@article{Vollmer2024, author = {Vollmer, Michael}, title = {Limitations of the eye and how to overcome them}, series = {Journal of Physics: Conference Series}, volume = {2750}, journal = {Journal of Physics: Conference Series}, number = {1}, doi = {10.1088/1742-6596/2750/1/012001}, pages = {1 -- 10}, year = {2024}, abstract = {Human eyes have spatial, temporal, and spectral limitations which impose constraints on our perception. With appropriate optical devices and cameras, the limitations can be easily overcome. As a consequence, a huge variety of physical phenomena can be made accessible for teaching.}, language = {en} } @article{Vollmer2025, author = {Vollmer, Michael}, title = {Nachtsicht ins All mit dem bloßen Auge: Sag mir, wie weit die Sterne steh'n}, series = {Physik in unserer Zeit}, volume = {2025}, journal = {Physik in unserer Zeit}, publisher = {Wiley}, doi = {10.1002/piuz.202501751}, pages = {2 -- 10}, year = {2025}, language = {de} } @article{Vollmer2025, author = {Vollmer, Michael}, title = {Naked eye celestial objects and phenomena: how far can we see at night?}, series = {European Journal of Physics}, volume = {46}, journal = {European Journal of Physics}, number = {3}, publisher = {IOP Science}, doi = {10.1088/1361-6404/adbf74}, pages = {18}, year = {2025}, abstract = {How far can we see with the naked eye at night? Many celestial objects like stars and galaxies as well as transient phenomena such as comets and supernovae can be observed in the night sky. We discuss the furthest distances of such objects and phenomena observable with the naked eye during the night-time for Earth-bound observers. The physics of night-time visual ranges differs from that of daytime observations because human vision shifts from cones to rods. In addition, mostly point sources are observed due to the large distances involved. Whether celestial objects and phenomena can be detected depends on the contrast of their radiation and the background sky luminance. We present a concise overview of how far we can see at night by first discussing the effects of the Earth's atmosphere. This includes attenuation of transmitted radiation as well as its role as a source of background radiation. Disregarding the attenuation of light due to interstellar and intergalactic dust, simple maximum night-time visual range estimates are based on the inverse square law, which can be easily verified by laboratory and demonstration experiments. From the respective calculations, we find that individual stars within the Milky Way galaxy of up to 15 000 light years are observable. Even further away are observable galaxies with several billion stars. The Andromeda galaxy can be observed with the naked eye at a distance of around 2.5 million light years. Similarly, the observability of supernovae also allows a visual range beyond the Milky Way galaxy. Finally, gamma ray bursts as the most energetic events in the universe are discussed concerning naked eye observations.}, language = {en} } @article{Vollmer2025, author = {Vollmer, Michael}, title = {How far can we see at day?}, series = {European Journal of Physics}, volume = {46}, journal = {European Journal of Physics}, number = {3}, publisher = {IOP Science}, doi = {10.1088/1361-6404/adc4a0}, pages = {17}, year = {2025}, abstract = {We discuss the farthest objects on Earth observable for the unaided, healthy naked eye during the daytime, i.e., the maximum visual range for observers on Earth. Visual range depends first on the properties of the material between observer and object and its interaction processes with radiation, but second also on our visual perception system. After a rough comparison of ranges in water, glass, and the atmosphere, we focus on the physical basis of visual range for the latter. As a contrast phenomenon, visual range refers to allowed light paths within the atmosphere. It results from the interplay of geometry, refraction, and light scattering. We present a concise overview of this field by qualitative descriptions and quantitative estimates as well as classroom demonstration experiments. The starting point is the common geometrical visual ranges, followed by extensions due to refraction and limitations due to contrast, which depend on scattering and absorption processes within the atmosphere. The quantitative discussion of scattering is very helpful to easily understand the huge ranges in nature from meters in dense fog to hundreds of kilometers in clear atmospheres. Extreme visual ranges from about 300 km to above 500 km require optimal atmospheric conditions, cleverly chosen locations and times, and a sophisticated topography analysis. Even longer visual ranges are possible when looking through the vertical atmosphere. From the ISS, daytime ranges well above 1000 km are possible.