摘要:

It is shown by elementary arguments that the familiar loudness distribution pattern in the immediate neighborhood of a tuning fork is not, as is often suggested in elementary texts, due to pathlength-dependentphasedifferences between the waves reaching the ear from the different faces of the prongs, but to pathlength-dependentamplitudedifferences. At great distances from the fork, however, amplitude variations become negligible and pathlength-dependent phase differences give rise to a quite different loudness distribution pattern. From an idealized model, which represents a tuning fork as four colinear sources of strengths +B, −B, −B, +B, the velocity potential is calculated and the mean-square-pressure and intensity distributions are derived. It is shown that the mean-square-pressure distribution depends on polar angle(θ)and distance(R)as(3 cos2θ − 1)2/R6close to the fork—the easily audible (amplitude-dependent) nearfield pattern; and ascos4θ/R2at great distances—the less familiar (phase-dependent) farfield case. The intensity distribution comprises acos4θ/R2radial outward flow with, superposed, a circulation of energy from equatorial(θ ≈ 90°)to polar(θ ≈ 0,thinsp;180°)regions, varying with distance as1/R4. There are two zeroes of intensity: whereR = 0.225λ,θ = 0and 180°. The power radiated is estimated for a typical 520 cps fork, and is found to be2.5 × 10−15W when the prongs vibrate with an amplitude of 0.2 mm.

ISSN:0002-9505    

DOI:10.1119/1.1973192

出版商:American Association of Physics Teachers    

年代:1966

数据来源: AIP

摘要:

A simple method is presented for locating sites in diamond-like lattices, and for obtaining the number and locations of their neighbors of arbitrary order.

ISSN:0002-9505    

DOI:10.1119/1.1973193

出版商:American Association of Physics Teachers    

年代:1966

数据来源: AIP

摘要:

The importance of rotational constraints on fluid flow in geophysical and astrophysical problems suggests that demonstrations of these constraints would be useful in undergraduate physics courses. A theoretical derivation of some rotational effects is presented, together with the complete details of four lecture demonstrations which exhibit these effects.

ISSN:0002-9505    

DOI:10.1119/1.1973194

出版商:American Association of Physics Teachers    

年代:1966

数据来源: AIP

摘要:

The shock to which students approaching quantum mechanics for the first time are exposed by the introduction of the postulates on which the mathematical framework of the theory is based, can be much smoothed by a discussion of a semiphilosophical nature about the connection between mathematical theories and the physical reality they are supposed to explain. The general outline of such a discussion is presented, with the purpose of making the introduction of operators to represent physical magnitudes more plausible to the students.

ISSN:0002-9505    

DOI:10.1119/1.1973195

出版商:American Association of Physics Teachers    

年代:1966

数据来源: AIP

摘要:

Various methods of proving that half-integral values of the orbital angular momentum do not occur are discussed and a complete proof is given.

ISSN:0002-9505    

DOI:10.1119/1.1973196

出版商:American Association of Physics Teachers    

年代:1966

数据来源: AIP

摘要:

A number of self-instruction demonstration exhibits with quantitative capabilities have been constructed over the past four years at the Lawrence Hall of Science. Many of them have been exhibited in the laboratories and corridors of local high schools, in the Fleischmann Atmospherium at the University of Nevada, and in a temporary exhibit hall on the University of California campus in Berkeley. A pilot laboratory program is now being conducted with 500 students in the Physics Department. Eleven of the self-instruction exhibit experiments have been set up in a room where students make observations and record data. It is now estimated that this kind of laboratory operation, properly set up, will cost less than twenty per cent of the generally accepted college or high-school laboratory operations, and that forty experiments per year student can readily be performed instead of twenty. These laboratory practices are more effective than lecture demonstrations and are infinitely better than no laboratory at all.

ISSN:0002-9505    

DOI:10.1119/1.1973197

出版商:American Association of Physics Teachers    

年代:1966

数据来源: AIP

摘要:

A modified form of Carathéodory's Axiom II is proposed. Like Axiom I it is phrased in terms of the work in adiabatic processes and, together with Axiom I, it leads directly to the existence of reversible adiabatic surfaces and hence to the concepts of entropy and absolute temperature. The original Axiom II is shown to be a consequence of the proposed axiom. The multiplicity of possibilities that is characteristic of conclusions based on the original Axiom II is eliminated.

ISSN:0002-9505    

DOI:10.1119/1.1973198

出版商:American Association of Physics Teachers    

年代:1966

数据来源: AIP

摘要:

In a recent article, Zatzkis has drawn attention to Hertz's “derivation” of Maxwell's equations from an earlier action-at-a-distance theory. Hertz's procedure leads to an infinite series for the potentials which satisfies Maxwell's equations. It is demonstrated that for a current distribution which is an analytic function of the time this series is the Lagrange expansion of the half-retarded, half-advanced solution of Maxwell's equations; for general source functions the series has no physical meaning. Thus Hertz's procedure does not yield the full Maxwell theory and, in particular, can not account for radiation. It is then shown that, contrary to Zatzkis's contention, in the illustrative example treated by Hertz the original solution is mathematically correct; however, it is physically inadequate.

ISSN:0002-9505    

DOI:10.1119/1.1973199

出版商:American Association of Physics Teachers    

年代:1966

数据来源: AIP

摘要:

A review is given of the procedure by which the electrodynamic gauge group has been used as a guide in the construction of a more complicated gauge group, known as a Yang-Mills group. The field which plays, in this new case, a role analogous to that of the electromagnetic field is discussed. Reference is also made to several recent attempts to relate the quanta of such fields to some of the vector mesons of elementary particle physics.

ISSN:0002-9505    

DOI:10.1119/1.1973200

出版商:American Association of Physics Teachers    

年代:1966

数据来源: AIP

ISSN:0002-9505    

DOI:10.1119/1.1973201

出版商:American Association of Physics Teachers    

年代:1966

数据来源: AIP