Microscopes

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Microscopes
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Contents

• History
• Structure
• Uses
• Images

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History

• 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.

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The Father of Microscopy

• 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.

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Why do we need microscopes?

• Not everything we want to see is visible to the
  naked eye.
• Microscopes uses lenses to brighten and enlarge
  nearby and very small objects.

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Structure

• 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

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The Objective Lens

• 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)

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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
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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.

http//www.physics.carleton.ca/watson/1000_level/
Waves_and_Optics/Gifs/microscope_0.gif
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Illumination

• 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.

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There are four adjustments to be made when using
a microscope.

• 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.

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Uses

• 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

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A hydra getting ready for reproduction http//www.
microscope-microscope.org/microscope-images.htm
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A paramecium http//www.microscope-microscope.org/
gallery/Mark-Simmons/pages/paramecium2.htm
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A green protist http//www.microscope-microscope.o
rg/gallery/Mark-Simmons/pages/the_fish.htm