Table of contents

The Harris data memory was originally conceived as a device to take recordings of varying factors in the field so that when subsequently replayed they could be correlated to biological phenomena which occurred at the same time. It was quickly realised that this basic requirement could be extended to produce a unit that would have application in all the sciences, either in its own right or with the addition of transducers to convert various physical changes to electrical changes to be recorded in the memory.

Optical fibre transmission systems are now starting to enter the telecommunications networks of western countries in place of coaxial or wire cable systems, after some ten to fifteen years' development. Research is still moving forward rapidly so that further generations of systems can be seen. The technology promises substantial cost reductions to the user when volume production is achieved. But who will benefit from this? The author attempts to explain the technology and provide some preliminary answers to the question.

The experiments described lead to a better understanding not only of the holographic method of producing images, but also of optical imaging by other optical systems. Holography may be used as an attractive means of teaching the principles of optics, especially in the newer physics courses.

Most students of physics first encounter the concept of electromagnetic energy flow associated with Poynting vector at a relatively advanced stage in their education, usually in the context of the flow of energy in electromagnetic waves. The present author draws attention to the possibility of introducing the Poynting vector concept at a much earlier, even elementary, stage, during discussion of simple d.c. circuits, which usually includes the resistive behaviour and some description of the electric and magnetic fields associated with the circuits.

One of the most attractive experiments with forced oscillations was described by Burchell (1975). He describes measurement of the logarithmic decrement as a function of damping, and of the amplitude of forced vibrations as a function of damping and of frequency. However, in common with most descriptions of mechanical systems, the examination of the phase relationship is very sketchy indeed. The present author describes a technique to simplify the measurement of the phase angle and so add to the completeness of a truly elegant experiment.

Characteristic features of routine methods of measuring refractive indices are careful preparation (including cunning in the design of the apparatus) and then a clear and often rapid measurement leading directly to the value of refractive index. Both features are present in the described simple critical-angle method of measuring the refractive index of a transparent solid. It is not as accurate as the well known spectrometer method, properly done, but is much less demanding on eyesight. Much of the necessary apparatus is likely to be already part of the normal stock in physics departments in schools. The method can form a useful introduction to methods of refractometry used in the optical industry.

An instructive experiment in the first-year undergraduate physics laboratory is the measurement of the critical potentials of helium using the 533 Teltron tube. In this experiment the student observes directly the quantum nature of the energy levels of isolated gas atoms and can construct his own simplified energy level diagram.

The authors describe and interesting piece of nuclear physics which can be carried out using a radioactive source, a NaI detector and the simple counting apparatus possessed by most universities and colleges.