Why does the microscope only output monochromatic images?

You’ve probably all looked at biological slides under a microscope in a high school science lab.

There are a few different types of microscopes, including simple microscopes, dual microscopes, stereo microscopes, electron microscopes, and many more. All of them are used in different situations: some in schools, others in research labs, where scientists examine microscopic things, like the eye of a fly.

If you’ve never seen microscope images, here are a few examples:

Why does the microscope only output monochromatic images?
Did you notice that all of these images have no color?

It is generally believed that the images produced by the microscope are all colorless, that is, they are black and white. And it is, at least to some extent.

So, do all microscopes produce black and white images? If yes, what is the reason behind that?

As mentioned earlier, microscopes come in many different types and sizes, and some of them produce color images. Take the optical microscope as an example.

Why does the microscope only output monochromatic images?
Optical microscope.

The magnified image that an optical microscope produces contains color. In fact, if you use any regular optical microscope with up to 500x magnification , you will be able to see the colors in that magnified image.

However, when you exceed a certain magnification level, colors will start to disappear from the (enlarged) image. That’s because in order to see something under a microscope, the object must have a very thin cross-section. Plus, it also needs to be thin enough for light to pass through it (which is usually the case).

However, if you take a sample that is too small and thin, it won’t have enough material to be able to add color to the light. Think of it this way: when you look at a drop of water, it appears to be completely colorless, but when you look at the ocean – essentially a collection of billions of billions of colorless drops – it looks again a magnificent blue.

Why does the microscope only output monochromatic images?
An ocean is made up of water droplets that are colorless, but are blue (or even green).

Likewise, when you look at a carrot with the naked eye, it’s orange or slightly red, but when you take a small enough slice of the carrot itself and look at it under a microscope, the color Orange almost disappeared.

This is why you don’t see color in an optical microscope, even if you place a colored slide under the lens.

Electron microscopy is completely different. They produce grayscale images of the specimen, i.e., magnified images in black and white. Why so?

When we look at specimens through ordinary optical microscopes, we can see their meticulous details because light reflects off their surface and reaches our eyes. More specifically, it is the photons present in the light that reach our eyes and help us see a magnified image of the specimen.

Why does the microscope only output monochromatic images?
This is the “ray diagram” of an optical microscope.

However, when you have to look at really small things, like the inside of an insect’s eye, an optical microscope won’t help you much. In that case, you need an electron microscope.

Electron microscope, as the name implies, works with the help of fast-moving electrons, unlike optical microscopes (which use photons).

Let’s briefly think that an electron microscope uses a beam of electrons reflected back from a specimen. The “structure” of the reflected electrons is then used to create a 3D image of the magnified version of the specimen.

Why does the microscope only output monochromatic images?
This is an image produced by an electron microscope.

The reason is pretty basic: color is a property of light (photons), and since electron microscopes use a beam of electrons to reflect the specimen, no color information will be recorded. The area where electrons pass through the slide is white, and the area where electrons do not pass is black.

So what you see when you look at the image produced by an electron microscope is essentially a contrast image, that’s why the image is black and white.

You can always add “false” colors to the image produced by the electron microscope, but the colors added to the image are used only to make the image look “more eye-catching” and not related. any relation to the actual color of the specimen in question.

Now scientists have designed a new electron microscope that can produce color images of a specimen. However, the images it produces contain only two colors – red and green. With a few tweaks, the researchers hope to be able to add even more color, allowing them to create vibrant, vibrant images of a fly’s eye!