Photoplethysmography (PPG) is a technique that uses light to noninvasively obtain a volumetric measurement of an organ with each cardiac cycle. A PPG-based system emits monochromatic light through the skin and measures the fraction of the light power which is transmitted through a vascular tissue and detected by a photodetector. Part of thereby transmitted light power is modulated by the vascul...

Johann Heinrich Lambert is best known for his work in physics. The law of Bouguer-Lambert-Beer on the absorbtion of light may be his most famous achievement. He is also well known in mathematics, for example for his proof of π and e being irrational numbers, for his work on non-additive probabilities and for his contribution to non-Euclidean geometry. He worked on numerous problems of natural s...

Abstract The linear relationship between optical absorbance and the concentration of analytes—as postulated by Beer-Lambert law—is one fundamental assumptions that much spectroscopy literature is explicitly or implicitly based upon. common use regression models such as principal component partial least squares exemplifies how linearity assumption upheld in practical applications. However, also ...

A dual-function student-crafted instrument is described as part of a laboratory activity aimed to teach both the principles and practical aspects absorption spectroscopy secondary introductory undergraduate students. Using minimal changes in an arrangement that based on interlocking bricks low-cost components, fluorometer photometer have been constructed. The former demonstrates Beer–Lambert la...

Solute transport in fractured rocks is of major interest in many applications: geothermal energy production, petroleum industry, ground water management. This work focuses on a dispersion experiment performed with a transparent replica of a real fracture. The local aperture map was extracted using the well-known Beer-Lambert law, which shows a very heterogeneous medium. The hydrodynamic apertur...

The celebrated Lambert-Beer law of light absorption in photochromic media is only valid at low intensities of incident light and low concentration of chromophore. Here we address the generic problem of photoabsorption dynamics, experimentally studying the case of azobenzene isomerization. We show that the nonlinear regime is very common and easy to achieve in many practical situations, especial...