Microscopes

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Microscopes
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What is a Microscope?

• A device for forming a magnified image of a small
  object.
• An optical instrument used for producing a
  magnified image of a small object.
• A device that allows a small object to be viewed
  under high magnification.

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Did You Know . . . ?

• The microscope is the most important tool for
  biologists.
• The first cells were seen in 1663.
• The first microscope was made in 1595.

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The Beginnings

• Of the five senses, the most important is sight.
• Aids in the process of gathering information
  about the environment that we are part of.
  However, this is adequate only to a certain
  point.
• Beyond this point, the human unaided eye fails to
  help us the amount of detail that it can provide
  is severely limited.
• In order to overcome those limitations, humans
  started to develop instruments like the
  magnifying glass, the spectacles, the telescope
  and the microscope.

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Founding Fathers of Microscopy

• Hans and Zacharias Janssen
• Robert Hooke
• Anton von Leeuwenhoek

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Hans and Zacharias Janssen

• Credit for the first microscope is usually given
  to Zacharias Janssen, around the year 1595.
• Since Zacharias was very young at that time, it's
  possible that his father Hans made the first one,
  but young Zach took over the production.
• The first compound microscopes produced by the
  Janssen's was simply a tube with lenses at each
  end.
• The magnification of these early scopes ranged
  from 3X to 9X, depending on the size of the
  diaphragm openings.

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Robert Hooke

• Hookes remarkable engineering abilities enabled
  him to invent and improve many mechanical
  devices, including timepieces and the Gregorian
  telescope.
• Hooke improved on early compound microscopes
  around 1660.
• In 1665, he coined the word cell to describe the
  features of plant tissue (cork from bark of an
  oak tree).

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Anton von Leeuwenhoek

• Leeuwenhoek was a man with many talents his most
  important attributes were creativity, power of
  observation, and ingenuity.
• He made simple (one lens) microscopes.
• He built the best microscopes for the time
  period.
• He was the first person to describe bacteria
  (from teeth scrapings) and protozoan (from pond
  water).

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Compound Light Microscope

• Compound
• Deals with the microscope having more than one
  lens.
• Light
• Refers to the method by which light transmits the
  image to your eye.
• Microscope
• Micro small
• Scope view

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Terminology

• Objective
• Ocular
• Total magnification
• Resolution
• Focal Point

• Lens closest to the specimen.
• Lens you look through.
• The total power of the microscope (multiply the
  magnification of both lenses).
• The amount of detail you can see in an image.
• The point at which the light from a lens comes
  together.

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How Does it Work?

• Microscopes take an image of something generally
  too small to see with the naked eye and magnify
  that image so that the observer can see it in
  greater detail.
• To magnify images, a microscope uses several
  lenses to change the angle at which rays of light
  strike the eye of the observer.

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Parts of the Microscope
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Ocular Lens or Eyepiece

• This lens sits directly in front of the
  observer's eye and does not typically change in
  magnification power.
• Older-style microscopes were "monocular," meaning
  they had only one eyepiece, but in recent years
  microscopes have been made "binocular" in order
  to relieve eyestrain and allow for more natural
  viewing.

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Objectives

• The objective lenses combine with the power of
  the ocular lens to create the magnified image.
• Frequently one starts on the lowest magnification
  to find focus and then increases magnification
  one objective at a time.
• This is facilitated by a rotating nosepiece that
  allows the objectives to be interchanged
  smoothly.

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Objective Lens

• Objective lenses come in several varieties.
• In a light microscope, the lowest power objective
  (frequently 4x or 10x) is referred to as the
  "scanning" objective, as it allows the observer
  to find an area of interest before increasing
  magnification.
• As magnification increases, the amount of light
  collected from the sample decreases. For this
  reason, the highest objective on a light
  microscope (such as the 100x) requires mineral
  oil to be applied to the gap between lens and
  sample. The oil has a greater refractive index
  and bends more light into the objective.

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Coarse Adjustment Knob

• Both knobs change the distance between objective
  and viewing sample.
• The coarse adjustment knob is primarily used with
  the scanning objective.
• It allows the user to bring the scope into
  approximately the right plane of focus.
• Once this has occurred, it is preferential to
  leave the coarse adjustment alone and use only
  the fine adjustment.

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Fine Adjustment Knob

• The fine adjustment knob helps clarify a
  partially focused image.
• It requires many more turns than the course
  adjustment to do the same amount of work.
• This allows the observer to take great care in
  clarifying the image.

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Stage

• The stage, usually adorned with stage clips of
  some sort, is where the specimen rests.
• After being centered over a hole in the middle
  and secured with the clips, the subject can be
  raised or lowered by the course and fine
  adjustment knobs.
• Also, the stage has its own controls for moving
  the subject left, right, back, and forward on the
  horizontal plane.

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Light Source

• The light source sits at the base of the
  microscope (usually) and either consists of a
  radiant bulb or a mirror for redirecting light.
• Light is shined up through the hole in the stage
  to illuminate the sample.

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Diaphragm

• Before the light enters the stage opening, it
  passes through the diaphragm.
• The diaphragm, which has an opening or "aperture"
  in the form of an iris, only allows light to pass
  through its center.
• By increasing or shrinking the size of the iris,
  you can control how much light passes through to
  the sample.
• The light is condensed in order to create the
  highest level of clarity to an image.

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The Body - Base Arm

• The "body" of the microscope is divided into two
  parts the base and the arm.
• The base is heavy and prevents the scope from
  slipping on the bench top or tipping over.
• The arm holds all of the apparatus in place above
  the light source.
• A microscope should ALWAYS be carried by both the
  base and the arm.

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Microscope Care Handling

• Transporting
• Handling
• Cleaning
• Storage

• Grab the arm with one hand and place your other
  hand on the bottom of the base.
• Never touch the lens with your fingers.
• Only use lens paper to clean the glass.
• Put the low power objective in place and the
  stage all the way up.

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Using the Microscope Before You Start

• Place the microscope on a table with the arm
  towards you about a fists length from the edge
  of the table.
• The microscope should be on the lowest power
  objective and the stage should be all the way up.
• The diaphragm should be set on the brightest
  field of view.

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Using the Microscope First Focusing

• Place a slide on the stage centering the specimen
  over the stage opening.
• Use the stage clips to hold the slide in place.
• Looking through the eyepiece, slowly turn the
  coarse adjustment knob until the specimen comes
  into focus.

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Using the Microscope Switching Objectives

• Look at the microscope from the side.
• Carefully revolve the nosepiece until the
  high-power objective lens clicks into place.
• Make sure the lens does not hit the slide.
• Looking through the eyepiece, use the fine
  adjustment knob until the specimen comes into
  focus.

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Cool Microscopic Images
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Cool Microscopic Images
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Cool Microscopic Images
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The Magnificent Microscope