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Science 10

Science 10. Aim: To observe the developments of imaging and staining technologies. Agenda. Science Sizzler Reflection Test marks Microscope notes continued Electron microscope video.

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Science 10

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  1. Science 10 • Aim: To observe the developments of imaging and staining technologies

  2. Agenda • Science Sizzler • Reflection • Test marks • Microscope notes continued • Electron microscope video

  3. Contrast and Resolution are two important aspects that affect what you are looking at through a microscope. • Contrast is necessary in order to see detail. • Resolution is necessary to distinguish between two structures that are close together.

  4. Contrast • Most cells are colourless when light passes through them. • Scientists found that manipulating the light source could alter the contrast between the structures in the cell. • Experiments with stains showed that particular stains could improve contrast by attaching to parts of the cell.

  5. A potential downside to staining and fixing cells is that it kills the cell. • Therefore it is not possible to view a living cell.

  6. Resolution or Resolving power • Ability to distinguish between two structures that are very close together. • How clear an image is depends on the resolution of the image • The human eye can distinguish objects that are 0.1 mm or larger.

  7. Looking at anything that is smaller 1 half of the wavelength of light will be indistinguishable.

  8. Contrast Enhancing techniques • Done by altering the light path through a specimen. • Includes dark field, phase contrast, and differential interference.

  9. Fluorescent Microscopy • Fluorescent substances were attached to molecules in tissues • These tissues were subjected to ultra-violet light, and the fluorescent molecules would emit light.

  10. Confocal Technology • In confocal microscopes, a laser concentrates light onto a specimen. • Reflection is passed through a tiny opening called confocal pinhole and reaches an electron detector which converts the light to an image. • Can produce a 3D image by combining multiple images.

  11. Electron Microscopy • First EM developed in the 1930’s at the University of Toronto. • Uses a beam of electrons instead of light waves to provide images with more detail. • Creates images from the scattering or absorption of the electron beam by the specimen.

  12. Transmission Electron Microscope • Depends on a beam of electrons that pass through a very thin section of fixed and stained tissue embedded in plastic. • Black and white photos are produced. • Magnifies up to 1,500,000X and a resolution of about 2.5 nm

  13. Scanning Electron Microscope • Developed in the 1940’s • Gives images of the surface features of a specimen. • Specimens fixed and covered with eletcron-dense material like gold, which reflects electrons. • Electrons bounce of specimen, are picked up by sensor, and 3D images are formed.

  14. Operates up to a Magnification of 300,000x and has a resolution of 20 nm • Photos taken by both of these microscopes are called electron micrographs. • A difficulty of the TEM is that it is hard to create a 3D image from thin slices. • The specimens must also be fixed.

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