Nitrate is a crucial parameter for assessing water quality, owing to its dual function in ecological systems. These functions can be beneficial or detrimental depending on whether nitrate concentrations are low or high, respectively. The ultraviolet spectrophotometric method (standard as 4500-NO[subscript 3]--B) is a classic method for determining…

Introduces the method of ray tracing to analyze the refraction or reflection of real or virtual images from multiple optical devices. Discusses ray-tracing techniques for locating images using convex and concave lenses or mirrors. (MDH)

A common misconception among students setting up force-acceleration problems is to think of the expression "mass times acceleration" as a force itself. Presents a new formula to express the relationship between force, mass, and acceleration, and discusses its benefits. (MDH)

Introduces a new sign convention for the object and image distances involving mirrors and lenses. Proposes that the method is easier for students to understand and remember and that it helps clarify the physics concepts involved. (MDH)

Establishes a rationale for teaching population genetics to students and inservice biology teachers. Suggests strategies for introducing students to the Hardy-Weinberg principle. (MDH)

Described is a graduate level engineering course on functional analysis offered at Purdue University. The course restricts itself to linear problems, specifically analysis of linear operators on vector spaces. Key applications in the course demonstrating the utility of abstract formulations are presented. (BT)

Discusses solutions to the problem of maximizing the range of a projectile. Presents three references that solve the problem with and without the use of calculus. Offers a fourth solution suitable for introductory physics courses that relies more on trigonometry and the geometry of the problem. (MDH)

Calculates an approximation to Avagadro's number for one mole of water by assuming the mole to be in cubical form and then halving the cube three times, thereby doubling the surface area of the original cube. The calculations are derived from the work necessary to perform these divisions. Presents calculated values for several liquids. (MDH)

Discusses formal-economical/epistemic-powerful features of physics formulas: the first puts constructs in logical relations to each other, reducing constructs to symbols; the second describes the correspondence which links the construct to natural events. Implications of the dual nature of formulas (considered as efficient learning tools) for…

Describes the construction of a wave generator used to review the algebraic relationships of wave motion. Students calculate and measure the weight needed to create tension to generate standing waves at the first eight harmonics. (MDH)

Presents an activity in which students construct model hot air balloons to introduce the concepts of convection current, the principles of Charles' gas law, and three-dimensional geometric shapes. Provides construction and launching instructions. (MDH)

Describes the modern hot-air balloon and the physics of ballooning. Proposes that students construct their own hot-air balloon and presents an experiment calculating the time needed for a balloon to rise to the ceiling of a gymnasium. (MDH)

Suggests an approach to understanding the integrals associated with teaching electricity and magnetism at the college level. Categorizes integrals that are commonly used, explains the significance of paired usage and presents a method for introducing concepts. Provides a review of symbols and for integrals in college textbooks. (CW)

Describes two simple methods of error analysis: (1) combining errors in the measured quantities; and (2) calculating the error or uncertainty in the slope of a straight-line graph. Discusses significance of the error in the comparison of experimental results with some known value. (MDH)

Presents a framework for teachers to use the thermodynamic system of popping corn to generate student interest. Examines the popping mechanism and the role of steam in, the heat required during, and the energy efficiency of the popping process. (MDH)