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A calibration curve and table are presented for deriving approximate magnitudes from the UKSTU J-survey.

Measurements of the magnetocrystalline anisotropy constants have been made on a single crystal of gadolinium using a torque magnetometer. The apparatus used is briefly described and the application of corrections for lack of saturation and for a paramagnetic component are explained. Measurements have been made between 37.5 °K and 315 °K and it is found that three constants are required to represent the results. It is shown that at temperatures greater than 240 °K the easy direction is the hexagonal axis. Below this temperature the easy direction lies on a cone whose axis is the c axis, and the variation of cone angle with temperature is calculated from the values of the anisotropy constants.

A simple theoretical analysis of the magnitude of bombardment conductivity pulses produced in a Schottky type exhaustion barrier is carried out. For the energetic particles incident on the crystal normal to the field direction, the variations of pulse size with position of incidence in the barrier and with applied voltage are found. The case of incidence parallel to the field direction is also considered. Comparison with experiment for zinc sulphide crystals shows good agreement with the predicted results, and values of the electron lifetime and donor concentration are obtained.

The APN-1 unit is a low cost piece of equipment available from many of the dealers handling surplus electronic devices. It is normally used as a radio altimeter in which a frequency modulated 440 MHz signal is transmitted from the aircraft and received after reflection from the ground. The phase of the modulation is then compared with a direct signal by determining the maximum beat frequency on a rate-meter. It is possible to use the unit in its original form as a means of introducing students to practical aspects of frequency modulation. Furthermore it can be used for a straightforward method of determining the effective dielectric constant of the dielectric spacing of a coaxial cable or for a complementary experiment to find the velocity of propagation down the line.

A stage micrometer is illuminated from below through an almost closed substage iris diaphragm and brought to focus with a * 10 objective. When the eyepiece of the microscope is removed the light distribution in the back focal plane of the objective is seen to be a diffraction pattern of light spots. Selected orders of this pattern are then obscured by placing suitable masks in the back of the objective and the effects on the final images are examined photographically. The nature of these images is then observed qualitatively and by inference one is led to an analysis in terms of the Fourier component gratings.

The Lecher wire experiment found in undergraduate laboratories is usually limited to the observation of the voltage distribution for open and short circuit terminations and to the determination of wavelength. With some modification to the usual arrangement the scope of the experiment may be extended to show the effects of resistive and reactive terminations and to the measurement of unknown complex impedances. An experiment in which this is achieved is described.

Spin echo measurements of the ⁵⁹Co nuclear resonance in GdCo ₂ have revealed a rapid decay of the spin-echo amplitude with temperature up to 40 K followed by a further growth up to 79 K and subsequent decay above this temperature.