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B1 E) Microscopy: Using Microscopes
B1 E) Microscopy: Using Microscopes
There is a diagram of a light microscope below.
The process for using a light microscope is outlined below (the first 4 steps get the slide ready for the light microscope):
- Add a little bit of water to the slide. The little bit of water ensures that the specimen stays in the same position on the slide.
- Cut a thin slice of the specimen and use tweezers to place the slice of the specimen onto the slide. The slice needs to be thin so that light can pass through the specimen (if the slice was thick, little or no light would pass through, thus meaning that we would be unable to see the subcellular structures).
- Add a stain to your specimen. We add a stain to make it easier to see the subcellular structures. There are many different types of stains and the stain that we use depends on what we are trying to see. For example, iodine is good for seeing the subcellular structures in plants, and methylene blue is good for seeing the nucleus and DNA.
- Place a cover slip (which is a thin piece of glass or plastic) on the top of the slide. We place the cover slip by standing the cover slip upright on one side. We then lower the slide until the specimen is covered. We then press down gently to get rid of any trapped air bubbles (air bubbles will obstruct your view of the specimen, so we want to avoid having any air bubbles).
- Place the slide onto the stage and use the clips on the stage to secure the slide in place.
- We then select the lowest power objective lens, which is the lens with the lowest magnification.
- The next step is to use the coarse adjusting knob to move the stage so that the specimen is just below the objective lens.
- We look down the eyepiece and keep moving the coarse adjusting knob until the specimen is in focus or is nearly in focus.
- We then use the fine adjusting knob until the image is in full focus. We then place a clear ruler on the stage to measure the field of view (FOV), which is the diameter of the circular area that is visible when we look through the microscope.
- If you cannot see your specimen, you can change the objective lens to a higher-powered objective lens with a greater magnification. After changing the objective lens, you will need to refocus the image using the coarse adjusting knob and the fine adjusting knob.
Drawing Your Specimen
We draw the outlines of the main features of our specimen with unbroken lines using a sharp pencil. We do not colour or shade any areas on our drawing; this is because our drawing will get confusing and less clear if we were to shade or colour areas. We take as much room as possible when drawing our specimen and we make sure that all of the components are in proportion to each other. We then label any of the key components on our specimen, such as the nucleus, cytoplasm etc. The final step is to title our drawing, write down the magnification (which we get from the microscope) and add a scale.
We draw the outlines of the main features of our specimen with unbroken lines using a sharp pencil. We do not colour or shade any areas on our drawing; this is because our drawing will get confusing and less clear if we were to shade or colour areas. We take as much room as possible when drawing our specimen and we make sure that all of the components are in proportion to each other. We then label any of the key components on our specimen, such as the nucleus, cytoplasm etc. The final step is to title our drawing, write down the magnification (which we get from the microscope) and add a scale.