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Understanding Microscopes: Measurement Units, Types, and Limitations

This section explores the fundamental concepts of microscopy, including metric measurement units, such as meters, kilometers, centimeters, and nanometers. It discusses various types of microscopes—light and electron microscopes—including their functions, magnification capabilities, and resolutions needed to view microscopic details. Key distinctions between light and electron microscopes are highlighted, emphasizing their respective advantages and limitations in studying living cells and their imaging techniques, such as micrographs and various electron microscopy types.

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Understanding Microscopes: Measurement Units, Types, and Limitations

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  1. Chapter 3 Section 1 Microscopes

  2. Units of Measure • Metric system of measurement • International System of Measurement SI • Base Unit is the Meter (m) • Kilometer = 1,000 m (2/3 of a mile) • Centimeter = .01 m (1/2 diameter of penny) • Millimeter = .001 m (width of pencil tip) • Micrometer = .000001m (bacteria cell) • Nanometer = .000000001 m (water mol.)

  3. Light Microscopes • Light passes through one or more lenses to produce an enlarged image of a specimen

  4. Electron Microscopes • Forms an image of a specimen using a beam of electrons rather than light • 3 Types • Transmission electron microscopes (TEM) • Scanning electron microscope (SEM) • Scanning tunneling microscope

  5. Micrographs • The image produced by the microscope • Type of microscope • Magnification • Name of object • Light Microscope • 320 magnification • Amoeba

  6. Magnification & Resolution • Magnification • Makes the image appear larger than its actual size • Resolution • A measure of the clarity of an image • High magnification & good resolution are needed to view details of extremely small objects clearly.

  7. Limitations of Microscopes • Light microscopes: lower magnification power but can view LIVING cells • Electron microscopes: higher magnification but cannot view living cells

  8. Light Microscope • Ocular lens - closest to the eye • Objective lens - closest to the specimen • Both magnify • 40x objective & 10x ocular = 400x magnification

  9. Electron Microscopes • Can magnify 200,000x • Both electron beam and specimen must be placed in a vacuum chamber • Living cells cannot be viewed • 3 Types • Scanning Electron Microscopes (SEM) • Transmission Electron Microscopes (TEM) • Scanning Tunneling microscopes

  10. Scanning Electron Microscope • Specimen is coated with a thin layer of metal • 3-D image of cell surfaces • Black & white image that can be artificially colored

  11. Thin metal coating

  12. SEM of Human Blood

  13. Foot of a House Fly SEM x300

  14. Transmission Electron Microscope • Cross section of specimen • Non living • Stain with metal ions • Electrons pass through specimen & form image • Image is in black & white (Can be enhanced with color)

  15. Corona Virus (TEM)

  16. Cytoplasm of Liver Cell (TEM)

  17. Bacteriophages (TEM)

  18. Golgi Apparatus (TEM)

  19. Scanning Tunneling Microscope • 3D image of the specimen’s surface • Can be used on living organisms

  20. Scanning Tunneling Image

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