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Microscopy

Microscopy. Microscopes. There are different kinds of microscopes: the light microscope the electron microscope. Resolution and Magnification. The amount of detail in an object that can be seen is called “resolution”. Examine the four pictures of the fly’s head.

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Microscopy

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  1. Microscopy

  2. Microscopes • There are different kinds of microscopes: • the light microscope • the electron microscope

  3. Resolution and Magnification • The amount of detail in an object that can be seen is called “resolution”. • Examine the four pictures of the fly’s head. • A magnification increases, more of the detail of the head appears. • More magnification doesn’t always mean more resolution. Think of optical vs. digital zoom on your digital camera. • Microscopes are only useful if the they increase both magnification AND resolution.

  4. Light Microscopes Light microscopes use light rays which are focused with lenses. A stereo microscope uses low magnification to observe surfaces of a specimen. You will use a compound light microscope. It is used to observe thin, transparent specimens.

  5. Light Microscopes • They can magnify up to 1600X. • Magnifications higher than this are possible but not useful. Light waves bend around objects that are close together. Light waves are an average of 500 nm. • Therefore, it is difficulty to resolve objects that are closer together than 500 nm.

  6. Refraction Short wavelengths are “bent” more than long wavelengths dispersion Light is “bent” and the resultant colors separate (dispersion). Red is least refracted, violet most refracted. Courtesy of Dr. J. Paul Robinson, Purdue University Cytometry Laboratories

  7. Refraction He sees the fish here…. But it is really here!! Courtesy of Dr. J. Paul Robinson, Purdue University Cytometry Laboratories

  8. Try this at home!

  9. Label your microscope!

  10. Electron microscopes • Electron microscopes do not use light. They use electrons! • We will look at scanning electron microscopes (SEM) and transmission electron microscopes (TEM).

  11. Transmission Electron Microscopes (TEM) • Invented in 1933. They have improved a lot since then. • A very thin slice of the material to be tested is exposed to a beam of electrons. • A beam of electrons are shot through the specimen as well as through a series of circular magnetic lenses. • The electron beam then hits a fluorescent screen where an image is produced.

  12. Compare the light microscope with the TEM…

  13. A Transmission Electron Microscope

  14. Scanning Electron Microscopes (SEM) • Used to view the surface of a specimen. • Electrons are emitted from an electron gun. These are primary electrons. • The primary electrons cause secondary electrons to be released from the surface of the specimen which are picked up to construct an image.

  15. A Scanning Electron Microscope

  16. Micrographs • Definition: Micrographs are photos taken of objects under a microscope.

  17. Micrographs from compound light microscopes….

  18. These are cells scraped from the inside of a person’s cheek. Can you see the nuclei in each cell?

  19. The ‘holes’ are called stomata. The surface of an Iris leaf.

  20. Hydra under low power • Note the new hydra budding off the adult.

  21. Paramecium • A fresh water unicellular organism.

  22. What kind of cells are these? • Red Blood Cells (high power)

  23. Micrographs from electron microscopes….

  24. Do you know what this is? It’s pine wood. TEM or SEM? (SEM)

  25. Spermatozoopis • It lives in fresh water. • TEM or SEM? • (TEM)

  26. This is a cross section through a mature sperm cell, or spermatozoon, from C. elegans… • TEM or SEM? • (TEM)

  27. This micrograph shows the surface features of a mature sperm cell, or spermatozoon, from C. elegans . C. elegans is a worm… • TEM or SEM? • (SEM)

  28. It’s a hypodermic needle! SEM or TEM? (SEM) What the heck is this?

  29. Paramecium • SEM or TEM? • (SEM)

  30. Phagocyte eating bacteria • This phagocyte (White Blood Cell) is eating some Staphylococci bacteria (causes infections). • TEM or SEM? • (SEM)

  31. Endoplasmic Reticulum • TEM or SEM? • (TEM)

  32. Human hair • TEM or SEM? • (SEM)

  33. Cancer cell • Red Blood Cell • SEM or TEM? • (SEM)

  34. Binary Fission! • The final phase of division of the bacterium E. Coli • SEM or TEM? • (SEM)

  35. Microvilli • These extensions of a cell membrane help increase surface area for absorption. • SEM or TEM? • (TEM)

  36. E. Coli • A transmission electron micrograph of Escherichia coli (E.coli). (Image -- New York State Department of Health) • SEM or TEM? • (TEM)

  37. Papillomavirus FYI: Certain types of Papillomavirus can cause genital warts…

  38. The End

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