Microscope Parts and Function

• The compound microscope was invented around 1590 by Zacharias Janssen, a Dutch spectacle maker.
• Compound microscopes use lenses and light to enlarge images, also called optical or light microscopes.
• The simplest optical microscope is a magnifying glass, good for about 10X magnification.
• Compound microscopes use two systems of lenses for greater magnification: the ocular (eyepiece) lens and the objective lens.

Microscope Parts and Functions

• Eyepiece Lens: The lens you look through, usually 10X or 15X power.
• Tube: Connects the eyepiece to the objective lenses.
• Arm: Supports the tube and connects it to the base. Used to carry the microscope.
• Base: The bottom of the microscope, used for support.
• Illuminator: A steady light source (110 volts) used instead of a mirror.
• Stage: The flat platform where slides are placed.
• Stage Clips: Hold the slides in place on the stage.
• Revolving Nosepiece/Turret: Holds two or more objective lenses and rotates to change the power.
• Objective Lenses: Usually has 3 or 4 lenses (4X, 10X, 40X, 100X power).
• Total Magnification: Calculated by multiplying the eyepiece lens power by the objective lens power [(e.g., 10X eyepiece with 4X objective = 40X total magnification)].
• Objective Lens Length: Shorter lenses are lower power, longer lenses have greater power.
• Retractable High Power Objective Lenses: These lenses (e.g., 40XR) retract if they hit a slide, protecting the lens and the slide.
• Rack Stop: An adjustment that prevents the objective lens from getting too close to the slide, preventing damage.
• Diaphragm/Iris: A rotating disk under the stage with different sized holes and adjusts the intensity and cone of light projected into the slide.
• Diaphragm adjustment depends on the transparency of the specimen, desired contrast, and the objective lens in use.
• Coarse Adjustment: Used to initially focus the microscope, used only with the low power objective.
• Fine Adjustment: Used to focus the microscope, used with the high-power objective for fine-tuning the focus.

How to Focus Your Microscope:

• Start with the lowest power objective lens.
• From the side, lower the lens as close to the specimen as possible without touching it.
• Look through the eyepiece and focus upwards only until the image is sharp.
• Use the fine adjustment knob for minor adjustments with the next power lens.
• Keep both eyes open when viewing through the microscope to prevent eye fatigue.
• Remove eyeglasses to prevent scratching the lenses.

Wet-Mount Slide Procedure:

• Place a clean slide on a paper towel, handling it by the edges to avoid fingerprints.
• Place a drop of water on the center of the slide.
• Use tweezers to place the specimen in the drop.
• Hold the cover slip upright and carefully lower one edge next to the water.
• Allow the liquid to spread across the coverslip to minimize air bubbles.
• An absorbent towel can draw out excess water.
• Always use a coverslip to protect the objective lens from the liquid.

How To Stain a Slide:

• Place a drop of Methylene Blue stain on one edge of the coverslip.
• Place the flat edge of a paper towel on the opposite edge.
• The paper towel will draw the water and stain under the coverslip.
• Add more stain as needed and ensure the stain is covering the specimen.
• Wipe off excess stain to avoid staining the objective lenses.
• Wash and dry the slide and coverslip after use.
• Slides must be put away in the proper trays

General Microscope Care:

• Handle carefully, as microscopes are expensive to replace.
• Keep power cords and microscopes away from the counter edge.