The Microscope Packet #4 11/12/2018 3:25:39 AM11/12/2018 3:25:39 AM © Ryan Barrow 2012 © Ryan Barrow 2008

Historical Timeline 1609 – Galileo Galilei develops a compound microscope with a convex and a concave les. 1665 – Robert Hooke publishes Micrographia and coins the word cell for structures he discovers in cork bark 1674 – Anton van Leeuwenhoek improves on a simple microscope for viewing biological specimens 1931 – Ernst Ruska starts to build the first electron microscope 11/12/2018 3:25:39 AM11/12/2018 3:25:39 AM © Ryan Barrow 2012 © Ryan Barrow 2008

Types of Microscopes 11/12/2018 3:25:39 AM11/12/2018 3:25:39 AM © Ryan Barrow 2012 © Ryan Barrow 2008

Types of Microscopes I Compound Microscope Light microscope that has two converging lens systems: the objective and the eyepiece 11/12/2018 3:25:39 AM11/12/2018 3:25:39 AM © Ryan Barrow 2012 © Ryan Barrow 2008

Types of Microscopes II Electron Microscope Any class of microscopes that use electrons instead of light to form images of very small objects such as individual parts of small living things 11/12/2018 3:25:39 AM11/12/2018 3:25:39 AM © Ryan Barrow 2012 © Ryan Barrow 2008

Types of Microscopes III Transmission Electron Microscope Microscope used to reveal the internal structure of microbial and cell types. Scanning Electron Microscope The electron beam is scanned, or swept over a metal coating to form a three-dimensional image. Scanning Tunneling Microscope Can produce three-dimensional images of individual molecule and atoms, as well as movies Microscopes Compound Microscope Light Microscope Electron Microscope Transmission Electron Microscope Internal Structures Scanning Electron Microscope 3D image Scanning Tunneling Microscope Molecules & Atoms 11/12/2018 3:25:39 AM11/12/2018 3:25:39 AM © Ryan Barrow 2012 © Ryan Barrow 2008

The Compound Microscope 11/12/2018 3:25:39 AM11/12/2018 3:25:39 AM © Ryan Barrow 2012 © Ryan Barrow 2008

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The Compound Microscope Base Supporting structure that generally contains the source Condenser Converges light beams to pass through the specimen Iris Diaphragm Controls the amount of light passing through the specimen 11/12/2018 3:25:39 AM11/12/2018 3:25:39 AM © Ryan Barrow 2012 © Ryan Barrow 2008

Compound Microscope II Objective Lens Magnifies image Body Tube (Arm) Conveys light to the ocular lens Ocular Lens (Eye piece) Magnifies the image from the objective. A microscope with one ocular lens (eyepiece) is monocular; a microscope with two ocular lenses is binocular 11/12/2018 3:25:39 AM11/12/2018 3:25:39 AM © Ryan Barrow 2012 © Ryan Barrow 2008

Compound Microscope III Mechanical Stage Allows precise control in moving the slide Coarse Adjustment Knob used to locate specimen Fine Adjustment Knob used to bring the specimen into sharp focus 11/12/2018 3:25:39 AM11/12/2018 3:25:39 AM © Ryan Barrow 2012 © Ryan Barrow 2008

Compound Microscope IV Total magnification Calculated by multiplying the magnifying power of the objective lens by the magnifying power of the ocular lens. Increased magnification is no value unless good resolution can also be maintained. 11/12/2018 3:25:39 AM11/12/2018 3:25:39 AM © Ryan Barrow 2012 © Ryan Barrow 2008

The Behavior of Light Used for the Compound Microscope Properties of Light 11/12/2018 3:25:39 AM11/12/2018 3:25:39 AM © Ryan Barrow 2012 © Ryan Barrow 2008

Properties of Light Reflection Transmission Absorption Light strikes an object and bounces back Transmission Passage of light through an object Must be one of these 2 for a microscope Absorption Taken up by that object and used as energy Photosynthesis 11/12/2018 3:25:39 AM11/12/2018 3:25:39 AM © Ryan Barrow 2012 © Ryan Barrow 2008

Properties of Light II Refraction Bending of light as it passes through one medium to another of different density 11/12/2018 3:25:39 AM11/12/2018 3:25:39 AM © Ryan Barrow 2012 © Ryan Barrow 2008

Properties of Light II Diffraction Occurs when light rays are bent as they pass through a small opening, such as a hole, a slit, a space between two adjacent cellular structures, or a small, high powered, magnifying lens in a microscope. The bent light rays distort the image obtained and limit the usefulness of the light microscope. 11/12/2018 3:25:39 AM11/12/2018 3:25:39 AM © Ryan Barrow 2012 © Ryan Barrow 2008

Properties of Light Properties of Light Reflection Strikes & bounces back. Transmission Passes through an object. Absorption Absorbed by object. Refraction Bends passing from medium to medium. 11/12/2018 3:25:39 AM © Ryan Barrow 2012

Use of Immersion Oil With the Compound Microscope 11/12/2018 3:25:39 AM © Ryan Barrow 2012

Immersion Oil Immersion Oil Same index of refraction as glass Used to replace air to prevent refraction at a glass-air interface Works as a “secondary lens” Allows a clearer and larger image 11/12/2018 3:25:39 AM11/12/2018 3:25:39 AM © Ryan Barrow 2012 © Ryan Barrow 2008

Review 11/12/2018 3:25:39 AM © Ryan Barrow 2012

Review The Microscope Types of Microscopes Compound Electron Properties of Light Four Properties Use of Oil Immersion 11/12/2018 3:25:39 AM © Ryan Barrow 2012