Lesson Plan - Get It!
Do you believe this big machine is a microscope? It's probably not the kind you are used to!
The image you saw above is an electron microscope that allows scientists to see amazing images under high magnification.
You've probably heard or seen a traditional microscope — called a compound microscope — which is much smaller and can fit on a desk. Compound microscopes use light to create images of materials. Electron microscopes work a little differently — they use a beam of electrons to see very small matter! Electrons are charged particles that make up atoms. They move in a wave-like motion and reflect off particles — much like light waves — creating the image of the specimen or sample.
There are two main kinds of electron microscopes, and you will learn about both during this lesson.
Image by Eric Erbe and Christopher Pooley of the United States Department of Agriculture, via Wikimedia Commons, is in the public domain.
The image above was taken with a scanning electron microscope. Notice how it only shows the surface of the sample. You will explore images from a scanning electron microscope, or SEM, first. Go to Learn to use an SEM, by MyScope Outreach. The simulator walks through how to set up the electron microscope to obtain images. Follow the directions in the simulator, and adjust the brightness to see the final image. You can save or print your creation! Note: The simulation requires Adobe Flash Player.
Now that you know what images a SEM can produce, investigate how they work. Visit How Does an SEM Work?, provided by MyScope Outreach, that explains how an SEM works. As you progress through the pages using the arrow on the bottom right of the page, answer these questions:
- What is the charge of an electron? Why is that important?
- What is an electron gun?
- How are electrons condensed into an electron beam?
- What force pushes the electron beam inward? Why is that important?
- How do the sample and electrons interact?
- What is the purpose of the deflector and detector?
- How are images created?
Scanning electron microscopes can create some pretty cool images using electrons!
Transmission electron microscopes, or TEM, use a very similar process to create images of microscopic samples, but actually pass the electron beam through the sample, instead of on the surface. This allows researchers to study a variety of sample types!
Observe this image of green algae:
Image by Dartmouth Electron Microscope Facility, Dartmouth College, via Wikimedia Commons, is in the public domain.
- How does it compare to the previous image taken with a scanning electron microscope?
In TEM images, we can see through the sample because the electrons pass through the sample!
- What have you learned about the difference between scanning electron microscopes and transmission electron microscopes?
- Can you think of specific samples that would require one or the other?
Using electrons instead of light really increases the detail and magnification of specimens compared to light compound microscopes.
Discuss your answers to these questions with a parent or teacher.
Continue to explore the uses of SEM and TEM in the Got It? section of this lesson.