Video Transcript
The micrograph provided is of a group of human liver cells. Which type of microscope is most likely to have been used to produce this image? (A) Light microscope, (B) transmission electron microscope, or (C) scanning electron microscope.
Microscopy is a very important development in biology. Microscopes allow us to view things that are much smaller than the naked eye can see. They magnify things or make them look bigger than they really are.
There are three main kinds of microscopes: light microscopes, transmission electron microscopes, and scanning electron microscopes. Let’s look at how each one works to determine which one was most likely used to produce this image.
Here is a diagram of the path that light follows in a light microscope. A light source illuminates the specimen, the object you want to have a look at, from underneath. The light then travels through the objective lens and the eyepiece lens and into the eye of the viewer. The objective lens and the eyepiece lens both magnify the image of the specimen.
To calculate how much the specimen is magnified in total, we need to know what the magnification of the two lenses are. The total magnification can then be calculated by multiplying the two magnifications of the lenses. For example, if the eyepiece lens magnifies the specimen 10 times and the objective lens magnifies the specimen 20 times, then we calculate 10 times 20 equals 200. And we know that the specimen we see appears 200 times bigger than it actually is.
The observer who is using a light microscope sees a color image. Light microscopes are often used to visualize cells. Light microscopes have a limit of how much they can magnify an object by because of a factor called resolution. Resolution is the minimum distance between two objects at which both are still distinguishable. Since light microscopes use light as an illumination source, their resolution is limited by the wavelength of light. The wavelength of electrons used in electron microscopes is smaller. Thus, they can differentiate adjacent objects that are closer together.
Let’s now take a look at transmission and scanning electron microscopes. Transmission electron microscopes send beams of electrons through their target. This creates a black-and-white 2D image and is often used to differentiate organelles in a cell. Scanning electron microscopes bounce electrons off metal-coated specimens to look at fine details in the outer structure. It creates a 3D black-and-white image.
Now that we understand the principles involved in microscopy, let’s look at the image provided in the question again. It shows a two-dimensional image of the inside of the liver, showing some human liver cells, but doesn’t let us resolve different organelles. It is in color. Therefore, a light microscope was most likely used. So the answer is (A), light microscope.
