Cambridge International AS And A Level Physics Coursebook With CD-ROM (Cambridge International Exami
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In Section 6.2.2 the history of atomic spectroscopy is considered. This section also presents the exciting story of experiments leading to the Bohr model of the atom (12.6.2). After considering the fine structure of hydrogen, this section returns to the Bohr atom to consider the transition between discrete energy levels. The theory of spectroscopy is briefly outlined (14.3.2).
This section considers energy both in terms of the units used to measure it and in terms of the basic units of energy in physics. It is at this point that the mass energy equivalence (E=mc2) is shown to be a fundamental principle of physics, and it is shown that the rest energy of an electron is a conserved quantity (section 6.3.1). The conservation of energy is an important idea in learning physics, and it is used to give a crude model for a particle as a particle travelling through space at a constant velocity. The spread of a wavepacket (the uncertainty principle) is discussed. It is seen that energy conservation leads to a value of the speed of light that is different from the value obtained from Doppler shift measurements. The rest energy of a neutron is considered in terms of the quark model and finally the rest energy of a proton is considered in terms of the quark model.
The second section (6.2.2) considers a range of experiments that measure the magnetic moment of particles. It is here that the fundamental properties of the electron are considered, including spin and the relation between spin and polarization of the photon. The origin of the electron’s magnetic moment is considered in the context of the electron as a bound state of a positron and an electron. This section also includes an introduction to a general discussion of experimental methods and the problems in accounting for those errors that arise when measuring things. Here again, the opportunity to consider learning and the development of physics models is available.
The third section (6.2.3) covers the discovery of the weak force. Electromagnetic interactions become the dominant interaction between charged particles, and we are left with only weak interactions as a possible source of the new force. This is the birth of the standard model of particle physics and the search for the Higgs boson (HW11). 827ec27edc