|The image at the left is that of adissecting or stereo microscope. Notice that it has only two sets of lenses, including the eyepiece. The specimen to be observed is anopaque object (light does not pass through it). The observer sees the surface of the dissection specimen or other specimen being studied. This specimen is placed in a container on the stage of the microscope.
Biologists use the light microscope to observe microscopic specimens.
This microscope is also called the compound microscope is given its name because it has more than two sets of lenses.
It has an eyepiece lens (or ocular) and two or more sets of objective lenses (this microscope has three lenses) on a nosepiece that usually revolves.
This kind of microscope is also called a light microscope as it requires a source of light to pass through the specimen.
The specimen observed with this kind of microscope is usually microscopic and has to be translucent (allows light to pass through it).
The specimen to be observed is placed on the stage of this microscope.
|Parts of the Light Microscope
- eyepiece or ocular
- body tube
- fine adjustment knob
- high power objective
- low power objective
- mirror (many microscopes have a light instead)
- coarse adjustment
- stage clip
- inclination joint
Functions of the Light Microscope Parts
- eyepiece (ocular) – where you look through to see the image of your specimen.
- body tube-the long tube that holds the eyepiece and connects it to the objectives (not labeled)
- fine adjustment knob-small, round knob on the side of the microscope used to fine tune the focus of your specimen after using the coarse adjustment knob
- nosepiece-the rotating part of the microscope at the bottom of the body tube; it holds the objectives
- high power objective — used for high power magnification of the specimen (the longer objective lens)
- low power objective — used for low power magnification of the specimen
- diaphragm-controls the amount of light going through to the specimen
- light or mirror-source of light usually found near the base of the microscope; makes the specimen easier to see
- base-supports the microscope
- coarse adjustment knob — used for focusing on low power
- arm-part of the microscope that is grasped when one carries the microscope
- stage clips-shiny, clips on top of the stage which hold the slide in place
(The specimen is placed on the stage for viewing.)
- inclination joint -is used to tilt the microscope
Some Microscope Usage Rules
- Always carry the microscope with two hands – one on the arm and one underneath the base of the microscope. Hold it up so that it does not hit other objects.
- Do not touch the lenses. If they are dirty, ask the teacher for special lens paper or ask your teacher to clean the lenses for you.
- If using a microscope with a mirror, do not use direct sunlight as the light source. Blindness can result. If using a microscope with a light, turn off light when not in use.
- Notify teacher if a slide or cover slip breaks. Students should not handle broken glass.
- Always clean slides and microscope when finished. Store microscope set on the lowest power objective with the nosepiece turned down to its lowest position (using the coarse adjustment knob). Cover microscope with dust cover and return it to storage as directed by your teacher.
Other Points About the Compound Microscope
- Always begin focusing on the lowest possible power. Remember to center the specimen you
are observing in the field of view before switching to a higher power.
Make certain that you move the objectives away from the specimen when focusing so their is no collision between
the objective being used and the slide/cover slip which may damage the objective lens.2. As you switch from low to high power, the field of view becomes darker. To deal with this
the diaphragm needs to be opened to allow in more light. (Frequently on low power the
diaphragm needs to be partially closed as it is too bright.)3. As you switch from low to high power the field of view becomes smaller.
|Images viewed under the light microscope are reversed (backward) and inverted (upside down). This is a compound light microscope view of the letter F placed on a slide in its normal position.