Table of contents

Compact discs have uses other than accurate recording of sound. The coding on the shiny surface of a disc allows simple but informative diffraction experiments.

The compact disc provides an excellent example of the application of basic physics principles, from the derivation of the signal by interference to the dependence of audio frequency response and playing time on the optical wavelength used.

This article is the first part of one of the keynote addresses presented at the 1991 Pan-American Science conference in Venezuela. The second part (`Risks of radioactivity') is the March 1993 issue and the final part (`Public risks due to nuclear Industry') in the May issue.

Computer-controlled collisions between two pendulums are described for use as a laboratory experiment. A force transducer provides a detailed description of the collision in time.

This article presents research aimed at designing a strategy to help students aged 11 to 12 years understand the concept of speed. In our approach the work of students is based on experimental activities integrated with Logo programming.

The amplitude-dependent period and the law of motion of a simple but very instructive nonlinear (cube-law) mechanical oscillator are studied both analytically and numerically. Special attention is paid to the application of energy conservation and to the relevant numerical analysis since these would be appropriate to an introductory physics course.

Processes in the ocean or atmosphere can be explained using physics, and the necessary tools of fluid dynamics, such as Reynolds number, are introduced here. Particular attention to paid to eddies formed in the wake of obstacles.

The flow around an obstacle can be visualized using relatively simple and cheap apparatus. Such an experiment is described here including photographs showing eddies.

Many of the difficulties students have in the understanding of geometrical optics are related to their personal experience of `seeing' and its coupling with an incomplete understanding of the formal representations used in this domain. This article explains why the incorporation of a functional model of the eye from the very beginning of the optics course may lead to a better understanding of the domain.

Solar energy was introduced at the undergraduate level in the Physics Department of the University of the West Indies (Trinidad) some ten years ago as undergraduate projects. The results have been most encouraging, and some aspects of those results are presented here.

Elementary particles and philosophy of scienceEric Scerri Department of History and Philosophy of Science, King's College, London, UK

Muscle forces and Newton's third lawA H Bachman Physics Department, City College of New York, NY 10031, USA

Science for the year 2000Martin Brown 122 Bryansburn Road, Bangor, County Down BT20 3RG, UK

More examples of the harmonic meanA Tan Department of Physics, Alabama A & M University, Normal, AL 35762, USA

Science SATsD L Richards 16 Purcell Crescent, London SW6 7PB, UK