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So weit das Auge trägt
(2023)
Sichtweiten in der Atmosphäre reichen von wenigen Metern im Nebel bis zu einigen hundert Kilometern bei extrem guten Fernsichtbedingungen. Die zugrundeliegende Physik geht vom Wahrnehmungskontrast aus. Dieser ändert sich mit der Entfernung entlang der Sichtlinie zwischen Objekt und Auge aufgrund von Lichtstreuung und Absorption an den Bestandteilen der Atmosphäre. Dazu kommt bei der Fernsicht die Refraktion, die es erlaubt, auch über den durch die Kugelform der Erde geometrisch bedingten Horizont hinaus zu sehen.
Gefrierende Gewässer
(2021)
Wenn Licht die Biege macht
(2020)
Fata Morgana im Wasserbecken
(2020)
Freezing of lakes is described using a simplified one-dimensional model, which gives ice thickness, ice growth rates, and ice surface temperature as a function of time. Model data for a specific lake with known meteorological conditions are compared to estimated ice thickness using a simple optical method. Finally, more advanced potential students projects are briefly discussed and results of a numerical solution are compared to the simplified model.
Water can exhibit many different colors due to a variety of physical properties. Here, we focus on some observable colors within very pure freshwater. We only treat the absorption of light due to electronic and ro-vibrational excitations and scattering due to refractive index fluctuations of the water and the respective consequences for the appearance of colors.
Manche mögen‘s kochend heiß
(2019)
Und sie dreht sich doch …
(2018)
Direct speed of sound measurement within the atmosphere during a national holiday in New Zealand
(2018)
Infrared Yellowstone
(2017)
Und es werde Feuer
(2017)
Und es werde Feuer
(2017)
Infrared Thermal Imaging
(2017)
Abstract
Stehaufkreisel sind faszinierende physikalische Spielzeuge, die scheinbar die Schwerkraft auszutricksen vermögen: Nach anfänglicher Rotation drehen sie sich so um, dass sie schließlich auf der früheren Spitze rotieren. Hochgeschwindigkeits-Videos ermöglichen es, die komplizierten mathematischen Lösungen ihrer Bewegung experimentell zu überprüfen.
Abstract
The brilliant visible colors of various hot springs and pools in Yellowstone National Park are explained with a combination of scattering from the water and from microbial mats that coat the bottoms of these thermal features. A simple 1D radiative transfer model was used to simulate the colors recorded in visible photographs and the spectrum of light making up these colors. The model includes attenuation in water by absorption and molecular scattering as well as reflection characteristics of the microbial mats and surface reflection of the water. Pool geometries are simulated as simple rough cones scaled to have depths and widths that match published data. Thermal images are also used to record the spatial distribution of water skin temperature. The measurements and simulations confirm that colors observed from shallow-water features arise primarily from the spectral properties of the microbial mat, which is related to the water temperature, while colors observed from deeper water arise primarily from the wavelength-dependent absorption and scattering in the water.