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We propose to reconsider the well-known experiment about the interference of white light from a thin soap film by adopting as an illuminating source the RGB triad produced by a LED projector. The interference pattern shows up in a particularly fascinating way and it contains direct, essential information about both the wave nature of light and of the physical thickness of the soap film.

Crystallography is a fascinating subject and an argument of great importance in the study of structure of matter and fundamental physics. Moreover, many characteristics of crystals, as well as other organic and inorganic substances, are analyzed with x-ray diffraction. In order to introduce at a basic level the above mentioned subjects, and also interference and diffraction of wave light, here we present some simple and new inexpensive optical experiments, analogous to the Laue diffraction of x-rays and electrons. We also propose an elementary geometric model to explain the two-dimensional pattern of diffractions by grating.

We propose the use of a smartphone based apparatus as a valuable tool for investigating the optical absorption of a material and to verify the exponential decay predicted by Beer's law. The very simple experimental activities presented here, suitable for undergraduate students, allows one to measure the material transmittance including its dependence on the incident radiation wavelength.

We propose the use of smartphone-based slow-motion video analysis techniques as a valuable tool for investigating physics concepts ruling mechanical wave propagation. The simple experimental activities presented here, suitable for both high school and undergraduate students, allows one to measure, in a simple yet rigorous way, the speed of pulses along a spring and the period of transverse standing waves generated in the same spring. These experiments can be helpful in addressing several relevant concepts about the physics of mechanical waves and in overcoming some of the typical student misconceptions in this same field.

The lifetimes of the photoluminescent compounds contained in the coating of fluorescent compact lamps are usually measured using specialised instruments, including pulsed lasers and/or spectrofluorometers. Here we discuss how some low cost apparatuses, based on the use of either sensors for the educational lab or commercial digital photo cameras, can be employed to the same aim. The experiments do not require that luminescent phosphors are hazardously extracted from the compact fluorescent lamp, that also contains mercury. We obtain lifetime measurements for specific fluorescent elements of the bulb coating, in good agreement with the known values. We also address the physical mechanisms on which fluorescence lamps are based in a simplified way, suitable for undergraduate students; and we discuss in detail the physics of the lamp switch-off by analysing the time dependent spectrum, measured through a commercial fiber-optic spectrometer. Since the experiment is not hazardous in any way, requires a simple setup up with instruments which are commonly found in educational labs, and focuses on the typical features of the exponential decay, it is suitable for being performed in the undergraduate laboratory.

We present a simple computer-aided experiment for investigating Coulomb's law of sliding friction in a classroom. It provides a way of testing the possible dependence of the friction coefficient on various parameters, such as types of materials, normal force, apparent area of contact and sliding velocity.

In this article we show how to verify that in a fluid surface or film the value of the surface tension (i.e. the free energy per unit area) does not depend on the area of the film itself. The experimental evidence discussed can be obtained extremely simply yet with great accuracy. This experiment is important in that it leads to a deeper understanding of the actual microscopic nature of the fluid state of matter and to its comparison with the solid state, as well as to a practical example of a differential (zero) measurement procedure.