Introduction to Microscopes - Online Tutor, Practice Problems & Exam Prep

Microscopes are essential tools for visualizing microbes, which are too small for the naked eye. There are two main types: light microscopes, using visible light for magnification, and electron microscopes, which utilize electrons for higher magnification. Light microscopes can visualize most bacteria and eukaryotic cells, while electron microscopes are necessary for observing viruses and smaller macromolecules. Understanding the size ranges of these objects, from atoms to human cells, is crucial for studying microbiology and cellular biology.

Introduction to Microscopes

In this video, we're going to begin our introduction to microscopes. As you already know, microbes are simply way too small for our bare eyes to see on their own. Our eyes require the aid of microscopes in order to visualize those incredibly small microbes. A microscope, as its name implies, is an optical scope or instrument that is used to visualize microscopically small objects, such as cells, for example. Recall that the root 'micro' means small. Now, moving forward in our course, we're going to talk about two main types or groups of microscopes that are commonly used.

The first main type is the light microscopes, which, as its name implies, use visible light to magnify small objects and make those small objects appear larger. The second type of microscope that we will discuss moving forward is the electron microscopes, which, as their name implies, use electrons for an even higher magnification of even smaller objects. The electron microscope is a much more powerful tool and is therefore a lot more complex and expensive than the light microscopes.

As we move forward, we'll be talking about different types of light microscopes and different types of electron microscopes. But for now, let's take a look at this image below, which shows you the ranges of the human eye, light microscopes, and electron microscopes as well. Notice in this image, it shows a bunch of objects across the top arranged in terms of their size. The further to the left are the really, really small objects, and as you go to the right, the larger objects. This image helps to put things in perspective a bit.

Notice on the far right, the largest object that we're showing is actually a human. On the left, the smallest object we are showing here are atoms. Below, we have this scale showing you the ranges in terms of their sizes. It goes from 10 meters to 1 meter, to 1 centimeter, to 1 millimeter, and so on. The smallest unit we have down here is called angstroms. One angstrom is an extremely small unit.

This green region represents the human eye. Our eyes are able to see really large things, but there's a limit to how small we can see with our bare eyes. We are able to see objects such as ants, and some cells, like frog eggs which are quite large, but most plant and animal cells and most bacteria and archaea are simply way too small and outside of the range of our eyes to see. In order to visualize cells and smaller objects, scientists need to use microscopes.

There are two main types of microscopes that we'll talk about, moving forward. The range of the light microscopes is right here, in this blue range. Light microscopes can be used to visualize most bacteria and archaea, and most animal cells, but they are not generally powerful enough to visualize viruses. To visualize viruses, which are smaller than most bacteria, archaea, and eukaryotic cells, we need a more powerful type of microscope, called the electron microscope. The range of the electron microscope allows for the visualization of much smaller objects, including most viruses and even smaller molecules like water molecules and macromolecules like proteins and lipids, and some atoms as well.

This image is just a cool way to put things into perspective and show how these different objects compare to each other in terms of their size. A few things to note here that will be important as you move forward in the course. Most plant and animal cells, which are eukaryotic cells containing a nucleus, are going to be larger than most bacteria and archaea which are prokaryotic. Prokaryotic cells tend to be smaller than eukaryotic cells, and that's something that we'll touch on more as we move forward. Another thing to note is that viruses are much smaller than even bacterial cells, and usually, viruses can only be visualized with electron microscopes, an idea that we'll also emphasize more as we move forward. But for now, this here concludes our brief introduction to microscopes.

Once again, we'll be able to learn a lot more about these different types of microscopes moving forward. So I'll see you all in our next video.

The basic unit of life is a cell. What type of microscope can be used to visualize prokaryotic cells?

• A. Light microscope.
• B. Electron microscope.
• C. Both light and electron microscopes.
• D. None of the above, cells can be seen with the human eye.

Which type of microscope would be the BEST selection for the examination of muscle proteins?

• A. Light microscope.
• B. Electron microscope.
• C. No microscope would be needed to visualize muscle proteins.

Here’s what students ask on this topic:

What are the main differences between light microscopes and electron microscopes?

Light microscopes use visible light to magnify objects, making them suitable for viewing most bacteria and eukaryotic cells. They are relatively simple and less expensive. Electron microscopes, on the other hand, use electrons for higher magnification, allowing visualization of much smaller objects like viruses and macromolecules. They are more complex and costly. Light microscopes typically achieve magnifications up to 1000x, while electron microscopes can reach magnifications of up to 2 million times. Additionally, electron microscopes require a vacuum environment and special sample preparation.

Why are electron microscopes necessary for observing viruses?

Viruses are much smaller than most bacteria and eukaryotic cells, often measuring between 20 to 300 nanometers. Light microscopes, which use visible light, do not have the resolution to visualize such small particles. Electron microscopes, however, use electrons with much shorter wavelengths than visible light, providing the higher resolution needed to see viruses. This allows scientists to study the detailed structure and morphology of viruses, which is crucial for understanding their function and developing treatments.

What types of objects can be visualized with a light microscope?

Light microscopes can visualize a range of objects, including most bacteria, archaea, and eukaryotic cells such as plant and animal cells. They are also capable of viewing larger microorganisms like protozoa and some fungi. However, light microscopes are generally not powerful enough to see smaller objects like viruses, macromolecules (proteins, lipids), or individual atoms. For these smaller objects, electron microscopes are required.

How do the size ranges of objects affect the choice of microscope?

The size of the object being studied determines the type of microscope needed. Objects visible to the naked eye, such as ants or frog eggs, do not require a microscope. For most bacteria, archaea, and eukaryotic cells, a light microscope is sufficient. However, for smaller objects like viruses, macromolecules, and atoms, an electron microscope is necessary due to its higher magnification and resolution capabilities. Understanding these size ranges helps scientists choose the appropriate tool for their research.

What are the limitations of light microscopes?

Light microscopes have several limitations. They are generally limited to a maximum magnification of around 1000x, which is insufficient for visualizing very small objects like viruses and macromolecules. Their resolution is also limited by the wavelength of visible light, making it difficult to see fine details within cells. Additionally, light microscopes cannot visualize objects that are smaller than approximately 200 nanometers. For higher magnification and resolution, electron microscopes are required.