How Student Microscopes Work
All About Microscopes
Compound Light Microscope
Student microscopes are optical tools that are used by students and scientists to get a magnified view of very small objects or details. There are several types of microscopes, however, for students the most commonly used type is a basic compound light microscope. This type of microscope is call “compound” because it utilizes two lenses to magnify the objects on a slide. A compound light microscope is appropriate for examining cells, organisms and inorganic materials.
How It Works
Many science fair projects require the use of a compound microscope. A compound light microscopes work by shining a light through a condenser lens which is placed between the light source and the specimen tray. The image is then transmitted through the body tube and through the projector lens and finally to the eyepiece. As the image passes through each lens it is magnified by a specific ratio, usually 5, 10 or 15X.
To use a microscope you first prepare a slide, which is a small glass plate. To prepare a slide you will place a drop of water in the center of the slide and then add the cell or organism to be viewed in the water drop. You will then use a thin piece of glass or plastic to press down the specimen and keep it in the center of your slide.
Next you will place the slide under the slide clips, which are found on the stage of the microscope. This will secure your slide. Make sure that your specimen is positioned directly over the aperture.
Now you will turn on your light source and select the objective lens that you want. Make sure your body tube is high enough so that the objective lens that you select doesn’t crack or come into contact with your slide. Utilize your coarse and fine adjuster knobs to bring your specimen image into focus.
Oil Immersion Lens
Another option that you have for bringing out fine details in an organism or specimen is to use the oil immersion lens process. In this process you will create a wet mount slide like you did before. Then you will move the objective lenses so that no lens is snapped into position. Next you will place a small drop of oil on top of the cover slip. Then you will snap the 100X objective lens into place, which will bring it into contact with the oil. Use the fine adjuster knob to bring the objective lens up about 1mm from the slide cover slip. Next continue to adjust the fine adjuster knob until your image has been brought into focus.
How To Focus a Light Micrscope
Parts of a Microscope
Arm: The arm of the microscope is the metal or plastic handle shaped protrusion that connects the nose pieces/body tube configuration and it also acts as the carrying handle for the microscope.
Body Tube: The body tube is the container that houses the objective lenses which magnify the specimen image. At the top of the body tube sites the eyepiece.
Coarse Adjustment Knob: The course adjustment knob is found on the side of the microscope. You use this knob to focus your magnified image. This knob focuses the image by moving the body tube/nose piece configuration up and down.
Diaphraghm: The diaphraghm is the device that is used to control how much light is allowed through the aperture, or the hole in the stage.
Eye Piece: The eye piece is the portal to the image and where you look to see the image of what is on your slide.
Fine Adjustment Knob: The fine adjustment knob is also found on the side of the microscope. However, this knob is used to fine tune the focus of the image of your specimen.
Light Source: The light source is found at the base of the microscope. Most student microscopes will have an electric lamp as the light source, however, there are a few more basic models that uses mirrors to capture and focus light from external sources through the aperture.
Nose Piece: The nose piece is found at the bottom of the body tube. You manipulate this piece to select the objective lens magnification that you are interested in.
Objective Lenses: Objective lenses are the tube-like lens heads that are found at the bottom of the body tube. Each lens has a specific magnification power assigned to it, such as 5, 10 or 15 Xs magnification. To select the magnification you want you turn the nose piece which rotates the objective lens you selected to the view position.
Stage: The stage of the microscope is the flat platform that is suspended between the light source and the objective lenses. The stage has a hole in the center of it where the light passes through, this is called the aperture. The stage also has two clips that you will use to secure your slide to the stage.
Tips for Caring for Your Microscope
- Make sure you use both hands when carrying your microscope around. You will use one hand to support the microscope by placing it under the base of the microscope and you will use the other hand to hold the microscope by the arm.
- Avoid jarring or shaking your microscope. This can damage the internal components of the microscope, and damage the alignment of the lenses.
- Make sure you always position your microscope on a solid surface at least three inches from the edge of the surface. This will prevent it from falling off the surface and it will also prevent the microscope from catching on clothing as people in your science class walk by.
- Clean lenses using approved lens wipes. Don’t use paper towels as these can scratch the glass lenses.
- Don’t force the adjuster knobs. If they are sticking check their position and make sure that they are not up against the slide.
Student School Lab HomeSchooling Microscopes
What kind of microscope do you need?
High power or compound microscopes magnify thin specimen sections that are mounted on slides. They are ideal for observing tissues, cells, protozoans, and other microscopic matter not visible to the human eye. Most homeschool families will need this type of microscope.
Low power microscopes are very versatile with typical magnifications of 10 to 40x. These microscopes are designed for viewing whole objects like rocks, insects and flowers, but can also be used for viewing prepared slides.
They are helpful for natural science students and are especially ideal for young children because a slide can be viewed without presenation. Consider a low power microscope as a 2nd choice or as a 2nd microscope because it will not meet your high school biology needs for viewing cell details.
No one microscope can do both jobs of low power and high power.
Now technology has given us even given us more options.
- You can get a DuoScope. Duoscopes allow you to view slide specimens and well as 3D objects such as a flower, rock, leaves. These microscopes have become a favorite for young scientists as well as hobbyists. See image in this section.
- Digital / video eyepieces fit into the lense of your microscope so you can view your specimens on your TV or computer screen!
Tips for Working With a Microscope
- When working with a microscope you have several options for slide creation. If you are having a hard time seeing the details of your sample try other slide creation techniques such as dry slides, wet slides and oil immersion slides.
- If you have long hair keep it pulled back in a ponytail or with clips. This will prevent loose strands of hair from clouding your field of vision and it will also help to prevent your hair from contaminating or disturbing your prepared slide.
More by this Author
Teachers can find information about developing science fair project modules and lesson plans here...
The study of skeletons is the part of most biology classes. If you are working on an anatomy or biology science fair project then you need to learn more about skeletons.
Wind turbines are hot topics right now for science fair projects. Learn a variety of ways to construct these items here...