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Biology 101: Learning How to Use a Microscope





"The child should never be required to learn the name of anything...but the name should be used so often and so naturally in his presence that he will learn it without being conscious of the process."
-Anna Botsford Comstock, Handbook of Nature Study, p.11.

In order to study microorganisms,  students must first learn how to use a microscope properly. To do this, your student needs to learn the proper vocabulary associated with the microscope. I was most impressed when I was first reading both Charlotte Mason's and Anna Comstock's works how they treated the task of memorizing these types of terms. They suggest that you leave a drawing of the object with the terms labeled on it up in the school area and that, combined with the teacher's proper use of the terms, will lead to the student naturally learning and using the appropriate terms without any special attention paid to the memorization process itself. This was very useful for me because I happen to be that kind of learner myself, having huge difficulty with memorizing lists of things, but not nearly as much trouble memorizing in context.

I have noticed the same is true for many students, even those who find memorizing lists of facts rather easy. When I  taught a group of students biology several years ago, I gave all my students an unannounced end of the year final. I found that a few of the students who excelled on the chapter tests really bombed the final and a few who had only average grades on the chapter tests, received higher marks on the final. After talking to the students,  it seems that the answer was that the students that memorized for the chapter tests used their short term memory, and this information was dumped when the task of memorizing for the next test came along. The students that learned by doing and immersing themselves in the unit only received average grades because they had only been learning about and using the terms for a short two weeks, and hadn't yet completely mastered them yet. By the end of the year, however, they had used, applied and built off of what they had been learning all year and did really well on the cumulative test.

If your student, however, prefers the memorization method, you can practice this with the terms written on Post-it notes and have them put the terms on the correct area of the microscope. Make sure you read through the manual that comes with your microscope to learn the specifics of your instrument.Whatever method you use, make sure you, as the teacher, know and use the correct terms.

To begin your microscope studies, have your student plug in and adjust the brightness of the illumination intensity, and then place the chosen specimen on the mechanical stage and secure it. Make sure that the mechanical stage is farthest position from the objective so that the objective does not touch the specimen slide. Now adjust the x and y stage movement with the knobs so that the specimen is in the center of the viewing area.

Begin with the lowest magnification setting. In our case it was 10x. Next, using the course focus knob, raise the mechanical stage (or lower the objective, if that is how your microscope works) until the objective is close, but not touching the specimen slide. If the student starts with the objective as far from the specimen as he can, the student could accidentally hit the objective against the slide as he goes too close and possibly scratching the lens as well as ruining the specimen or slide while trying to focus the image.

Now your student can focus the image using the coarse focus knob, moving the objective and the mechanical stage farther from each other until the specimen is in focus. Once the specimen is in focus, he can use the fine focus knob to get a sharp image.

Your student can follow the same procedure for the various objectives your microscope may have.

This is the most basic outline of microscope use. Your microscope may have additional features that will need adjustment such as the diopter eyepiece, the iris aperture or the installation of glass filters. You can refer to the manual that came with your microscope to see how to adjust your microscope for these features.

What are some good things to look at initially? 

Starting with a piece of newspaper or a dollar bill can be interesting because it quickly shows the student not only the amount of magnification but also that the images are upside-down and backwards. The student can see that if he moves the paper to the left, the image moves to the right. When he moves the image toward him, the image moves away. Practice with a specimen that is easy to tell this with will make it easier for your student when he gets to specimens for which this fact seems less obvious.

The second specimen I like my students to look at are threads. If you use small pieces of different colored thread, you can show your student how depth of field can affect the image. Have your student put a drop of water on a blank slide sitting on the table. Using tweezers have him place down the first thread. 
Next have him place the second thread on the slide in the same manner, but this time have him place it perpendicular across the first thread so that it makes a cross or X. 
Now have him place the third thread so that it crosses the middle of the X, making a small sunburst type pattern. Now have him place a cover slip over the threads. 
Teach him how to put on a cover slip so as to reduce the possibility of bubbles. To do this carefully place the cover slip so that it is at the edge of the area you want it to go, holding it carefully by its edges. Now, carefully let it fall over the area.
Now have him focus on each thread separately. When one is in focus, the others are out of focus. This will happen when your specimen is not flat.
photo of a "gray" hair, by James using a smart phone camera.
Lastly, I would like to tell you that you can take photographs of the specimens you look at using just a smart phone camera. Just put the camera up to the microscope eyepiece and snap a shot, making sure that the flash has been turned off. As you can see, the photos are not professional quality, but they are nice and can be included in your student's notebook pages. If you print the photos out on regular blank paper, he can make notes or label the parts right on the photo.

2 comments:

  1. I remember getting a microscope for Christmas one year when I was growing up and the awe I felt when I first started looking at things under it. What a magical world! I guess these days kids are used to seeing cool stuff online, but it's still important for them to learn these skills and experience the magic first hand.Thanks for all the ideas. :)

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  2. It's a good point about short term vs. long term memory and its implications. I was definitely "short term" student, but then, in general, I have better memory for trivia than for specific scientific definitions or formulas. I can always look them up :)

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