It has long been known that some optical devices can "magnify" objects. Concave mirror, for example, can magnify objects, which is recorded in Mohist books. As for when the convex lens was invented, it may be impossible to verify it. A convex lens-sometimes called a "magnifying glass"-can focus sunlight and let you see magnified objects, because a convex lens can change the deflection of light. What you see through a convex lens is actually an illusion. Strictly speaking, it is called a virtual image. When the light emitted by an object passes through a convex lens, the light will be deflected in a specific way. When we see those lights, or unconsciously think that they are still traveling along a straight route. Therefore, objects will look bigger than before.
A single convex lens can magnify an object dozens of times, which is far from enough for us to see the details of some objects clearly. /kloc-In the 3rd century, glasses, a kind of lens made of glass, appeared for people with poor eyesight. With the disappearance of the darkness that has enveloped Europe for a thousand years, various new inventions are constantly emerging, and the microscope is one of them. /kloc-At the end of 0/6, Zhan Sen, a Dutch optician, and his son put several lenses into a cylinder, and found that the objects nearby were surprisingly large through the cylinder, which is the predecessor of the present microscope and telescope.
1665, British scientist Robert? 6? When Hooke observed the cork slices with his microscope, he was surprised to find that there was a "unit" structure in them. Hook called them "cells". However, Zhan Sen's compound microscope didn't really show its power, and their magnification was pitifully low. Dutch Anthony? 6? 1 feng? 6? The microscope made by Anthony von Liewenhuke (1632- 1723) opened people's eyes. Levin Hooke learned the technology of grinding glass from an early age and was keen on making microscopes. The microscope he made is actually a convex lens, not a compound microscope. However, due to his exquisite skills, the magnification of the single-chip microscope is nearly 300 times, which is more than any previous microscope.
When Levin Hook aimed his microscope at a drop of rain, he was surprised to find an amazing little world: countless microorganisms swimming in it. He reported this discovery to the Royal Society, which caused a sensation. People sometimes call Levin Hooke "the father of the microscope", which is strictly incorrect. Levin Hooke didn't invent the first compound microscope, but his achievement was to make a high-quality convex lens.
In the next two centuries, the compound microscope has been fully improved. For example, people invented a lens group that can eliminate optical errors such as chromatic aberration (light with different wavelengths will be refracted in slightly different directions when passing through the lens, resulting in a decline in imaging quality). Compared with the microscope of19th century, the ordinary optical microscope we use now has made little progress. The reason is simple: the optical microscope has reached the limit of resolution.
If you just draw on paper, you can naturally "make" a microscope with any magnification. But the fluctuation of light will ruin your perfect invention. Even if the defect of lens shape is eliminated, no optical instrument can image perfectly. It took a long time for people to discover that light diffracts when it passes through a microscope-in short, a point on an object is not a point when it is imaged, but a diffraction spot. If two diffraction points are too close, you can't tell them apart. No matter how high the magnification of the microscope is, it won't help. For a microscope using visible light as light source, its resolution limit is 0.2 micron. Any structure smaller than 0.2 micron is unrecognizable.
One of the ways to improve the resolution of microscope is to minimize the wavelength of light, or to replace light with electron beam. According to De Broglie's theory of matter wave, the moving electron has fluctuation, and the faster the speed, the shorter its "wavelength". If the speed of electrons can be raised high enough and concentrated, it can be used to enlarge objects.
1938, German engineers Max Knoll and Ernst Ruska manufactured the world's first transmission electron microscope (TEM). 1952, British engineer Charles Ottley made the first scanning electron microscope (SEM). Electron microscope is one of the most important inventions in the 20th century. Because the speed of electrons can be increased to a very high level, the resolution of electron microscope can reach nanometer level (10-9m). Many objects invisible to visible light, such as viruses, show their original forms under the electron microscope.
Replacing light with electrons may be an unconventional idea. But there is something even more surprising. 1983, the so-called scanning tunneling microscope (STM) was invented by Gerd Binning and Heinrich Laurel, two scientists from Zurich Laboratory of IBM. This kind of microscope is more radical than the electron microscope and completely loses the concept of the traditional microscope.
Obviously, you can't "see" atoms directly. Because atoms are not the same as macroscopic matter, they are not smooth, and they chop the ball around, let alone within reach? 6? 1 model used by Finch in painting. The working principle of scanning tunneling microscope is the so-called "tunneling effect". If we put aside complicated formulas and terms, this working principle is actually easy to understand. Tunnel scanning microscope has no lens, it uses a probe. A voltage is applied between the probe and the object. If the probe is very close to the surface of the object-on the order of nanometers-the tunneling effect will come into play. Electrons will pass through the gap between the object and the probe, forming a weak current. If the distance between the probe and the object changes, the current will also change accordingly. In this way, the shape of the surface of the object can be known by measuring the current, and the resolution can reach the level of a single atom.
Because of this wonderful invention, Buennig and Basil won the 1986 Nobel Prize in Physics. This year, another person shared the Nobel Prize in physics, that is, ruska, the inventor of the electron microscope.
It is said that hundreds of years ago, Levin Hook kept his technology of making microscopes a secret. Today, the microscope-at least the optical microscope-has become a very common tool for us to understand this small world.