1968 09 00 Physics Bulletin - Vol 19 No 9 - Evans

Magazine Overview

Title: Physics Bulletin
Issue: Vol. 19, No. 9
Date: June 1968
Publisher: IOP Publishing
Country: United Kingdom
Language: English
ISSN: 0031-9112

This issue of Physics Bulletin features articles on educational assessment in physics, the technical aspects of diffraction patterns, and a brief discussion on the phenomenon of flying saucers.

Performance Assessment in Physics Education

The issue opens with an examination of the UCCA method for assessing A-level performance in physics, which awards points for grades (A=5, B=4, etc.). The author, likely referencing work by Prof. Thompson, notes that candidates scoring 9 or more points were considered strong. However, a significant number of candidates scored lower (2-8 points), with 56% of these 'poorer' candidates still being placed in university programs. The author expresses concern that many with lower scores might be discouraged from pursuing physics degrees, despite possessing latent potential. This is supported by data from the Portsmouth College of Technology, where graduates who initially had lower UCCA scores achieved high honors degrees, demonstrating that initial assessments may not fully capture a student's capability.

Interpretation of Electron Diffraction Patterns

J. G. Scane of the Physics Department, Portsmouth College of Technology, writes to clarify misconceptions regarding electron diffraction patterns, particularly in relation to CuAu alloys, as described in a previous article by Prof. H. Jones. Scane points out that describing these patterns as 'Laue photographs' and as projections of the reciprocal lattice is incorrect. He explains that Laue photographs, using 'white' x-rays, depend on the angle θ and available wavelengths to satisfy the Bragg equation (nλ = 2dsinθ), meaning spot position is dependent on θ, not d. In contrast, electron diffraction cameras use a nearly monochromatic electron beam with a much shorter wavelength. The Ewald sphere of reflexion in this context creates an almost planar section of the reciprocal lattice, which is undistorted. Scane corrects the indexing of certain spots in a described pattern, stating that reflexions from disordered CuAu should be indexed as 200 and 220, not 111 and 200, and that additional spots in ordered CuAul are correctly indexed as 110. He references Glossop and Pashley (1959) for a fuller analysis and emphasizes the importance of understanding the specific mechanism of diffraction for accurate interpretation.

In a response, H. Jones of the Department of Mathematics, Imperial College, London, acknowledges Dr J. A. Gard's correction regarding the terminology of Laue photographs and projections of the reciprocal lattice. Jones agrees that the terminological errors do not affect the interpretation of the causes of 110 splitting in CuAuII, a point also made by Dr Gard.

Flying Saucers Discussion

A brief section addresses the topic of flying saucers, prompted by an article by Prof. R. V. Jones. D. S. Evans from the Royal Observatory, Cape Province, South Africa, expresses skepticism, suggesting that belief in flying saucers is only warranted if one has observed Venus all night, implying that such sightings are likely misidentifications of known celestial bodies.

Additionally, the editorial notes that further letters from Mr P. C. W. Davies and Mr R. C. L. O'Neil contesting Prof. Jones' view on the inconclusiveness of flying saucer evidence were received but could not be published due to space limitations.

Recurring Themes and Editorial Stance

This issue highlights a recurring theme in scientific publications: the importance of accurate terminology and clear explanations of complex physical phenomena, as seen in the discussion on electron diffraction. It also touches upon the challenges in educational assessment and the potential for overlooked talent in physics. The inclusion of the 'Flying Saucers' section indicates the journal's willingness to engage with topics of public interest, even those on the fringes of mainstream scientific consensus, while maintaining a critical and evidence-based approach, as evidenced by the skeptical letter and the editorial note about other contesting viewpoints.