Compound Microscopes
A User’s Guide to Compound Microscopes
At least three great scientists from the past have been largely credited as the inventors of the compound microscope. In any case, compound microscopes are now used in various fields within and outside science.
How Compound Microscopes Work
Both simple and compound microscopes have light sources. These could be either mirrors or lamps, and they may be self-illuminating or not. When a light source gives off light, this passes through the object – which is why samples or specimens used must be thin enough for light to pass through easily – and allows the microscope’s objective lens or lenses, as it is in the case of compound microscopes, to produce a bigger image of the object.
Now, you’ll be looking at the sample through the microscope’s eyepiece. The eyepieces are able to make the already enlarged image of the object even bigger. If you are using a 4x objective lens together with a 10x eyepiece, you’ll end up seeing the object forty times bigger than it actually is.
There is of course a limit to how much magnification is allowed and it has more to do with your capabilities rather than those of a microscope. Most compound microscopes limit their magnification to 2000x. Anything beyond that and your brains and eyes wouldn’t be able to decipher the image. If you want to see something smaller, you’ll have to work with an electron microscope. An electron microscope uses an electron source instead of a light lamp to make you see viruses and atoms, but that’s another story.
How to Use Compound Microscopes
The main advantage and difference of compound microscopes from simple microscopes are the provision and use of two lenses. Simple microscopes only have one. With two, you’ll be able to see better and more. Besides that, the same steps for using can be applied.
Look for the best place to place your compound microscope. Avoid places that could subject your microscope to vibration as this could affect the position of your slides. Switch on your light source then adjust the light level using your microscope’s diaphragm.
Choose the best objective for your sample. Rotating the nosepiece and trying out each objective one by one will help you find the ideal measurement. When you’ve made your choice, you should be hearing a clicking sound to signal that your objective and eyepiece are aligned.
Put your slide in position. Lock them in with the stage clips. Use your coarse knob to start adjusting the eyepiece away instead of towards your specimen. Never ever do anything to risk damaging your microscope’s lenses because they’re extremely costly to replace or repair. Adjust the fine knob then adjust the diaphragm again. If they’re all set, you’re now ready to view your specimen in comfort.
How to Make a Wet Mount for Slides Used for Compound Microscopes
If you need to make a wet mount, start by placing one drop of water on your slide. Put the object on your slide before slowly lowering the glass cover. Make sure to avoid making air pockets as these could damage the purity of your specimen. Once you’ve placed the glass cover securely, use lens paper to absorb excess water from the slide.
How to Stain Slides Used for Compound Microscopes
If you are not using brand new or recently cleaned lenses, use a Bunsen burner to flame one side of your slide and remove oil residues or grease stains. Wait for the slide to cool before putting a drop of water on the center of the slide. Use an inoculating loop to do so. Place the specimen on the wet spot in your slide. Mix if necessary.
Use your inoculating loop to spread the specimen thinly on the slide. Wait for it to dry before heating it. Heat will ensure that your specimen will be kept in place. Put your heated slide on a staining rack then cover it with crystal violet stain or anything similar. Leave it for one minute. Afterwards, allow the stain to run off then rinse with water. Blot gently to let the slide dry out gradually.
Once the slide has dried out completely, you can now examine it under the oil immersion lens of your compound microscope. Make sure to use immersion oil.
If you are going to take compound light microscopes with you to field work, make sure to carry it with one hand supporting its base while the other holds the equipment by its nosepiece. If not in use, return the microscope to its original packaging as much as possible. Do not touch the lenses at all cost as even the smallest speck of dust can affect your visuals.
