Let’s try to understand why all color electron microscope images are artificially colorized. If you understand what “380 nm” means, skip this next part on sizes.
Sizes Review
A meter is approximately equal to 3.28 feet.
Formally, a meter is the base unit of length in the International System of Units (SI). It is defined as the length of the path traveled by light in a vacuum during a time interval of 1/299,792,458 seconds. This definition was established in 1983 and is based on the speed of light in a vacuum, which is approximately 299,792,458 meters per second. Look at it this way: in 1 second, light in a vacuum always travels the same distance (186,282.4 miles or 299,792,458 meters). If you divide that known and measured distance into 299,792,458 equal parts, one of those parts is a meter. The small measurements, which include “nm” for nanometers, follow from this.
– Nanometers (nm) are equal to one billionth of a meter. They are commonly used to measure the size of viruses, DNA molecules, and nanoparticles[11][13][15].
– Picometers (pm) are equal to one trillionth of a meter. They are commonly used to measure the size of atoms and molecules[12][15].
– Angstroms (Å) are equal to one ten-billionth of a meter. They are commonly used to measure the size of bond distances between atoms[13][15]. The size of a hydrogen atom is about 0.5 angstroms (Å),
Some conversion factors between these units are:
1 μm = 1000 nm = 106 pm = 10,000 Å
1 nm = 1000 pm = 10 Å.
1 pm = 0.01 Å.
1 Å = 0.1 nm = 100 pm
What Color is: Light Wavelength Differences
What we detect as color is different wavelengths of light. Color is generated when objects are illuminated by electromagnetic radiation in a wavelength area between 380 nm and 780 nm, which is perceivable for the human eye[8]. The visible light spectrum ranges from about 380 to 740 nanometers, and spectral colors such as red, orange, yellow, green, cyan, blue, and violet can be found in this range[6]. Each of these colors corresponds to a different wavelength of light, with violet having the shortest wavelength at around 380 nanometers and red having the longest wavelength at around 700 nanometers[9]. The human eye has evolved to detect light in this range, which we perceive as color[7].
Things Become Invisible at Small Scales
Very small things can not be seen with light microscopes because light itself has a size and some things are too small to change the direction of packets of light. Influencing light is required for us to see objects using light. Light microscopes are limited by the wavelength of visible light, which is around 500nm, so they can only see objects down to a certain size[1][4].
Electron Microscopes
The most powerful electron microscopes allow us to see objects as small as an atom, which is about one ten-millionth of a millimeter or 1 angstrom (10-10 m)[1]. This is why electron microscope are used to see things that are too small for ordinary light microscopes. Images constructed from the bounced electrons look “black and white” because they are not made of light. Color is sometimes added to show one object from another, but electron microscopes do not see in color, because color does not exist at scales that small. That may be a difficult concept to grasp, because our day to day experience of color does not include the details of how light works.
Here is the same virus with a different kind of electron microscope, the kind that requires thin slices but can see in more detail.
To study objects smaller than atoms, scientists must use other tools such as particle accelerators[1].
Citations:
[1] https://www.sciencelearn.org.nz/resources/497-the-microscopic-scale
[2] https://greymattersjournal.org/understanding-the-small-things/
[3] https://www.sciencedirect.com/topics/agricultural-and-biological-sciences/light-microscope
[4] https://www.reddit.com/r/askscience/comments/68nwko/does_anyone_know_what_is_the_smallest_thing_that/
[5] https://www.ruf.rice.edu/~bioslabs/methods/microscopy/microscopy.html
[6] https://en.wikipedia.org/wiki/Color_vision
[7] https://academo.org/demos/wavelength-to-colour-relationship/
[8] https://sensorpartners.com/en/knowledge-base/how-to-perform-a-color-measurement-or-detection/
[9] https://www.amnh.org/explore/ology/brain/seeing-color
[10] https://science.nasa.gov/ems/09_visiblelight/
[11] https://www.varsitytutors.com/hotmath/hotmath_help/topics/metric-system
[12] https://youtube.com/watch?v=-byu5MvrTCo
[13] https://en.wikipedia.org/wiki/Orders_of_magnitude_(length)
[14] https://universalphotonics.com/Portals/0/ReferenceLibrary/conversiontableRL.pdf
[15] http://www.ilpi.com/msds/ref/distanceunits.html
