TY - JOUR A1 - Vollmer, Michael A1 - Möllmann, Klaus-Peter T1 - Infrarotkameras: es gibt mehr zu sehen als unsere Augen wahrnehmen JF - In: Naturwissensschaftliche Rundschau 61 (2008) 11, 557—565 Y1 - 2008 SP - 557 EP - 565 ER - TY - JOUR A1 - Vollmer, Michael A1 - Möllmann, Klaus-Peter A1 - Arnold, Frank T1 - Ins eigene Segel blasen. Münchhausen-Effekt und Schubumkehr JF - In: Physik in unserer Zeit 39 (2008) 5, 241-245 N2 - Kann man sich mit seinem Segelboot fortbewegen, indem man ins eigene Segel bläst? Der Impulssatz erlaubt diesen an Münchhausen erinnernden Effekt. Das demonstriert ein vereinfachtes Gedankenexperiment, bei dem der Segler durch den Werfer eines Balls und das Segel durch eine starre Wand ersetzt wird. Allerdings ergibt die naive Theorie, die Luftmoleküle als ballähnliche Korpuskeln auffasst, einen zu hohen Impuls des reflektierten Luftstroms. Eine realistische Beschreibung liefert die moderne Strömungstheorie. Ihre Resultate sind experimentell erfolgreich umsetzbar. Technisch angewendet wird das Prinzip in der Schubumkehr von Flugzeugtriebwerken. Y1 - 2008 U6 - https://doi.org/10.1002/piuz.200801172 SP - 241 EP - 245 ER - TY - CHAP A1 - Chiaverina, Chris A1 - Vollmer, Michael T1 - Learning physics from the experiments T2 - In: Informal learning and public understanding of physics : third international GIREP seminar 2005 ; selected contributions ; [5 - 9 September 2005, Ljubljana, Slovenia] / ed.: Gorazd Planinšič ... Ljubljana : Faculty of Mathematics and Physics, 2006 Y1 - 2006 PB - Faculty of Mathematics and Physics CY - Ljubljana ER - TY - JOUR A1 - Vollmer, Michael T1 - Diffraction revisited : position of diffraction spots upon rotation of a transmission grating JF - In: Physics education 40 (2005), 562-565 Y1 - 2005 SP - 562 EP - 565 ER - TY - JOUR A1 - Vollmer, Michael T1 - Hot gases : transition from line spectra to thermal radiation JF - In: American journal of physics 73 (2005), 215-223 N2 - The question of how the line spectrum of atoms is transformed into the continuous spectrum of thermal radiation of a gas by repeated absorption and emission of photons is addressed. We consider a simple model of a hydrogen-like gas in thermal equilibrium where only the Lyman-α transition is allowed and calculate the spectra for increasing thickness of the gas. The transition from line spectra for optically thin samples to the spectra of thermal radiation for optically thick samples is demonstrated. We estimate the emissivities for hot gases and study the line width of spectral lines due to self-absorption processes. Y1 - 2005 SP - 215 EP - 223 ER - TY - JOUR A1 - Cowley, L. A1 - Laven, Ph. A1 - Vollmer, Michael T1 - Rings around sun and moon : coronae and diffraction JF - In: Physics Education 40 (2005) 1, 51-59 Y1 - 2005 SP - 51 EP - 59 ER - TY - JOUR A1 - Vollmer, Michael A1 - Möllmann, Klaus-Peter A1 - Karstädt, Detlef T1 - Microwave oven experiments with metals and light sources JF - In: Physics Education 39 (2004), 500-508 N2 - Don't put metal objects in the microwave' is common safety advice. But why? Here we describe demonstration experiments involving placing household metallic objects in a microwave oven. These allow a better understanding of the interaction of microwaves with materials. Light bulbs and discharge lamps can also be used in instructive demonstrations. Y1 - 2004 SP - 500 EP - 508 ER - TY - JOUR A1 - Vollmer, Michael A1 - Möllmann, Klaus-Peter A1 - Karstädt, Detlef T1 - More experiments with microwave ovens JF - In: Physics education 39 (2004) 4, 346 – 351 N2 - Microwave ovens can be used to perform exciting demonstrations that illustrate a variety of physics topics. Experiments discussed here show superheating, visualize the inhomogeneous heating that takes place in a microwave and also show how to use a mobile phone to detect radiation leaking from the oven. Finally eggs can give some spectacular (though messy) explosions. In all cases please note the safety advice given. Y1 - 2004 SP - 346 EP - 351 ER - TY - JOUR A1 - Parker, Kerry A1 - Vollmer, Michael T1 - Bad food and good physics : the development of domestic microwave cookery JF - In: Physics Education 39 (2004) 1, 82-90 N2 - This article forms the second of two papers on the subject of microwave cookers. In the first paper Michael Vollmer describes the physics behind the production of microwaves in the magnetron of the oven, the waveguide and the interaction between the microwaves and the food. This article looks at the physics of cooking, and how the appliance and the food industries have developed products which are now part of many of our students' lifestyles. We include many interesting demonstrations that illustrate this history and which could be used to teach many principles of physics. Y1 - 2004 SP - 82 EP - 90 ER - TY - JOUR A1 - Vollmer, Michael T1 - Physics of the microwave oven JF - In: Physics education 39 (2004) 1, 74-81 N2 - This is the first of two articles about the physics of microwave ovens. This article deals with the generation of microwaves in the oven and includes the operation of the magnetrons, waveguides and standing waves in resonant cavities. It then considers the absorption of microwaves by foods, discussing the dielectric relaxation of water, penetration depths of electromagnetic waves in matter and, in considering the possible chemical changes during the microwave heating, multi-photon ionization or dissociation. Y1 - 2004 SP - 74 EP - 81 ER -