Micro-photography: Not only a change of way of seeing (3)

    Let's take a look at the big-guns we are using in Micro-photography: microscopes.

    This is an optic microscope, the most commonly-used observing tool in Biology. It is not a high-techie tech that emerged in recent years. Its history traces back to more than 300 years ago, when Robert Hooke, an English scientist built the first optic microscope from the inspiration of Galileo's telescopes. Yes, it does works similarly with refracting telescopes: they all use a set of convex lenses to magnify the objects. But microscopes deal with very small objects at a very close distance, while telescopes are used to watch distant stars and galaxies. Though the theory is very simple-even a high school student today knows how it works-it is not so easy to make one. As the power increases, the lens needs to be polished very precisely, and the composition of glass used for making lenses becomes very important because even a tiniest bit of impurity would disable the microscope from working. Therefore, only a few manufacturers in the world can build high-power optic microscopes, with up to 2500x magnification power. 

    Though the magnification power is enough to observe most of the microscopic cells and crystals, optic microscopes are rarely used in micro-photography because they work poorly with cameras. Cameras also use sets of lenses to form images, so optical distortions may occur if these lenses are combined with the lenses in the microscopes. There are, in fact, some microscopes that work in coordinate with cameras, but they are hard to build, even more complicated than the other type of microscope I'm introducing next, the Electron Microscope. 

    The invention of electron microscopes is definitely one of the biggest victory of Quantum Physics (another one is CD-Player). In wave-particle dualism theory, any substance in the world have both characters of wave and particle. But we never consider ourselves a bunch of waves because our wavelength is too small to measure, only sub-atomic particles travelling at high speeds can express an observable dualism, one example is electron.

    But why electron instead of light? This is because the wavelength of visible light is 390-780 nm. Higher magnification power means shorter focus length. As the power goes to beyond 1600x, the focus length is so close to the wavelength of visible light that the light no longer focus in the manner it has to be. Thus, we can barely get a clear image when the power is too high. One solution is using UV rays, and this can extend the ability of optic microscopes to 2500x. But still, 2500x is not enough to let us see viruses or molecules. 

    Therefore, we use electrons, which has a wavelength of only 0.1 nm. Though electrons don't focus when going through a lens, they can focus in magnetic fields. Now imagine a combination of an electron accelerator and a magnetic lens-how similar it is to an optic microscope! It is true that electron microscopes work just in the same way of an optic one. The only difference is the "light" we are using, namely high speed electrons and visible light. 

    Electron microscopes work in coordinate with electron sensors, so when electrons hit the sensor, a dot will appear on the screen. Thus we can directly have an image without observing it with our own eyes (caution: human cannot detect electron rays, but they are harmful to eyes). What's more, by adjusting the speed of electron and the intensity of magnetic field, we can get any magnification power we want. In comparison, optic microscopes can only provide a certain sets of power and the photographer may be caught in the dilemma of having either too big or too small pictures. 

    All these advantages make electron microscopes the favorite of many micro-photographers. Over 90% of the micro-photos are taken by electron microscopes.

    Compared to this gigantic monster, however, even electron microscopes are but an entertainmant-level equipment. This is the STM (scanning tunnel microscopes), the most delicate machine on the planet-it requires even higher precision than building a spaceship. It is the only thing that can bring us to atomic level-namely less than 0.1nm. Their working principle is very complicated so I'm not going to introduce it here. The only thing you need to know is: it has a magnification power of over a million times! 

    The picture above shows only the smallest STM, take a look at this guy! It is the biggest microscope ever built, finished in 2007 in Oxford University, UK. Its size is equivalent to 5 soccer fields, or 150 meters in diameter. It can produce the highest light intensity in the whole universe: 1 million times brighter than all the light source ever detected in the universe! What a monster!