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An Introduction to the Microscope

An Introduction to the Microscope. Section 2.2. Magnifying Cells. To see most cells, you need to use a microscope. A microscope has one or more lenses that enlarge the image of an object as though you are walking closer to it. Early Microscopes.

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An Introduction to the Microscope

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  1. An Introduction to the Microscope Section 2.2

  2. Magnifying Cells • To see most cells, you need to use a microscope. • A microscope has one or more lenses that enlarge the image of an object as though you are walking closer to it.

  3. Early Microscopes • In the late 1500s, the first microscope was made by a Dutch maker of reading glasses. • In the mid 1600s, Antonie van Leeuwenhoek, a Dutch fabric merchant, made a simple microscope with a tiny glass bead for a lens.

  4. Early Microscopes • His microscope could magnify up to 270 times. • Today you would say his lens had a power of 270.

  5. Modern Microscopes • Depending on how many lenses a microscope contains, it is called simple or compound. • A simple microscope is similar to a magnifying lens. • It has only one lens. A microscope’s lens makes an enlarged image of an object and directs light toward your eye. • The change in apparent size produced by a microscope is called magnification.

  6. Modern Microscopes • The compound light microscope has two sets of lenses—eyepiecelenses and objective lenses. • The eyepiece lenses are mounted in one or two tubelike structures. • Compound light microscopes usually have two to four movable objective lenses.

  7. Magnification • The powers of the eyepiece and objective lenses determine the total magnifications of a microscope. • If the eyepiece lens has a power of 10 and the objective lens has a power of 43, then the total magnification is 430 (10 times 43).

  8. Light Microscope

  9. Electron Microscopes • Things that are too small to be seen with other microscopes can be viewed with an electron microscope. • Instead of using lenses to direct beams of light, an electron microscope uses a magnetic field in a vacuum to direct beams of electrons.

  10. Electron Microscopes • Scanning electron microscopes (SEM) produce a realistic, three-dimensional image. • Only the surface of the specimen can be observed using an SEM.

  11. Electron Microscopes • Transmission electron microscopes (TEM) produce a two-dimensional image of a thinly-sliced specimen. • Scanning tunneling microscopes (STM) are able to show the arrangement of atoms on the surface of a molecule.

  12. Cell Theory: A reason why we use microscopes • Cells weren’t discovered until the microscope was improved. • In 1665, Robert Hooke cut a thin slice of cork and looked at it under his microscope. • To Hooke, the cork seemed to be made up of empty little boxes, which he named cells.

  13. Cell Theory • In the 1830s, Matthias Schleiden used a microscope to study plants and concluded that all plants are made of cells. • Theodor Schwann, after observing different animal cells, concluded that all animals are made up of cells. • Eventually, they combined their ideas and became convinced that all living things are made of cells.

  14. Cell Theory • Several years later, Rudolph Virchow hypothesized that cells divide to form new cells. • His observations and conclusions and those of others are summarized in the cell theory.

  15. Question 1 Who developed a microscope using a tiny glass bead for a lens? A. Antonie van Leeuwenhoek B. Edward Jenner C. Matthias Schleiden D. Theodor Schwann

  16. Question 2 How many lenses does a simple microscope have? A. 0 B. 1 C. 2 D. 4

  17. Question 3 The conclusions listed in this table are known as the _______.

  18. A. Cell Theory B. Koch’s Rules C. Law of Independent Assortment D. Principles of Natural Selection

  19. Question 4 A microscope with one lens is called a ____. A. compound B. concave C. simple D. systemic

  20. Question 5 _________ is the change in apparent size produced by a microscope. A. Objective B. Eyepiece C. Magnification D. Membrane

  21. Question 6 To view extremely small cells organisms, which might you use? A. Magnifying Lens B. Objective Lens C. Concave Lens D. Electron Microscope

  22. Question 7 Which of these scientists was NOT involved with the discoveries of cells? A. Virchow B. Hooke C. Schwann D. Sagan

  23. Question 8 If a microscope has an eyepiece lens with a power of 25X and an objective lens with a power of 50X, what is the microscope's total magnification power? A. 2X B. 1250X C. 25X D. 75X

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