The aim of this study is to analyse the effect of tasks on the detection of explanation obstacles when secondary school students read scientific texts. Students were instructed to read short passages under different task conditions, and to ask questions if necessary. Obstacle detection was operationalised in terms of the type of questions asked by…

Experiences and experiments with mirrors will spark pupils' imaginations while providing insights into the nature and behavior of light. (Author/DF)

Reviews the Hafele-Keating experiment on relativistic changes in eastward and westward moving cesium atomic clocks. Recommends the use of the Sagnac effect to remove the east-west time asymmetry and of the general-relativistic effect to elucidate the clock-rate changes. (CC)

In this simple experiment for an undergraduate laboratory a laser beam is passed through the mixing zone of two liquids with different refractive indices. The spatial variation of the refractive index, at different times during the mixing, can be determined from the observed deflection of the beam. (Author)

This article describes three connected projects in physics: (1) a very successful course at the university level; (2) a collection of several thousand multimedia materials, its status and evaluation, and its dissemination; and (3) Web experiments--experiments that can be operated remotely from a distance via the Internet. (Contains 4 tables and 10…