Back To CourseFundamental Biology
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Sarah has two Master's, one in Zoology and one in GIS, a Bachelor's in Biology, and has taught college level Physical Science and Biology.
As we get older, our eyes are not able to see things as clearly, especially things that are small. We may get a magnifying glass in order to help us read and see small objects, and this helps because magnification makes the object appear bigger so we see it more clearly.
A microscope does the same thing, but for very, very small objects. The most common type of microscope you'll use in your biology labs is a compound light microscope. This microscope has two lenses that bend light so that a specimen is magnified and projected. Having two lenses is very important because this is where the microscope gets its name. To compound something means to add to it - like compound interest, or a chemical compound, which is a sum of multiple parts. The word microscope is also key, because micro means small and scope means view.
You may have noticed the word 'light' in the name of this microscope, and that's also no accident. This type of microscope uses visible light, which is the part of the light spectrum our eyes can see, and passes it through the lenses. The lenses bend the light so that the object you're looking at appears larger than it is. This allows you to see it better.
The resolution, or clarity of an image, is also an important factor when looking through a microscope. A standard compound microscope can magnify objects about 1,000 times, which is pretty good! But above this the image becomes blurry, so even if an image appears larger it may still not be very clear unless the resolution is good.
Compound light microscopes have been around for quite some time now. They were first used in the 17th century. It's no coincidence that during this same time cells were discovered, which led scientists to a great number of other discoveries about microorganisms and cell structure and function.
Microscopes are very powerful tools indeed, but in order to use one properly, you need a basic understanding of its components. Quite possibly the most important part of the compound light microscope is, well, the light source! Ok, maybe the power switch is the most important part because that is what allows you to have light in the first place. But the light source is definitely next on the list of important parts! It is found at the base of the microscope and you can adjust the brightness of the light by rotating the light source knob.
Moving up from the light source we find the stage. This is directly over the light source and is a flat area that holds your slide or specimen flat. On the stage, we find the aperture, which is a small hole in the stage that allows light to pass through. Whatever part of your slide or specimen is directly over the aperture is what you'll see when you look through the microscope.
Also on the stage are the stage clips. These are used to hold your slide in place, and they simply clip over the edges of your slide to hold it down. There will be a knob near the stage called the stage control that moves the stage clips so that you can look at different parts of your slide without having to move it by hand.
As we continue to move up from the base of the microscope we find the objective lenses, which are attached to the nosepiece. The objectives are how much the image is magnified, and the number is written on the side of each objective with a number and the letter X. For example, if you see 10X on the side of an objective, this means that the object is magnified 10 times. Most compound microscopes have 3 or 4 objectives, and they will most likely be 4X, 10X, 40X, and 100X. The nosepiece adjusts so that you can turn from one objective to the other, depending on how much magnification you need for your specimen.
Above the objective lenses is the body tube, which is connected to the eyepiece. The eyepiece is what you actually look through to see your specimen, and the body tube connects this to the objective lenses. The eyepiece is yet another point of magnification, so while your objectives have a magnification of 4, 10, 40, or 100 times, the total magnification of the microscope is this multiplied by the magnification of the eyepiece. Usually, the eyepiece magnifies objects 10 times their size, so if you combine this with the objective lens magnifications, you would have a total microscope magnification of 40X, 100X, 400X, and 1000X.
In order to get the best image possible, there are two knobs that you should be aware of. One is the coarse adjustment knob and the other is the fine adjustment knob. The coarse adjustment knob does just what is says - it allows for broad, coarse adjustment of the image. Once you get the image in about the range of focus that you need, you can use the fine adjustment knob to get it just right.
The microscope also has an arm which is the part that supports the body tube and connects it to the base. The base is simply the part of the microscope that rests on the table and supports the microscope itself. The arm and base are important because if you ever need to carry or move a microscope, these are the parts you use to do so. To safely move a microscope, simply grasp the arm with one hand while placing the other hand under the base. This will prevent you from dropping or breaking the microscope, which your lab instructor will greatly appreciate!
No matter how large or small, a microscope is a delicate piece of equipment. It's important to use great care when using, cleaning, or moving the microscope. This will ensure that you, your lab mates, and future biology students are able to use and enjoy the microscopes for as many lab activities and experiments as possible.
Named for its pair of lenses and use of a light source, the compound light microscope was first used in the 17th century. The invention of this type of magnifier led to great discoveries of cells, cell structure, and microorganisms.
This type of microscope magnifies images through two lenses to make the specimen or image on the slide appear larger than it is. There are several different magnification settings that a microscope may have, but the total magnification of the image is always the magnification of both the eyepiece and the objective lens being used.
Microscopes are very useful and powerful laboratory tools. They provide us with a fun and easy way to see things that would otherwise be un-seeable. Because of this, great care needs to be taken when using a microscope. Proper knowledge of how to use, clean, and move a microscope ensures that it will be around for many uses and lab activities.
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Back To CourseFundamental Biology
36 chapters | 333 lessons