Heinrich Rubens

Last updated

Heinrich Rubens (30 March 1865, Wiesbaden, Nassau, Germany – 17 July 1922, Berlin, Germany) was a German physicist. He is known for his measurements of the energy of black-body radiation which led Max Planck to the discovery of his radiation law. This was the genesis of quantum theory.

Contents

After having attended realgymnasium Wöhlerschule in Frankfurt am Main, he started in 1884 to study electrical engineering at the technical universities in Darmstadt and Berlin. [1] The following year he switched to physics at the University of Berlin which was more to his liking. [2] After just one semester there he transferred to Strasbourg. There he benefited much from the lectures by August Kundt who in 1888 took over the vacant position of Hermann Helmholtz at the University of Berlin. Rubens followed after and got his doctors degree there the same year. In the period 1890–1896 he was employed as an assistant at the physics institute and made his habilitation in 1892. He was then a privatdozent and was allowed to teach. Already then he was praised for his experimental investigations of infrared radiation. [3]

The grave of Heinrich and Marie Rubens in Berlin. Alter St-Matthaus-Kirchhof Rubens Heinrich.jpg
The grave of Heinrich and Marie Rubens in Berlin.

Rubens got a permanent position in 1896 as docent at the Technical University of Berlin in Berlin-Charlottenburg. He could continue his experimental research at the nearby Physikalisch-Technische Reichsanstalt. It was there he in 1900 did his important measurements of black-body radiation which made him world-famous. He was promoted to professor the same year.

After Paul Drude retired in 1906 from his professorship at the University in Berlin, the position was given to Rubens. He was at the same time appointed director of the physics institute. [1] In this way he could influence and lead a large group of colleagues and students. The year after he was elected to the Prussian Academy of Sciences and became in 1908 a corresponding member Göttingen Academy of Sciences and Humanities. [1] He participated at the two first Solvay conferences after having received the Rumford Medal in 1910 "on the ground of his researches on radiation, especially of long wave length.".

Heinrich Rubens died in 1922 after a longer illness. At a memorial meeting in the science academy the following year Max Planck said about him: [4]

Without the intervention of Rubens the formulation of the radiation law and thereby the foundation of quantum theory would perhaps have arisen in quite a different manner, or perhaps not have developed in Germany at all.

He is buried at the Alter St.-Matthäus-Kirchhof in Berlin-Schöneberg with his wife Marie. She took her life in 1941 for fear of being deported and killed by the Nazis. [5] The burial place is near that of Gustav Kirchhoff, who founded spectroscopy and formulated the first laws of black-body radiation.

Scientific contributions

Participants at the first Solvay conference 1911. Rubens is the third person from left standing in the back. 1911 Solvay conference.jpg
Participants at the first Solvay conference 1911. Rubens is the third person from left standing in the back.

Already as a student was Rubens fascinated by electromagnetic radiation as theoretically described by Maxwell and experimentally demonstrated by Hertz. Through the influence of Kundt he had become interested in understanding the optical properties of different materials. In his doctoral work he showed that reflection of light increases with increasing wavelengths into the infrared region. As a related result he could present an experimental verification of Maxwell's theory for electromagnetic waves in different media. [6] This effort also turned into a demonstration of the validity of these equations for infrared radiation. Rubens succeeded in this for wavelengths up to 10 μm. [7]

Through the improvements of instruments and invention of new techniques he could measure infrared radiation for larger and larger wavelengths. One of his goals was to better understand the reflexion of radiation by metals and crystals. It was known that this became stronger for wavelengths which were absorbed. This lead him to a new, powerful method by selective reflexion from several crystals to isolate a narrow range of infrared wavelengths from a broader spectrum of radiation. Using such Reststrahlen he could in 1898 detect wavelengths of sizes around 60 μm. [4]

Together with Ferdinand Kurlbaum he started the same year to measure the energy content of black-body radiation in the far infrared region using this technique. For a fixed value of the wavelength they found that the energy increased linearly with the temperature. This was in disagreement with the ruling Wien's radiation law, but consistent with an alternative law proposed by Lord Rayleigh.

On 7 October 1900 Rubens and his wife were invited to dinner by Max Planck. Rubens told then his host about the new measurements done at a wavelength 51 μm. [8] After the guests had left Planck managed to derive a new formula for the radiation energy which was consistent with the new results. He wrote it down on a postcard which Rubens received the following day. A few days later Rubens reported back that it seemed to fit all his measurements. [9] On 14 December Planck could present to Deutsche Physikalische Gesellschaft a derivation of his new radiation law based on the idea of quantization of energy. This was the "birthday" of the new quantum physics. [10]

In the following years Rubens could improve his measurements of infrared radiation and reached wavelengths of several hundred micrometres. This enabled him also to make more and more accurate tests of Plancks new radiation theory and related studies of matter which soon could be described by quantum mechanics. [6] He was loved by his students and colleagues for his care and accuracy in all experimental work. [2] In this connection he constructed in 1905 a Rubens tube to illustrate standing sound waves using a flammable gas in a tube. This was probably inspired by his teacher Kundt's tube where fine sand or powder was used for the same purpose.

