摘要:

Reflections and refractions of a sheet of light from a truncated cone are shown to produce the ancient figure of the conchoid of Nicomedes when imaged on the basal plane. The idea can be easily demonstrated using a truncated cone (here a glazed flower pot is used) and a laser pointer. This result may be of interest in the area of nonimaging optics.

ISSN:0002-9505    

DOI:10.1119/1.18193

出版商:American Association of Physics Teachers    

年代:1996

数据来源: AIP

摘要:

The success of calculating and displaying the Fraunhofer diffraction patterns for various apertures using the fast Fourier transform algorithm on an IBM compatible personal computer has been well documented in the recent literature. In this paper the technique is extended to the simulation of optical holography on the computer. Using this method, Fourier transform holograms are easily generated. Their optically reconstructed images are compared to the ones reconstructed and displayed by the computer. These computer generated images allow for a quantitative verification of the holographic theory presented and can serve as the basis of a tutorial on this subject suitable for advanced undergraduates. The calculations and graphics were accomplished using themathcad(R)forwindowsTMsoftware package.

ISSN:0002-9505    

DOI:10.1119/1.18194

出版商:American Association of Physics Teachers    

年代:1996

数据来源: AIP

摘要:

A classroom demonstration is described which illustrates how a cryogenic fluid, liquid nitrogen, can be used to run an open‐cycle engine and do work. A brief analysis on the utility of liquid nitrogen for doing work shows some surprising results in comparison with lead/acid batteries. The specific energy (the work per unit mass) is found to be higher for liquid nitrogen while the energy cost is found to be about an order of magnitude lower.

ISSN:0002-9505    

DOI:10.1119/1.18195

出版商:American Association of Physics Teachers    

年代:1996

数据来源: AIP

摘要:

Generalization of the laws of dynamics to noninertial frames is based on the kinematic transformation formula for accelerations relative to different frames. A new approach is proposed to treat this problem. The relationship between accelerations relating to different frames of referenceRandR′ is stated in the forma=a′+aP+2ω×v′ which is derived in this paper from fundamental geometrical properties, without referring to any actual coordinate system. HereaPis the ‘‘conveyer acceleration,’’ that is the acceleration (relative toR) of the pointPofR′ where the material point is found at the given instant. The conventional detailed transformation formula follows then from the well‐known kinematic formula of rigid bodies,afterhaving chosen a translational point inR′ serving as the origin of thecoordinatesystemK′:aP=a0+ω×(ω×r′)+β×r′.

ISSN:0002-9505    

DOI:10.1119/1.18196

出版商:American Association of Physics Teachers    

年代:1996

数据来源: AIP

摘要:

A simple example of a four‐stroke engine operated in finite‐time is analyzed. The working medium consists of noninteracting two‐level systems or harmonic oscillators. The cycle of operation is analogous to a four‐strokeOttocycle. The only source of irreversibility is due to the finite rate of heat transfer between the working medium and the cold and hot baths. The dynamics of the working medium is governed by a master equation. The engine is shown to settle to a stable limit cycle forgivencontact periods with the hot and cold baths. The operation of the engine is analyzed subject to a fixed cycle time. The time allocation between the hot and cold branches that maximizes the work output is considered. Analytical results are obtained when the relaxation is very slow, very fast, or when the relaxation rates along the hot and cold branches are equal. Numerical results are presented for the general case. A maximization of the power with respect to the cycle time leads to a finite optimal cycling frequency provided the adiabatic branches are allotted finite durations.

ISSN:0002-9505    

DOI:10.1119/1.18197

出版商:American Association of Physics Teachers    

年代:1996

数据来源: AIP

摘要:

It is shown that, for a relativistic Doppler effect to depend on one‐dimensional source and observer motions only through their relative velocity, then the wave speed must equal the speed of light in vacuum or satisfy the dispersion relation for a collisionless electron gas. The three‐dimensional case is briefly examined, showing that the same results apply. The appropriate Doppler formula is derived, showing the explicit dependence upon the relative velocity; the one‐dimensional and vacuum optical cases are readily deduced as corollaries.

ISSN:0002-9505    

DOI:10.1119/1.18198

出版商:American Association of Physics Teachers    

年代:1996

数据来源: AIP

摘要:

The basic properties of the relativistic string, including its simplest modes of motion, are shown to be derivable in an elementary manner directly from the postulate of constant tension. The full set of equations of motion can be derived from the same principle by employing slightly more advanced mathematical concepts. Finally a heuristic derivation of the Nambu–Goto action is presented.

ISSN:0002-9505    

DOI:10.1119/1.18199

出版商:American Association of Physics Teachers    

年代:1996

数据来源: AIP

ISSN:0002-9505    

DOI:10.1119/1.18200

出版商:American Association of Physics Teachers    

年代:1996

数据来源: AIP

ISSN:0002-9505    

DOI:10.1119/1.18201

出版商:American Association of Physics Teachers    

年代:1996

数据来源: AIP

ISSN:0002-9505    

DOI:10.1119/1.18202

出版商:American Association of Physics Teachers    

年代:1996

数据来源: AIP