We were recently hired to produce a series of animation clips for Science Photo Library, as part of their educational animation licensing arm (www.sciencephoto.com). Here are our favourite five stock clips! Clip 1 ) Rutherford scattering (gold foil experiment). Animation depicting the actual outcome of Rutherford’s 1909 experiment to probe the structure of an atom. At left, a source of alpha radiation is firing alpha particles (helium nuclei) at a thin sheet of gold foil (down centre). Most of the alpha particles pass straight through the foil, as was expected, but some deviate by large angles, even bouncing back at the source. The inset shows a close-up of a gold atom, revealing that its positive charge (red) is tightly concentrated in a small, dense nucleus, with the negative electrons (blue) a relatively long way from it. This demonstration led to the downfall of the prevailing “plum pudding” model of the atom, which postulated that the electrons were studded randomly in a diffuse cloud of positive charge.; Clip 2 ) Magnetic and electric fields. A clip showing how electricity and magnetism are connected (via the right-hand rule). Animation showing the magnetic fields generated around a conducting wire and a coil of wire (solenoid). When the wire is coiled into a spiral tube, it is called a solenoid, and has a field similar to that of a bar magnet. A right-hand rule still applies: when the fingers are coiled in the direction of the current, the thumb points to the north pole of the solenoid.; Clip 3 ) Animation of the electric field lines between two point charges. By convention field lines are shown with arrows indicating the direction of movement of a point positive charge placed in the field. Around a negative charge this is symmetrically towards it, and away from a positive charge. When identical point charges are placed near each other, their fields repel and do not touch. When opposite charges are next to each other, their field lines join and they attract each other.; Clip 4 ) Charged particles in a magnetic field, and a cyclotron. Alpha, beta and gamma radiation in a magnetic field, showing the paths taken through the field. A cyclotron is a type of particle accelerator. A charged particle, here a hydrogen nucleus (proton), is injected at the centre of two semicircular electrodes called dees. A magnetic field (arrows) is established perpendicular to the plane of the dees. This causes the particle to move in a circular path. The voltage across the dees is reversed each time the particle is in one of the dees, constantly accelerating it towards the other. As its time in each dee is constant, the larger its path the faster it moves, and the particle spirals outwards. When it reaches the desired speed, it exits the cyclotron, and at this high energy level it is able to convert 18O to the useful radioactive tracer 18F.; Clip 5 ) Reflection, refraction and diffraction of light. Animation of the principle of reflection, showing a beam of light reflecting from a mirror. In reflection, the angle of incidence (red) is equal to the angle of reflection (green), whatever the angle. In refraction, the change in direction of a wave due to a change of the medium through which it is travelling. When a beam of light passes into another medium at an angle, it deflects by an amount proportional to the difference in the speed of light between the materials, a figure called its refractive index. If it hits the surface at 90 degrees, there is no deflection but it still slows down. Snell’s law states that the sine of the angle of incidence (red) multiplied by the refractive index of the first material in equal to the sine of the angle of refraction (green) times the refractive index of the second material. The equivalent occurs when the beam leaves the material, exiting on a parallel path to the one on which it entered. The double-slit experiment demonstrates the wave behaviour of light, showing the interference pattern produced. When light passes through a double slit, it diffracts and spreads out, and interferes with the light from the adjacent slit. This leads to alternating regions where the interfering waves either cancel each other out or amplify each other, leading to a pattern of dark and light bands. For a given separation of the slits, the width of the bands depends on the wavelength of the light: longer wavelengths produce wider bands, and they are seen to narrow when the colour changes from long wavelength red to short wavelength violet.; Science Photo Library provides licensing of striking specialist science imagery, with more than 350,000 images and 20,000 clips. Please contact us for more information.