Crystals are beautiful structures--yet they occur naturally in dirty and remote places. In the inquiry-based activity described here, students will enjoy the process of creating their own crystals and using microscopes to examine them. It demonstrates the process of mineral concentration and deposition. Upon completing this activity, students…

The International Young Physicists' Tournament (IYPT) is a worldwide, annual competition for secondary school students. This is our solution to problem number 10, "The Kaye effect", as presented in the final round of the 21st IYPT in Trogir, Croatia. The Kaye effect occurs when a thin stream of shampoo or a different adequate non-Newtonian liquid…

A problem-based approach to the teaching of mechanical wave propagation, focused on observation and measurement of wave properties in solids and on modelling of these properties, is presented. In particular, some experimental results, originally aimed at measuring the propagation speed of sound waves in metallic rods, are used in order to deepen…

Employment of a data-acquisition system for data collection and calculations makes experiments with antennas more convenient and less time consuming. The determined directional patterns of the dipole antennas of different lengths are in reasonable agreement with theory. The enhancement of the signal by using a reflector is demonstrated, and a…

In the exciting, "out of this world" activity described here, students measure the Earth using meter sticks while measuring their shadows in two distant locations. To obtain the size of the Earth, students discover the connection between the measurements of the shadows and a model of the spherical Earth following the method developed by…

Bacteriocins, bacteriocidal proteins produced by bacteria, have a very restricted killing range. In this exercise each student isolates an environmental "Enterococcus spp." culture using selective media and then evaluates it for bacteriocin activity against "Enterococcus" strains isolated by classmates.

We present an experimental method to obtain the effective mass of an unloaded oscillating spring. We measure the period "T"("n") of the partial springs that result when hanging "n" of the total "N" coils of a given spring. Data are correlated with the expectation of a simple model for "T"("n") that takes into account the effective mass of the…

In the 1930s physicists were confronted by two conflicting values for the charge of the electron as measured with great precision by two different methods. Could it be that there are two kinds of (negative) electrons, differing in charge by a fraction of a percent? The experiments were reconciled when a small systematic error in one of the…

Once an intriguing topological novelty known only to mathematicians, the Mobius strip has become a source of fascination and inspiration to the layperson and artist alike. Principal among its features are the two strange properties that the Mobius strip is a surface with only one side and one edge. A Mobius strip is readily formed by taking a long…

This article reports that a quiet debate is unfolding over proposals to tinker with No Child Left Behind Act's (NCLB) definition of what constitutes "scientifically based research" in education while other ideas for revamping it are taking center stage. Sprinkled through the federal education statute more than 100 times, the references…

The refraction of a light ray by a homogeneous, isotropic and non-dispersive transparent material half-space in uniform rectilinear motion is investigated theoretically. The approach is an amalgamation of the original Fermat's principle and the fact that an isotropic optical medium at rest becomes optically anisotropic in a frame where the medium…

In this work, the oscillations of a homogeneous string fixed at both ends, and loaded with a finite number of masses, are studied. Through a simple device, the cases with one and two concentrated masses are analysed in detail. The normal modes are observed and the corresponding frequencies are recorded. The experimental results and the solutions…

A study was conducted to examine the structural order-disorder transformation promoted by controlled heat treatment using X-ray diffraction technique (XRD) and photoluminescence (PL) techniques as tools to monitor the degree of structural order. The experiment was observed to be versatile and easily achieved with low cost which allowed producing…

A microscale classroom demonstration of the paramagnetic behavior of various samples of liquid oxygen with neodymium magnet is being presented. The experiment should be done with extreme caution, as liquid oxygen reacts violently with organic matters.

The study describes and compares the size-dependent optical properties of organic dyes with those of semiconductor nanocrystals or quantum dots (QDs). The analysis shows that mixtures of QDs contain emission colors that are sum of the individual QD components.