In this work we propose an inexpensive laboratory practice for the laboratory of an introductory course of Physics for any grade of Sciences and Engineering, which was very well received by our students, where a smartphone (iOS, Android or Windows Phone is irrelevant) is used together with some mini magnets, similar to those that can be found in the door of our refrigerators, a 20 cm long school rule, a paper and a free application (app) for measuring the magnetic field using the magnetic fields sensor or magnetometer of the smartphone, which needs to be downloaded and installed. The apps we have used are: Magnetometer (iOS), Magnetometer Metal Detector and Physics Toolbox Magnetometer (Android). Nothing else is needed. Cost of this practice: 0 coins. The main purpose of the practice is that students determine the dependence of the component x of the magnetic field produced by different magnets (from the typical magnets that are decorated in refrigerators even with a ring magnet and spherical magnet). We have obtained that the dependency of the magnetic field with the distance is of the form x -3 , in total agreement with the theoretical analysis. The secondary objective is to apply the technique of least squares fit to obtain this exponent and the magnetic moment of the magnets, with theirs corresponding absolute error.

Personal exposure to Radiofrequency Electromagnetic Fields (RF-EMF) has increased due to the development of a society of information and the implementation of new technologies. Most studies about RF-EMF are focused on adult exposure in different microenvironments, but these studies do not usually consider places where children are exposed. We present results of measurements and analysis of personal exposure to RF-EMF at outdoor and indoor school buildings, at a Spanish school, a place where children and employees spend a significant time period and are exposed to RF-EMF. The highest exposure levels were recorded inside school buildings during the week, and around the school area during the weekend. Our measurements show that levels of RF-EMF intensity from Wi-Fi band registered around school area are affected by Wi-Fi from neighbors of residential areas. Exposure levels from Wi-Fi band and mobile phone antennas are below reference levels established by international guidelines. INDEX TERMS Radiofrequency Electromagnetic Fields (RF-EMF), Wi-Fi, personal exposure, spot measurements, outside and inside school.

In the last two decades, due to the development of the information society, the massive increase in the use of information technologies, including the connection and communication of multiple electronic devices, highlighting Wi-Fi networks, as well as the emerging technological advances of 4G and 5G (new-generation mobile phones that will use 5G), have caused a significant increase in the personal exposure to Radiofrequency Electromagnetic Fields (RF-EMF), and as a consequence, increasing discussions about the possible adverse health effects. The main objective of this study was to measure the personal exposure to radiofrequency electromagnetic fields from the Wi-Fi in the university area of German Jordanian University (GJU) and prepare georeferenced maps of the registered intensity levels and to compare them with the basic international restrictions. Spot measurements were made outside the university area at German Jordanian University. Measurements were made in the whole university area and around two buildings. Two Satimo EME SPY 140 (Brest, France) personal exposimeters were used, and the measurements were performed in the morning and afternoon, and on weekends and weekdays. The total average personal exposure to RF-EMF from the Wi-Fi band registered in the three study areas and in the four days measured was 28.82 μW/m2. The average total exposure from the Wi-Fi band registered in the ten measured points of the university area of GJU was 22.97 μW/m2, the one registered in the eight measured points of building H was 34.48 μW/m2, and the one registered in the eight points of building C was 29.00 μW/m2. The maximum average values registered in the campus of GJU are below the guidelines allowed by International Commission on Non-ionizing Radiation Protection (ICNIRP). The measurement protocol used in this work has been applied in measurements already carried out in Spain and Mexico, and it is applicable in university areas of other countries.

In modern high-NA optical scanning instruments, like scanning microscopes, the refractive-index mismatch between the sample and the immersion medium introduces a significant amount of spherical aberration when imaging deep inside the specimen, spreading out the impulse response. Since such aberration depends on the focalization depth, it is not possible to achieve a static global compensation for the whole 3D sample in scanning microscopy. Therefore a depth-variant impulse response is generated. Consequently, the design of pupil elements that increase the tolerance to this aberration is of great interest. In this paper we report a hybrid technique that provides a focal spot that remains almost invariant in the depth-scanning processing of thick samples. This invariance allows the application of 3D deconvolution techniques to that provide an improved recovery of the specimen structure when imaging thick samples.

In modern high-numerical-aperture (NA) optical scanning instruments, such as scanning microscopes, optical data storage systems, or laser trapping technology, the beam emerging from the high-NA objective focuses deeply through an interface between two media of different refractive index. Such a refractive index mismatch introduces an important amount of spherical aberration, which increases dynamically when scanning at increasing depths. This effect strongly degrades the instrument performance. Although in the past few years many different techniques have been reported to reduce the spherical aberration effect, no optimum solution has been found. Here we concentrate on a technique whose main feature is its simplicity. We refer to the use of purely absorbing beam-shaping elements, which with a minimum modification of optical architecture will allow a significant reduction of the spherical aberration effect. Specifically, we will show that an adequately designed reversed-Gaussian aperture permits the production of a focal spot whose form changes very slowly with the spherical aberration.