ACTIVITY 1A: MICROSCOPE

• Microscope:

  • Basic instrument in biology that enables students to observe enlarged images of tiny objects
• Eyepiece:

  • Also known as the ocular
  • lens which we look through in order to see the specimen being viewed
  • Has an initial magnification of 10x
• Revolving Nosepiece:

  • holds the four objective lenses
• The lower the magnification, the shorter the objective lens and the farther it is positioned from the specimen when focused.
• The scanning lens is a short lens which magnifies the size of an object 4x. It has the broadest field of view and is used for initial focusing.
• The low-power objective magnifies by 10x.
• The high-power objective magnifies by 40x. It is much longer than the first two.
• The longest is the one with 100x magnification. This is the oil immersion objective (OIO).
• The stage is the flat surface with the round opening in the center. The mechanical stage allows the slide to be manipulated by means of the mechanical knobs.
• Some microscopes do not have a mechanical stage, and stage clips are used to fasten the slides on the stage.
• The substage condenser is a lens located under the stage aperture, and its distance from the stage is controlled by a knob. Its function is to condense the light and focus it on the specimen.
• The iris diaphragm is beneath the condenser and functions to control the amount of light passing through the specimen. This can be moved from side to side to affect a change in light intensity.
• The substage illuminator is the source of light which illuminates the object being viewed. This may be replaced by a mirror.
• The illuminator control knob, located on the side of the base just below the mechanical stage adjustment knobs, controls the light output of the illuminator.
• The adjustment knobs are located on both sides of the microscopes, just above the base. There are two of these, one located outside the other.
• The coarse adjustment knob is the bigger of the two. Its function is to focus using the scanning and low power objectives.
• The fine adjustment knob is used in focusing at the high-power and oil-immersion objectives.
• A feature of a good microscope is its parfocal capability. This means that when a specimen is in focus under low-power magnification, one can switch to high-power magnification and have the specimen remain in fairly good focus.
• The dissecting microscope is useful when magnifications between 5x and 50x are desired. It is useful for viewing entire specimens of small animals or body parts of larger animals. It has the added advantage of giving a three-dimensional view of the object.