}, language = {en} } @article{Vollmer2026, author = {Vollmer, Michael}, title = {How many stars appear colored to the naked eye?}, series = {Applied Optics}, volume = {65}, journal = {Applied Optics}, number = {9}, publisher = {Optica Publishing Group}, doi = {10.1364/AO.580635}, pages = {C27 -- C37}, year = {2026}, abstract = {Naked eye studies of the clear night sky reveal that a certain percentage of all observable stars can be perceived as having color. Subjective estimates differ widely, ranging from just a few to a maximum of above two hundred. Explanations are based on the emission spectra of the stars, which are modified by interstellar dust clouds, the Earth atmosphere, and mostly the inverse square law. Color changes occur not only for variation of the star's angular elevation above the horizon, but as well for decreasing nighttime sky brightness due to the transition from photopic via mesopic to scotopic vision. The maximum number of stars showing color to the naked eye depends on star illuminances on Earth and the background sky luminance. The limit of observing color is found to correspond to apparent visual magnitudes around , defining the number of colored stars. This also means that naked eye perception of stars with color is only possible for a certain star distance range, which is well below the maximum naked eye visual range of stars.}, language = {en} } @incollection{Vollmer2025, author = {Vollmer, Michael}, title = {Elektromagnetische Wellen - Grundlagen und ausgew{\"a}hlte Anwendungen}, series = {Schwingungen und Wellen in Alltagskontexten}, booktitle = {Schwingungen und Wellen in Alltagskontexten}, edition = {1}, publisher = {Springer}, doi = {10.1007/978-3-662-70949-8_3}, pages = {35 -- 48}, year = {2025}, abstract = {Schwingungen und Wellen zeigen sich in vielen Alltagsph{\"a}nomenen der Physik, d. h. in der Lebenswelt von Sch{\"u}lerinnen und Sch{\"u}lern. Dazu z{\"a}hlen in der Mechanik Beispiele wie Schaukeln, Seilwellen oder Wasserwellen am Strand, in der Akustik Schallwellen durch beliebige Ger{\"a}usche oder stehende Wellen in Musikinstrumenten und im Elektromagnetismus die allgegenw{\"a}rtigen elektromagnetischen Wellen. Letztere haben vielf{\"a}ltigste Anwendungen, z. B. Erhitzen mit Mikrowellenger{\"a}ten, Kommunizieren mit Smartphones, Daten{\"u}bertragung mit Lichtleitern oder Fotografieren mit Kameras, ganz zu schweigen von medizinischen Anwendungen der Endoskopie, des R{\"o}ntgens oder laserbasierten chirurgischen Eingriffen. Viele dieser Anwendungen haben ein enormes Motivationspotenzial in der Lehre, weshalb das Thema fest in Lehrpl{\"a}nen der Sekundarstufen verankert ist. Im Folgenden werden zun{\"a}chst allgemeine Grundlagen und Gemeinsamkeiten der Beschreibung beliebiger Wellen diskutiert, bevor das Hauptaugenmerk auf elektromagnetische Wellen und ausgew{\"a}hlte Anwendungen gelegt wird.}, language = {de} } @article{Vollmer2024, author = {Vollmer, Michael}, title = {Optical Phenomena in the Atmosphere}, series = {Encyclopedia of Atmospheric Sciences}, journal = {Encyclopedia of Atmospheric Sciences}, number = {2}, edition = {3}, publisher = {academic press}, doi = {10.1016/B978-0-323-96026-7.00177-6}, pages = {285 -- 306}, year = {2024}, abstract = {Following a brief description of the atmosphere and spectra of the Sun as dominant daytime light source, the most common optical phenomena within the troposphere are discussed, which are due to scattering of radiation with the constituents of the atmosphere. At first mirages, rainbows, coronas, iridescence, glories and halos are explained. Then light scattering phenomena which give rise to sunset colors, blue and colorful skies are presented as well as related phenomena like blue mountains, white clouds, green flashes and visual ranges. The review ends with a short survey of other less easily observable optical phenomena of the atmosphere and a very detailed bibliography.}, language = {en} } @book{Vollmer2024, author = {Vollmer, Michael}, title = {Optik und ihre Ph{\"a}nomene}, edition = {3}, publisher = {Springer}, isbn = {978-3-662-69308-7}, doi = {10.1007/978-3-662-69309-4}, publisher = {Technische Hochschule Brandenburg}, pages = {XXIII, 607}, year = {2024}, abstract = {Dieses Lehr-, Lern-, Fach- und Sachbuch pr{\"a}sentiert die Grundlagen der Optik in Theorie und ausf{\"u}hrlich beschriebenem Experiment sowie vielf{\"a}ltige faszinierende optische Ph{\"a}nomene. Ob in Vorlesungen, Seminaren, f{\"u}r Projektarbeiten, Schulunterricht oder Selbststudium - dieses Buch ist eine wertvolle Ressource f{\"u}r alle, die sich f{\"u}r Optik interessieren. Durch die große Zahl zitierter Originalarbeiten schl{\"a}gt es nicht nur die Br{\"u}cke zur Lehre sondern auch zur Forschung.}, language = {de} }