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MICROSCOPES - PowerPoint PPT Presentation

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MICROSCOPES

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  1. MICROSCOPES

  2. The microscope is an instrument that allows us to see objects that are normally too small for the eye to see • It was invented by Anton VanLeewenhoek in the 1600’s • Robert Hooke was the 1st to see cells

  3. Types of Microscopes Simple Microscope – a single lens (eg. magnifying glass)

  4. 2. Compound Light Microscope – light is projected through 2 lenses to view an “image” of an object. The image is somewhat blurry. BEST FOR VIEWING LIVE SPECIMENS pg. 16 – Human Cheek Cells - cell organelles stained green and nuclei yellow pg. 29 – Egg Cell – surrounded by smaller cells that support and nourish egg

  5. 3. Electron Microscope – uses a beam of electrons to take a magnified ‘picture’ of an object. eg. T.E.M. – Transmission Electron Microscope • designed by James Hillier • to view specimen, it is encased in plastic and shaved into very thin layers, allowing electrons to pass through it, therefore can only be used to view dead cells pg. 19 – goblet cell pg. 37 - lysosome

  6. eg. S.E.M. – Scanning Electron Microscope • reflects electrons from the surface of the specimen, allowing thicker specimens to be used The electron microscope can magnify objects to a very large size. The picture of the object is very clear. pg. 21 – RBC pg. 27 – Sperm Cells pg. 148 -RBC & capillary

  7. Important Vocabulary Magnification – apparent enlargement of an object - a magnification of 100X means that the object is 100 times bigger than the actual object Resolution – clarity, sharpness - the ability of a microscope to show two very close points

  8. Characteristics of a Compound Light Microscope When you go from low to medium to high power the: •light gets dimmer • field of view gets smaller • image gets bigger 2. The ‘image’ of an object under the microscope appears “backwards” For our school microscopes to calculate total magnification: Total Mag: objective power x ocular lens (10X) Low Mag : 4 X 10 = 40X Med Mag: 10 X 10 = 100X High Mag: 40 X 10 = 400X

  9. The Diameter of the Field of View Converting mm --- µm Sample Calculation: 4 mm = 1 mm = µm 1 mm = µm

  10. Activity Estimation of Specimen Size – handout Using prepared slides, Letter e, HYDRA and Volvox, sketch and estimate actual size Diagram - diagram is done in pencil - sketch (stipple) diagram on left side of blank paper & labels on right - diagram needs a title - include total magnification