Results 1 - 9 of 9
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[en] Measuring flats in the horizontal posture with interferometers is analyzed in detail, taking into account the sag produced by gravity. A mathematical expression of the bending is provided for a plate supported at three unevenly spaced locations along the edge. It is shown that the azimuthal terms of the deformation can be recovered from a three-flat measuring procedure, while the pure radial terms can only be estimated. The effectiveness of the iterative algorithm for data processing is also demonstrated. Experimental comparison on a set of three flats in horizontal and upright posture is provided
[en] The observation of peculiar light patterns produced by reflection from a water surface perturbed by falling droplets is reported. The phenomenon is analysed in some detail, with a simplified model of a surface wave packet. A simple experiment reproducing the phenomenon in the laboratory is presented, also showing evidence of pattern distortions that were not reported before. An account is given in terms of the vector nature of the law of reflection, also referring to the time constant of the eye
[en] A phase-shift interferometry experiment is proposed, working on a Twyman-Green optical configuration with additional polarization components. A guideline is provided to modern phase-shift interferometry, using concepts and laboratory equipment at the level of undergraduate optics courses
[en] An account of peculiar light patterns produced by reflection in a pool under falling rain droplets was recently reported by Molesini and Vannoni (2008 Eur. J. Phys. 29 403-11). The mathematical approach, however, only covered the case of a symmetrical location of a light source and the observer's eyes with respect to the vertical of the falling droplet. Extending such an account to asymmetrical configurations, a general solution for the reflection trails that are observed on the pool surface is presented.
[en] The implementation of a modern game-console controller as a data acquisition interface for physics experiments is discussed. The investigated controller is equipped with three perpendicular accelerometers and a built-in infrared camera to evaluate its own relative position. A pendulum experiment is realized as a demonstration of the proposed approach
[en] Light from a rough sample surface illuminated with a laser consists of a speckle pattern. If the surface evolves with time, the pattern becomes dynamic, following the activity of the sample. This phenomenon is used both in research and in industry to monitor processes and systems that change with time. The measuring equipment generally includes high-performance CCD cameras and other expensive devices. Based on the same principle, here we describe a simplified approach where components and devices commonly available in undergraduate physics laboratories are instead used. The technique is described in detail, also reviewing the basic properties of speckle fields. Examples of the application are given, and suggestions for further investigation are provided
[en] The use of a spectrometer to measure the refractive index of a prism glass sample in the visible and near-infrared regions at cryogenic temperature is reported. The details of the measuring cell and the experimental apparatus are provided, and a specific data reduction procedure based on ray tracing is introduced. Demonstrative results on a BK7 prism sample in a temperature range from 105 to 293 K and wavelength from 480 to 894 nm are presented. The measurement uncertainty is 3 × 10−5 (2σ)
[en] The Shack interferometer is a simple and effective device to test optical surfaces in reflection and optical systems in transmission. An essential setup on a reduced scale with a minimum number of components is presented, suited to gain familiarity and practice with optical testing in a laboratory course for undergraduate students. The basic layout and the optics principles are discussed, fringe processing is detailed and the calculation of the point spread function in the presence of typical aberrations is demonstrated. (paper)
[en] We present experimental results and numerical finite element analysis to describe surface swelling due to the creation of buried graphite-like inclusions in diamond substrates subjected to MeV ion implantation. Numerical predictions are compared to experimental data for MeV proton and helium implantations, performed with scanning ion microbeams. Swelling values are measured with white-light interferometric profilometry in both cases. Simulations are based on a model which accounts for the through-the-thickness variation of mechanical parameters in the material, as a function of ion type, fluence and energy. Surface deformation profiles and internal stress distributions are analyzed and numerical results are seen to adequately fit experimental data. Results allow us to draw conclusions on structural damage mechanisms in diamond for different MeV ion implantations.