ISSN:0002-9505    

DOI:10.1119/1.19059

出版商:American Association of Physics Teachers    

年代:1998

数据来源: AIP

ISSN:0002-9505    

DOI:10.1119/1.19056

出版商:American Association of Physics Teachers    

年代:1998

数据来源: AIP

ISSN:0002-9505    

DOI:10.1119/1.19057

出版商:American Association of Physics Teachers    

年代:1998

数据来源: AIP

ISSN:0002-9505    

DOI:10.1119/1.19058

出版商:American Association of Physics Teachers    

年代:1998

数据来源: AIP

ISSN:0002-9505    

DOI:10.1119/1.19061

出版商:American Association of Physics Teachers    

年代:1998

数据来源: AIP

ISSN:0002-9505    

DOI:10.1119/1.19062

出版商:American Association of Physics Teachers    

年代:1998

数据来源: AIP

ISSN:0002-9505    

DOI:10.1119/1.19063

出版商:American Association of Physics Teachers    

年代:1998

数据来源: AIP

摘要:

We describe an experiment in nuclear-isotope mass spectroscopy, suitable for an advanced physics laboratory, which utilizes a relatively inexpensive commercial 60°-dipole residual gas analyzer. Students measure the terrestrial abundance of the isotope22Nerelative to20Neand compare this with recent measurements of this ratio in meteorites. These ratios provide clues to the astrophysical sites, astrophysical processes, and nuclear reactions which formed these isotopes. The mass spectrometer is also used as a residual gas analyzer to examine the gas composition (O2,N2,H2O,…) at various pressures in a typical vacuum system. This gives students insight into the design of vacuum apparatus including the optimal selection of components such as vacuum pumps for particular applications.

ISSN:0002-9505    

DOI:10.1119/1.19044

出版商:American Association of Physics Teachers    

年代:1998

数据来源: AIP

摘要:

An alternative approach with respect to the standard double-slit experiment is presented to introduce the wave-like behavior of electrons. This simple and pedagogical experiment requires a commercial transmission electron microscope and a ferromagnetic film transparent to electrons. It allows in addition the measurement of Planck’s constant.

ISSN:0002-9505    

DOI:10.1119/1.19045

出版商:American Association of Physics Teachers    

年代:1998

数据来源: AIP

摘要:

The history of the interplay between physics and mathematics in the theory of knots is briefly reviewed. In particular, Gauss’ original definition of the linking number in the context of electromagnetism is presented, along with analytical, algebraical, and geometrical derivations. In a modern context, the linking number appears in the first-order term in the perturbation expansion of a Wilson loop in Chern–Simons quantum field theory. New knot invariants, the Vassiliev numbers, arise in higher-order terms of the expansion, and can be written in a form which shows them to be generalizations of the linking number.

ISSN:0002-9505    

DOI:10.1119/1.19046

出版商:American Association of Physics Teachers    

年代:1998

数据来源: AIP