[BIO 11.1] E1 - Microscopy

• Objects smaller than 0.1 millimeters cannot be seen with the naked eye. Thus, we use optical instruments, one of which is the microscope.
• Light microscopy is a form of microscopy that uses light to illuminate a specimen, wherein the image of a dark specimen is set against a light background.
• Compound light microscopes use a two-lens system to obtain detailed images of tiny specimens.
• The base supports the entire microscope.
• The arm is the curved part of the microscope that holds the two-lens system.
• The pillar is the base's extension, connecting the base and arm.
• The inclination joint, found only in the traditional microscope, connects the pillar and arm. It can be bent to tilt the upper part of the microscope.
• The stage is at the base of the arm, where the specimen is supposed to rest.
• The stage clips are used to keep the specimen in place.
• The stage control knob moves the stage around.
• In traditional microscopes, the coarse and fine adjustment knobs control the body tube. In electronic microscopes, they control the stage height.
• The eyepiece or ocular is where one views the specimen. It is the first lens in the two-lens system and is an example of concave lens.
• The draw tube carries the ocular in traditional microscopes.
• The body tube carries the draw tube in traditional microscopes or the ocular in electronic microscopes. Light is reflected from the objectives into the body tube to the eyepiece.
• The revolving nosepiece is used to change between objectives.
• The objectives directly observe the specimen. It is the second lens in the two-lens system and is an example of convex lens.
• The scanning objective has a magnification of 4x, a numerical aperture of 0.10, and a red ring.
• The low-power objective has a magnification of 10x, a numerical aperture of 0.25, and a yellow ring.
• The high-power objective has a magnification of 40x, a numerical aperture of 0.65, and a blue ring.
• The oil immersion objective has a magnification of 100x, a numerical aperture of 1.25, and a white ring.
• The substage is directly below the stage, consisting of the condenser and iris diaphragm.
• The condenser, found below the stage, focuses or condenses light into the specimen.
• The iris diaphragm, found below the condenser, regulates the amount of light passing into the condenser.
• The substage control knob controls the height of the substage.
• There are two types of compound light microscopes: traditional and electronic.
• The lamp or illuminator acts as the light source for electronic microscopes.
• The light control knob controls the amount of light emitted by the lamp.
• The mirror reflects light from external sources in traditional microscopes.
• In retrieving the microscope:

  1.) Hold the arm with one hand, and support the base with the other hand.

  2.) Do not carry anything else, and hold the microscope upright.

  3.) Lay it on the table at least 3 cm from the edge.

  4.) Inspect the microscope for any damaged or missing parts.
• In using the microscope’s knobs, remember to use both the left and right knobs at once to ensure they don’t loosen.
• Because the image projected in the microscope is inverted, mirrored, magnified, and virtual, moving the stage makes the image move in the opposite direction.
• Closing the iris diaphragm decreases the light, leading to greater contrast and thus a crisper image.
• A microscope is parcentric when the image remains centered even when the magnification changes.
• A microscope is parfocal when the image remains focused when changing magnification.
• Higher objectives lead to the decreased viewable area of the specimen as it is more zoomed in.
• Higher objectives lead to decreased brightness on the image, as less light is projected into the eyepiece.
• In returning the microscope:

  1.) Set the stage and substage to their lowest points, and set the revolving nosepiece to the lowest objective.

  2.) In traditional microscopes, set the mirror to a vertical position facing sideways.

  3.) In electronic microscopes, set the light control knob to the lowest level and turn the power off. Wrap the power cord properly around the microscope.

  4.) Hold it the same way you would when retrieving the microscope, and return it to where it was obtained.
• Remember to rotate objectives with your fingers on the revolving nosepiece, not the objectives.
• Given a magnification of magnitude n:

  -nx refers to the magnification of the microscope

  -xn refers to the magnification experienced by the specimen
• Microscope eyepieces can be of varying eyepiece magnification. The laboratory microscopes have a magnification of 10x.