- •І. С. Холмогорцева а. В. Котова english for physicists
- •Навчальний посібник
- •Передмова
- •Part I. General course Unit 1
- •Passive voice
- •Study the following words and word combinations
- •Particles and Fields
- •Where Does the Thunder Come From?
- •Modal verbs
- •Modal verbs with perfect infinitive
- •Study the following words
- •Physics Lab Safety Rules
- •Our Place in the Universe
- •Conditionals
- •Subjunctive mood
- •Study the following words
- •Properties of Light
- •The Atomic Structure of Matter
- •Participle I
- •Study the following words
- •Cutting Through a Myth about Modern Lasers
- •Participle II
- •Absolute participle construction
- •Study the following words
- •Fun Facts about Lasers
- •Study the following words
- •The World Is Made of Subatomic Particles
- •The Big Bang Theory
- •Infinitive
- •Bare infinitive
- •Fiber-Optic Technology
- •Gerund vs. Infinitive
- •Copper and Technology
- •Test yourself Quantum world record smashed
- •V. Grammar test. Choose the correct form.
- •Part II. Special skills Resume
- •Creating The Effective Resume
- •Fill in the Blank Resume Form _______________________
- •Business Letters Layout
- •Inside Address
- •Business Correspondence
- •Study the following word combinations Phrases that can be used in all kinds of business letters
- •Summary and Abstaract Writing
- •Tips on writing an abstract
- •Part III. Additional reading Plasma
- •Plasmas in space
- •Mechanisms of Electron Losses: Electron-Ion Recombination
- •The mhd equations
- •Elements of Quantum Mechanics. History
- •Density dependence of the quark structure of light nuclei
- •An astrophysical application: alpha-capture reactions
- •Dating the Shroud of Turin
- •Double Beta-Decay
- •Advances in Carbon Nanotube Characterization
- •How lasers work
- •Appendix 1 List of irregular verbs
- •Appendix 2 Guidance on reading terminology
- •1. The plural of the nouns of Greek and Latin origin
- •2. Numerals in English
- •3. Signs and symbols
- •4. Latin terms and abbriviations
- •5. Greek alphabet
- •Appendix 3 Useful phrases for abstracts
- •Reporting Verbs
- •List of References
- •Contents Передмова…………………………………………………………………………3
- •Англійська мова для студентів фізичних спеціальностей
- •61022, М. Харків, майдан Свободи, 4.
Elements of Quantum Mechanics. History
Max Planck laid the foundations of quantum physics in 1900 when he assumed that light of frequency v was emitted and absorbed in packets called photons or quanta, with energy given by
E = hv (1)
Planck made this bold hypothesis to explain the observed spectral- emitting power of black body cavities at various temperatures. Planck's constant h can be evaluated by confronting his theory with the experimental data. This constant is basic to quantum physics; in fact, letting it approach zero is a formal device for testing quantum equations to see whether they reduce, as they should, to classical equations under conditions for which quantum effects are not important.
From 1900 to the early 1920's, the structure of what is now called "the old quantum theory" developed. A high spot was Bohr's theory of the hydrogen atom (B13). Implicit in this is the important notion that an atomic system can exist in a discrete set of stationary states of total energy El, E2 , … , En , and that light is emitted or absorbed when the system changes from one of these states to another. The frequency of the light is found from Bohr's frequency condition
ωnm = (En—Em)/h (3)
which combines Eq. 2 and the conservation of energy principle. In spite of the impressive successes of the old quantum theory, there were some points of disagreement with experiment. Also, there were a number of measurable quantities for which the theory did not seem able to make predictions. It was slowly realized that this theory had not made a clean enough break with classical physics.
In 1926 Schrodinger (S26) developed an improved quantum theory called wave mechanics; it is based on the notion that matter can be described in terms of waves. In the same year Born, Heisenberg, and Jordan (B26), following up an idea formulated by Heisenberg the previous year (H25) developed another form of quantum theory called matrix mechanics; this is based on a feeling that the "raw facts" of atomic physics, e.g., the spectral frequencies, should be built solidly into the theory in a central fashion and that doing so is more important than hanging the theory on a particular model. This theory is particle-oriented, in contrast to the wave orientation of Schrbdinger’s theory. Although the two theories seem quite different, they lead to identical results.
In 1948 Feynman, then of Cornell University, invented still a third form of quantum mechanics (F48). The operationally inclined reader will not spend much time wondering which of these equivalent theories is "true." All three theories represent a fresh start rather than an attempt to patch up classical physics. This seems wise since classical theory is a special case of quantum theory, rather than the converse.
Neither wave nor matrix mechanics took into account the special theory of relativity. Dirac remedied this defect in 1928 with his relatiuistic quantum mechanics (D28). With its aid he was able to predict the existence of the positron before it was discovered in the cosmic rays by Anderson (A33). Dirac's theory also predicts the spin of the electron in a natural way. Uhlenbeck and Goudsmit (U25) deduced empirically from studies of atomic spectra that the electron must have a spin of Yz. This does not appear without some "forcing" in the non-relativistic quantum theories, however. Although relativistic quantum mechanics (or quantum electro- dynamics) involved some rather arbitrary and disturbing mathematical procedures, it did seem, up to 1947, to be in complete accord with experi- ment when applied to systems, such as atoms, involving electrons and radiation. In that year however, Lamb and Retherford of Columbia University (La47) discovered a small but definite discrepancy between theory and experiment in their careful study of the fine structure of the hydrogen spectrum. This spurred on a reinvestigation of the foundations of quantum electrodynamics. In the hands of Kramers, Schwinger, Bethe, Dyson, Tomonaga, and others, it became possible to reformulate the theory so as to account quantitatively for the results of the Lamb-Retherford experiment. Though cumbersome in its present form, modern quantum electrodynamics now seems to give precise answers when applied to atomic problems. It contains what Dyson (D52) calls a built-in miracle, in that certain expressions, whose presence in the final result would be embarrassing, always conveniently cancel, even though it is not clear why they do. Theoreticians are trying now to reformulate quantum electrodynamics with the hope of gaining new insights.