Giáo trình Tiếng Anh nâng cao chuyên ngành Vật lý: Phần 2 cung cấp cho người học những kiến thức về vật lý thống kê (Statistical physics). Phần này cũng hướng dẫn các bạn thực hành viết báo cáo khoa học và trình bày trước lớp. Mời các bạn cùng tham khảo. | Tron Bo SGK https CHAPTER 4 STATISTICAL PHYSICS PART Reading English-Vietnamese translation See 39. The Equilibrium Distribution o f M olecules in an ideal gas The subject o f statistical physics T he methods of quantum mechanics set out in the third chapter make it possible in principle to describe any assembly o f electrons atoms and molecules comprising a macroscopic body. In practice however even the problem o f an atom with two electrons presents such great mathematical difficulties that nobody so far has solved it completely. It is all the more impossible not only to solve but even to write down the wave equation for a macroscopic body consisting for example o f 102 atoms with their electrons. k J Download Ebook Tai https Tron Bo SGK https 168 CHAPTER 4. STATISTICAL PHYSICS Yet in large systems we encounter certain general laws of motion for which it is not necessary to know the wave function of the system to describe them. Let us give one very simple example of such a law. W e shall suppose that there is only one molecule contained in a large completely empty vessel. If the motion of this molecule is not defined beforehand the probability o f finding it in any half of the vessel is equal to 1 2. If there are two molecules in the same vessel the probability of finding them in the same half of the vessel simultaneously is equal to l 2 2 l 4 . The probability o f finding all of a gas consisting of N particles in the same half of the vessel if the vessel is filled with gas is l 2 N . an unimaginably small number. O n the average there will always be an approximately equal number of molecules in each half of the vessel. The greater the number o f molecules forming the gas the closer to unity will be the ratio of the num ber of molecules in both halves o f the vessel no matter at what time they are observed. This approximate equality for the number of molecules in equal volumes of the same vessel .
