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School-based assessment of science students' practical skills has two important roles-as a complement to written papers in public examinations and as a catalyst for enriching the science curriculum in schools. This article describes a quantitative study of the concerns chemistry and biology teachers experience as they engage in the process of implementation of a school-based assessment scheme for practical work. A 23-item questionnaire was developed to measure five categories of teacher concern: evaluation, information, management, consequence and refocusing. The nature of each category of teacher concern is discussed in relation to innovation adoption and implementation. Data were collected from 400 chemistry and 412 biology teachers in Hong Kong. Teachers' information and management concerns lessened in intensity when they became experienced users of a school-based assessment scheme. However, teaching experience alone could not motivate teachers to think more about the impact of school-based assessment on student learning, their professional development in student assessment and the possible refinements in their school-based assessment scheme. Concerns-based interventions are suggested to help teachers grow professionally.

We examine the structure of five Chinese magic mirror replicas using a special imaging technique developed by the authors. All mirrors are found to have a two-layered structure. The reflecting surface that gives rise to a projected magic pattern on the screen is hidden under a polished half-reflecting top layer. An alternative method of making the magic mirror using ancient technology has been proposed. Finally, we suggest a simple method of reconstructing a mirror replica in the laboratory.

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The speed of light is measured using a laser pointer with adjustable focus as the signal carrier, a signal generator to modulate the light beam and a student oscilloscope to detect the phase shift. Factors that may affect the phase of the final CRO trace are discussed. To avoid phase changes introduced by stray reactive components in long cables and the distortion of the waveform in the transmission process, the optical path difference is obtained by moving only a reflecting mirror, and the signal amplitude is kept constant with the mirror in two different positions.