Students can be taught to appreciate the wealth of information that can be efficiently presented in a mathematical formula, and get a glimpse at a simplifying approximation plus a mathematical use of symmetry. (DF)

Maintains the concept of diffraction becomes difficult to understand if the terminology remains inconsistent in its present form. Two terms, diffraction and interference, are used for the same phenomenon in different situations. Mathematical treatment is presented to understand these concepts clearly. (PS)

Describes a graphical method for representing image formation in lenses and mirrors. (MLH)

Discusses the work and energy involved in walking on horizontal surfaces. (MLH)

Correspondence of Benjamin Franklin provides authenticity to a historical account of early work in the field of lightning. Present-day theories concerning the formation and propagation of lightning are expressed and photographic evidence provided. (CP)

Photographs show three simple demonstrations of deceptive centers of gravity. (CP)

The circular motion observed when water drains into a smooth opening is analyzed. This action, as well as cycloidal atmospheric motion, is explained as the result of rotation of the coordinate system. (CP)

In the first part of this article, brief reviews were given of the atomic-scale mechanisms by which crystalline solids deform and the nature of the interface between such solids and their environment. In this part, the mechanisms of a representative range of surface and environment sensitive mechanical phenomena are explained. (Author/CP)

Describes a physics experiment in single and multiple slit diffraction and interference phenomena that illustrates the existence of diffraction gratings in many common objects. (MLH)