It is very important to have some knowledge of scientific instruments, otherwise, the topic of the college entrance examination essay may cause a misunderstanding. For example, in 2015, the topic of the college entrance examination essay in Anhui Province caused controversy because of the lack of understanding of electron microscopes (this website also reprinted the news of this incident at that time). The following is the topic of the college entrance examination essay in Anhui Province in 2015.

"In order to enrich the extracurricular life of primary and secondary school students, let them appreciate the charm of science and let them indulge in cutting-edge technology, a research institute of the Chinese Academy of Sciences launched a series of popular science activities on the public open day. During the event, researchers specially designed an interesting experiment to let students operate a scanning electron microscope and observe the wings of butterflies.

Through this microscope that can clearly see the three-dimensional structure of nanoscale objects, the students were surprised to find that the originally colorful butterfly wings had lost their colors and showed a strange uneven structure. It turns out that the butterfly wings are originally colorless, but because of their special microscopic structure, they can show colorful colors under the irradiation of light.

You are required to choose your own angle, determine your theme, specify your style (except poetry), and write your own title; do not write outside the scope of the material and its meaning; do not copy, plagiarize, or disclose personal information; write in a standard manner and use punctuation correctly.

Soon after the college entrance examination, different voices from the "scientific community" appeared on the Internet. Through analysis, "science and engineering men" pointed out that this proposition was "not rigorous enough."

Relevant experts also pointed out that this proposition does have flaws.

The principle of electron microscopy is to use high-energy electron beams to hit the surface of the sample, excite the atoms on the surface (approximately micrometers), and then release backscattered electrons, secondary electrons, Auger electrons, characteristic X-rays, etc. with various atomic signals. The receiver receives these signals and processes them to obtain an image, so it cannot show the color of the object, including butterflies. In other words, whether the butterfly wings themselves have color or not, the electron microscope photo will not show it.

The so-called color electron microscope photos that we can see (such as the one below) are later colored by computer software. They are pseudo-color and are essentially grayscale images, but different grayscale values are defined as different colors.

If a confocal optical microscope is used, since its light source is a xenon light source, i.e. white light, the actual imaging process is to perform a comprehensive imaging of the object's morphology (including color) under the condition of white light illumination, then the color of the butterfly's wings can be seen.