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2. The arc appears under the condition that the voltage between the cathode and anode exceeds 50 V. We designed our experiment for the voltage 60 V, but in reality we obtained even higher value: 65 V (see the picture at right). 3. Performance of the
arc did not depend on the polarity of the electrodes. With the negative voltage
on the graphite electrode, the last served as the cathode, accelerating
electrons, while the bolt served as the anode, i.e., it attracted and absorbed
electrons. With the opposite polarity, the electrodes changed their functions.
4. The speed of electrons,
accelerated in the arc, can be determined from the equation:
where
Physics
Propagation of light through crystals
1. The goal of this experiment was to study depolarizing effect of sugar and salt crystals.
2. It is known that some optical materials act as polarizers - optical elements transmitting light waves of only one orientation. The two crossed polarizers do not transmit light at all. Look at the figure at left: the polarizer and the analyzer (same material positioned after the polarizer in order to analyze the picture) are crossed. It means that we shall see black picture in the microscope. If, however, the crystals are optically active, i.e., if they influence orientation of the optical wave, then bright dots will be visible in the microscope at those points where orientation of optical wave was changed by a crystal.
3. This is how the crystals look like under ordinary (non-polarized) illumination. Not very straight yellow line separates the crystals of salt and sugar. 4. The lower picture shows same pile of crystals observed in crossed polarizers. Obviously, the crystals of salt are less optically active: they do not change polarization of light and, therefore, are dark. As to the sugar, it is more optically active: its crystals look bright. White lines drawn from one side of the analyzer to another indicate direction of the polarization axis.
Chemistry
Electrolysis of potassium chloride solution 1. The aim of this experiment is to observe the microscopic processes of electrolysis.
2. First, we have cut a small piece of about 5´1 sm2 out of a flat cable from an old printer, removed the isolation from the upper side with a soldering gun, and soldered two wires to two neighboring leads of the cable. As a result, we got two electrodes 0.5 mm wide each separated by a 0.2 mm gap. It is experimentally known, that in such a micro-experiment, a 1.5 V battery is enough. Then we applied a droplet of potassium chloride solution on the bare sides of the electrodes and watched the result in QX-5 microscope. 3. Double-click on the picture below to watch the movie of the electrolysis process.
Electrolysis video. 4. The electrolysis of the solution follows the following scheme: 5. 2NaCl+2H2O®H2+Cl2+2NaOH After evaporation of water due to heat, only the dry foam of NaOH is left. Biology
The blood clotting process 1. The aim of this experiment is to observe the process of blood clotting on the open air. 2. It will hurt: we need a drop of fresh blood for the experiment. We used a pipette to put the blood on the glass slide and then watched it in the QX-5 microscope. 3. Double-click on the picture below to watch the blood clotting process.
Blood clotting video. Biology
Bean growing 1. The aim of this experiment is to observe the first stages of the bean seed’s growth. 2. We have bought the seeds in Suwon Home-Plus supermarket. We placed a damp cloth at the bottom of the Petri dish and put the seeds on it. Then we adjusted the QX-5 microscope for continuous recording and positioned it on the floor in order to prevent any vibrations. As a final precaution, we turned on the heating. The time interval between shots was set to 15 minutes, and we waited for 3 days. 3. Double-click on the image below to watch the growth of the bean embryos.
Bean growth video. 4. At first, the beans were cold and grew slowly. Then, we have increased the temperature, and their growth accelerated. The appearing roots reached for the water. You can see small secondary roots, growing on them like hair. For three days, the water was being added to the dish, and the beans quickly consumed it. Then, we stopped adding water, and the beans died. Biology
Functioning of moss as of an entire organism 1. The initial aim of the experiment was simple - to observe moss. But in the end, we have discovered something more interesting: moss, in fact, lives as one entire organism. 2. We put the moss sample into a Petri dish, soaked it with water and exposed to the sun. It survived, and remained green and fresh for several days. Then we took a small piece of moss from the colony and put it under the microscope, not without water of course. And then, totally unexpectedly, it started to wither, and was dead in 5 minutes. 3. Double-click on the picture below to watch this process.
Moss video. 4. It seems that moss lives as a colony. Isolated small pieces of this colony are unable to sustain themselves even in perfect living conditions: in presence of both water and appropriate temperature. Those unusual ordinary things
In this section, you can take a look at usual things under big magnification. And then, we shall discover many interesting details.
Left: tip of an ordinary needle and the tip of a chestnut. Right: service track of a compact-disk.
500 Euro banknote. Left - in transmission mode, right - in reflection mode. Both at left and at right the same area of the banknote is shown.
Human hair cut. It is solid, although we can hear sometimes that people say it has an axial channel inside. Don’t believe it!
And this is a
well-known Velcro fastening material. At left - at magnification 60´, at right - at magnification 200´.  
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