The multiple-reflection photograph in Fig. 1 was taken in an elevator on board the cruise ship Norwegian Jade in March 2008. Three of the four walls of the elevator were mirrored, allowing me to see the combination of two standard arrangements of plane mirrors: two mirrors set at 90 degrees to each other and two parallel mirrors. Optical phenomena…

In principle, designing a thermometer scale is easy. The trick lies in persuading others to use your scale. The Homigrade scale is an example of a clever and useful scale that has never caught on. Students can use it as an example of how they might set up their own arbitrary temperature scales.

I have been tinkering with ultrasonic transducers once more. In earlier notes I reported on optics-like experiments performed with ultrasonics, described a number of ultrasonic interferometers, and showed how ultrasonic transducers can be used for Fourier analysis. This time I became interested in trying the technique of using two detectors in…

One of my favorite 19th century electrical scientists is Edward Weston, and one of my favorite devices for teaching the topics of electromagnetic forces and torques is the D'Arsonval galvanometer. The junction of these two topics is Weston's improved meter movement that has been used in analog meters for the past 125 years.

One of the rewards of walking up the scores of steps winding around the inside of the shaft of a lighthouse is turning inward and examining the glass optical system. This arrangement of prisms, lenses, and reflectors is used to project the light from a relatively small source in a beam that can be seen far at sea.

Discusses the conditions under which stereoscopic photographs and drawings may be produced and viewed, and which will show the results of some experimental work. (DF)

Describes several methods of executing lecture demonstrations involving the recombination of the spectrum. Groups the techniques into two general classes: bringing selected portions of the spectrum together using lenses or mirrors and blurring the colors by rapid movement or foreshortening. (JM)

Explains mechanisms of 19th-century vacuum pumps. Describes demonstrations using the pump including guinea and feather tube, aurora tube, electric egg, Gassiots cascade, air mill, bell in vacuum, density and buoyancy of air, fountain in vacuum, mercury shower, palm and bladder glasses, Bacchus demonstration, pneumatic man-lifter, and Magdeburg…

Methods and procedures are discussed for producing films such as Lissajous Figures'' and Fermat's Principle.'' (DF)

Discusses the discovery of frictional electrification in 1840, which was the basis of the nineteenth-century electrostatic generator. (MVL)

Describes ray tracing techniques and the method of virtual mirrors to locate images when using multiple mirrors. (JN)

Discusses theory of the rotating mirror, its use in measuring the velocity of the electrical signal in wires, and the velocity of light. Concludes with a description of the manometric flame apparatus developed for analyzing sound waves. (SK)

Describes demonstrations used by the nineteenth century physicists to determine if two bodies oscillating at the same acoustic frequency were in phase. (GA)

Describes method for locating images in simple and complex systems of thin lenses and spherical mirrors. The method helps students to understand differences between real and virtual images. It is helpful in discussing the human eye and the correction of imperfect vision by the use of glasses. (Author/SK)

Explains the idea that a half-length mirror is sufficient to view the whole length, regardless of distance. (GA)