Chapter 3_LAB 2 - Chapter 3/Exercise 2 CLASS NOTES Ar t...

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Chapter 3/Exercise 2 CLASS NOTES: Artifact: something that appears due to a mistake or imperfection; doesn’t correspond with the components of the object 4 important properties of a microscope: o Magnification (Length of image/Length of object) o Resolving Power = Resolution The closest that 2 edges can be together and still be distinguished as separate entities Due to the electromagnetic spectrum(visible light) = 380nm to 750nm The vibrations of light create the fuzziness Maximum RP = ½ of light used to view the image λ 560/2 (avg. of all light) A smaller will produce a better resolving power λ o Aberrations (discussed below) o Contrast: measure of the ability to view an image distinctly from its surroundings when it is sufficiently large to observe and is resolved from its surroundings Intensity contrast and color contrast Animal cells do not have much color, therefore less contrast than plants To improve contrast: change specimen by dying it or staining it (stain binds to DNA) o A vital stain or dye does not kill the cell change how microscope interacts with light by changing the optics so that it enhances contrast o light passed through object bends differently; take advantage of this to enhance quality Modifying Light source to improve quality of image: o Monochromatic light and ultraviolet light (shorter ) λ SET OF PROCEDURES TO PREPARE A TISSUE SAMPLE:
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1. FIX the tissue; keep it in the same position (i.e.: wax) a. Chemically cross-links various components together b. Immediately kills the cells 2. D EHYDRATE : Replace H 2 O with organic material (ex: melted wax) by soaking it sequentially in solutions of water and organic solvent, eventually soak it only in organic solvent 3. EMBED : put material around and inside the cell a. Placed in a transparent material which dissolves in dehydration solvent b. Warm paraffin works well for tissues dehydrated with ethyl alcohol
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Chapter 3_LAB 2 - Chapter 3/Exercise 2 CLASS NOTES Ar t...

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