting between two
areas. This can be adjusted by changing the intensity of
the light and the pinhole aperature.
Uses
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Microscopes have been and are being
used in many different areas, such as:
 identifying
minerals
 solving crimes
 see how freezing affects food
 study human cells
 find the cause of diseases
 discovering where illegal drugs are grown
A hydra getting ready for reproduction
http://www.microscope-microscope.org/microscope-images.htm
A paramecium
http://www.microscope-microscope.org/gallery/Mark-Simmons/pages/paramecium2.htm
A green protist
http://www.microscope-microscope.org/gallery/Mark-Simmons/pages/the_fish.htm