Snap discs made of bimetal have many technical applications as thermostats. Jumping discs are a toy version of such snap discs. Besides giving technical information, we describe physical investigations. We show especially how, through simple measurements and calculations, you can determine the initial speed (∼3.5 m s −1 ), the acceleration (∼30 000 m s −2 ) and the lower and upper snap temperature (∼31; ∼99 • C). High speed videos give even deeper insight into the jump.

We present a physically interesting toy, which is easily constructed and operated-the so-called buzzer. In spite of its simplicity, its physical analysis turns out to be rather complex. Thus, it comes as no surprise that most of its users are not familiar with the underlying physical mechanism. In this paper we propose a physical model which allows for the qualitative and quantitative description of the fundamental physical properties of the buzzer and report on the good agreement between theoretical and experimental data. The model is designed to give a basis for further simplification.

Beautiful coloured interference rings can be produced by using transparent plates such as window glass. A simple model explains this effect, which was described by Newton but has almost been forgotten. Interference colours where they are not expected The formation of interference colours is usually associated with careful experimentation, specialized illumination and small dimensions. Students do not normally expect to see this phenomenon outside the laboratory, as it is not commonly known that interference colours can be seen on transparent material such as window panes which are several millimetres thick. However, if they look at a window in the usual way they will not see any interference colours-a specific perspective is required to see the coloured rings. Interference colours similar to those produced by diffraction gratings can only be seen using thick glass within a small solid angle whose centreline is perpendicular to the plate. If the centreline combines a suitable light source with its reflection on the plate it is possible to see coloured rings concentric around the reflection.

A sticky capture thread from the spiral element of spider orb-webs is formed of almost regularly spaced droplets that surround a supporting axial fibre. From the perspective of physical optics it represents a periodic linear array of scattering elements that acts as a diffraction grating. This is a novel aspect, which is of vital importance for the understanding of the overall scattering pattern. To demonstrate its significance, we present our experimental findings and compare them with results of a simplified model.

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