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Chapter 3

Chapter 3. Microscopes. Essential Questions. What is the difference between a light microscope & an electron microscope? Know what each type would be used for. What is proper care and use of the microscope? . Microscope Men of History.

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Chapter 3

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  1. Chapter 3 Microscopes

  2. Essential Questions • What is the difference between a light microscope & an electron microscope? • Know what each type would be used for. • What is proper care and use of the microscope?

  3. Microscope Men of History • 1665: Robert Hooke looked at a sliver of cork under a microscope and noticed some “pores” or “cells” in it. Coined the term cell. • 1674: Anton van Leeuwenhoek built a simple microscope with one lens to look at blood, yeast, and bacteria cells. First to see living things under the microscope, animalcules.

  4. Microscope Parts Eyepiece Revolving Nosepiece Arm Objective Lenses Stage Clips Coarse Adjustment Stage Diaphragm Fine Adjustment Light Source Base

  5. Microscope Care • Always use two hands to carry the scope, one on the arm, one on the base. • The stage should be placed all the way down, an objective lens placed on scanning power (red) when putting away. • Make sure to wrap up the cord and place the cover over the top of the microscope when finished. • Always grab appropriate microscope for the station you are at, and put away in appropriate spot in cabinet. • Lens paper is the only tissue that can be used when cleaning the eyepiece.

  6. How To Use The Microscope • Place the slide under the stage clips on the microscope, with the image in the center of the viewing field. • Start with the microscope on the scanning power (red). • Look into the eyepiece and use the coarse adjustment to focus the image so it is clear. • Adjust nosepiece to low power (yellow), and again use the coarse adjustment to focus the image. • Adjust nosepiece to high power (blue), and this time use the fine focus to adjustment to focus the image. * If image appears to dark or too light, use the diaphragm to adjust the amount of light that passes through the image.

  7. Use pencil, and take your time. All drawings should be drawn as seen. If in color, draw in color. Also draw to scale. The circle represents the field of view, if your specimen takes up the whole view, make sure your drawing reflects that. All drawings should include clear and proper labels, specimen name, and magnification. Example: Amoeba 400x Drawing Specimens

  8. Microscope Terms to Know • Magnification: ability to make an object appear larger • The objective lenses are used to increase magnification. • The Light microscope has 3 magnifications: Scanning, Low and High. Each objective will have its own magnification. In addition to this, the ocular lens (eyepiece) has a magnification. • The total magnification is the ocular x objective • Example: Low Power = 10x and Eyepiece is 10x, total magnification = 10 x 10 = 100x

  9. Terms cont. • Resolution: ability to make an object appear more clear • To increase resolution the fine and coarse adjustment is used.

  10. Microscope Types • Light Microscope: the models found in most schools, use compound lenses and light to magnify objects. The lenses bend or refract the light, which makes the object beneath them appear closer.

  11. Stereoscope • This microscope allows for binocular (two eyes) viewing of larger specimens. (The spinning microscope at the top of this page is a stereoscope) • Used in dissections

  12. Scanning Electron Microscope • Allow scientists to view a universe too small to be seen with a light microscope. SEM’s don’t use light waves; they use electrons (negatively charged electrical particles) to magnify objects up to two million times.

  13. Transmission Electron Microscope • Also uses electrons, but instead of scanning the surface (as with SEM's) electrons are passed through very thin specimens.

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