Microscope Tutorial

Basic Properties of a Microscope All microscopes share basic properties Two-lens system (higher magnification) Light source that can be manipulated (visualization and contrast) Mechanical adjustable parts that can change the distance between lenses and specimen (focusing on something specific)

Components of the Microscope

Let’s Take It Step by Step Base and arm: we always transport the microscope using the base and the arm

Magnification Lenses Body tube separates eye and nosepieces Eyepiece contains the ocular lens Nosepiece contains objective lenses with magnification of 5x,10x,40x, 100x Body tube separates eye and nosepieces Total magnification = ocular x objective magnification

Lightsource: Visualization and Contrast Illuminator: a light source to view your specimen Abbe Condenser:  focuses light onto the specimen.  Most useful at the highest powers Iris Diaphragm:  regulates amount of light entering the lens system.  Its use depends on the transparency of the specimen, the degree of contrast you desire and the particular objective lens in use.

Finding Your Specimen Mechanical Stage: holds your slide in place Control Knobs: allows you to move the stage to view a particular portion of your slide

Focusing Your Specimen Coarse Adjustment Knob: initial adjustment; only use with scanning and 10x lenses only! Fine Adjustment Knob: use with 40x and 100x power

How to Focus Your Microscope Start with the lowest power objective lens first While looking from the side, crank the lens down as close to the specimen as possible without touching it Look through the eyepiece lens and focus upward only until the image is sharp Once the image is sharp with the low power lens, you should be able to simply click in the next power lens and use the fine focus adjustment

Special Terms Par focal: when one lens is in focus, other lenses will also have the same focal length (i.e. the other lenses should be in focus, too) Par centric: when the image is centered at one magnification, it will also be centered at higher magnifications

Resolving Power The ability of a lens to show two objects as separate entities Determined by the wavelength of light and the numerical aperture (also in part on the refractive index…the bending power of light passing through air from the glass slide to the objective lens)

Refractive Index Light bends when it passes through media of different densities At high magnifications, the light that passes through the slide will bend enough so it will not pass into the objective lens Loss of light affects resolution

Oil Immersion Provides the best resolution and magnification (1000x) Oil and glass have similar refractive indices, so light does not bend as it does when it hits air Oil allows light to reach objective lens and resolution is maintained at high magnification

Oil Immersion: Proper Technique Focus first on high power. Tweak your focus until it is perfect with the fine adjustment. Turn the revolving nosepiece until it is between the high and oil immersion lens, use oil dropper to place a drop over the center of the slide. Slowly turn lens into the oil. Then again use the fine adjustment to make the image clear.

Putting the Microscope Away Clean all lenses with dry, clean lens paper *Put scanning lens in place* *Lower and center the stage completely* Wipe oil off of lens Remove slide and wipe clean Turn light off Unplug and cover