PreLab 7 Using the Microscope DONE

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Lone Star College System, North Harris *

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1406

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Biology

Date

Jun 14, 2024

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pdf

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2

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PreLab 7: Using the Microscope 1 _______________________________________ . . . . . . . In Activity 1 of this lab, you will view a slide at 3 magnifications. A compound light microscope directs light through 2 lenses which affect magnification: the eyepiece lens and objective lens. The eyepiece lens alone magnifies 10X. The magnification of each objective lens is shown in parentheses below. What is total magnification for each? scanning (4x): ______ low power (10x): ______ high power (40x): ______ The 3 concentric circles to the right represent the relative size of the field of view at the 3 total magnifications above. Use red to trace over the line representing the field of view at scanning power, yellow for low power and blue for high power. Which objective would you use to see the entire Amoeba (pond water protist)? ________________ If you switched to low power for a better look at the cell’s nucleus, would it be visible in the low power field of view? _____ What would you need to do before switching objectives to make the nucleus visible at low power? ______________________ Assume that you are told to focus on a vacuole (white organelle on the cell above) at high power and capture an image. Considering the size of the fields of view illustrated above, why would you start your search for the vacuole at scanning power, not high power? ___________________________________________ Inversion is a property of a compound light microscope . How will the image you see through the microscope compare to the actual object being viewed? ___________________________________________ How will the direction of slide movement viewed through the microscope differ from the direction you are manually moving a slide? __________________________________________________ In Activity 1, you will also use a dissecting microscope. Which light, top or substage, should be used to view a penny? ______________________ In Activity 2, you will use the digital compound light microscope to take pictures. Once you have the image on the monitor, you will capture it, paste it in a Word doc and label it. How do you copy the image? _______________________________ Using the Microscope to Capture Digital Images 7 _____________________________________________________________________ . . . . . . . . PreLab 7 total magnification = X magnification of objective lens eyepiece magnification Name ______________________ Team # ___
2 PreLab 7: Using the Microscope The image to the right is of Entamoeba histolytica , the protist that causes amoebic dysentery. The parasite was viewed using the high power objective. Properly label the image in the space below it (see page 30). You will capture 4 images in this lab. List them below, along with the objective in use when capturing the image, and the total magnification. Slide # object objective total magnification 1 2 3 4 Compound Light Microscope Parts Read this description of the light microscope, then label each bolded part on the diagram. 1. A microscope is carried with one hand on the base and the other on the arm . 2. The stage is the black platform where a slide is placed for viewing. There is a glass condenser beneath the aperture (hole) in the stage . It channels light onto a specimen. 3. Attached to the stage is a mechanical stage apparatus that holds a slide in place. Two slide movement knobs (one beneath the other) allow the slide to be moved left, right, forward, or back. 4. Beneath the stage is the iris diaphragm . It controls the amount of light passing through a slide. There is also a light dimmer on the base to adjust light intensity. 5. The eyepieces are at the top of the body tube. The lenses within the eyepieces magnify10x. 6. The revolving nosepiece is at the lower end of the body tube. Attached to the revolving nosepiece are three objective lenses that differ in magnification. To change the lens being used, just turn the revolving nosepiece. 7. The microscope has coaxial focal adjustment knobs (one nested inside the other). These raise or lower the stage. The larger coarse adjustment knob moves the stage a visible distance and should be used for initial focusing. The smaller fine adjustment knob within it moves the stage much more slowly to allow fine focusing. Slide: _____________ ___________ (_____X)
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