See also

Related Research Articles

Electromagnetic radiation Waves of the electromagnetic field

In physics, electromagnetic radiation (EMR) consists of waves of the electromagnetic (EM) field, propagating through space, carrying electromagnetic radiant energy. It includes radio waves, microwaves, infrared, (visible) light, ultraviolet, X-rays, and gamma rays. All of these waves form part of the electromagnetic spectrum.

The electromagnetic spectrum is the range of frequencies of electromagnetic radiation and their respective wavelengths and photon energies.

Hertz SI unit for frequency

The hertz (symbol: Hz) is the unit of frequency in the International System of Units (SI) and is defined as one cycle per second. The hertz is an SI derived unit whose expression in terms of SI base units is s−1, meaning that one hertz is the reciprocal of one second. It is named after Heinrich Rudolf Hertz (1857–1894), the first person to provide conclusive proof of the existence of electromagnetic waves. Hertz are commonly expressed in multiples: kilohertz (103 Hz, kHz), megahertz (106 Hz, MHz), gigahertz (109 Hz, GHz), terahertz (1012 Hz, THz).

Light Electromagnetic radiation that is visible to human eyes

Light or visible light is electromagnetic radiation within the portion of the electromagnetic spectrum that is perceived by the human eye. Visible light is usually defined as having wavelengths in the range of 400–700 nanometres (nm), corresponding to frequencies of 750-420 terahertz, between the infrared and the ultraviolet.

Max Planck German theoretical physicist

Max Karl Ernst Ludwig Planck was a German theoretical physicist whose discovery of energy quanta won him the Nobel Prize in Physics in 1918.

Photon Elementary particle or quantum of light

The photon is a type of elementary particle that serves as the quantum of the electromagnetic field, including electromagnetic radiation such as light and radio waves, and the force carrier for the electromagnetic force. Photons are massless, so they always move at the speed of light in vacuum, 299792458 m/s. The photon belongs to the class of bosons.

Wave–particle duality is the concept in quantum mechanics that every particle or quantum entity may be described as either a particle or a wave. It expresses the inability of the classical concepts "particle" or "wave" to fully describe the behaviour of quantum-scale objects. As Albert Einstein wrote:

It seems as though we must use sometimes the one theory and sometimes the other, while at times we may use either. We are faced with a new kind of difficulty. We have two contradictory pictures of reality; separately neither of them fully explains the phenomena of light, but together they do.

Wiens displacement law

Wien's displacement law states that the black-body radiation curve for different temperatures will peak at different wavelengths that are inversely proportional to the temperature. The shift of that peak is a direct consequence of the Planck radiation law, which describes the spectral brightness of black-body radiation as a function of wavelength at any given temperature. However, it had been discovered by Wilhelm Wien several years before Max Planck developed that more general equation, and describes the entire shift of the spectrum of black-body radiation toward shorter wavelengths as temperature increases.

Black body Idealized physical body that absorbs all incident electromagnetic radiation

A black body or blackbody is an idealized physical body that absorbs all incident electromagnetic radiation, regardless of frequency or angle of incidence. The name "black body" is given because it absorbs all colors of light. A black body also emits black-body radiation. In contrast, a white body is one with a "rough surface that reflects all incident rays completely and uniformly in all directions."

In physics, Planck's law describes the spectral density of electromagnetic radiation emitted by a black body in thermal equilibrium at a given temperature T, when there is no net flow of matter or energy between the body and its environment.

Gustav Ludwig Hertz German physicist

Gustav Ludwig Hertz was a German experimental physicist and Nobel Prize winner for his work on inelastic electron collisions in gases, and a nephew of Heinrich Rudolf Hertz.

Absorption spectroscopy Spectroscopic techniques that measure the absorption of radiation

Absorption spectroscopy refers to spectroscopic techniques that measure the absorption of radiation, as a function of frequency or wavelength, due to its interaction with a sample. The sample absorbs energy, i.e., photons, from the radiating field. The intensity of the absorption varies as a function of frequency, and this variation is the absorption spectrum. Absorption spectroscopy is performed across the electromagnetic spectrum.

Franck–Hertz experiment Experiment confirming quantisation of energy levels

The Franck–Hertz experiment was the first electrical measurement to clearly show the quantum nature of atoms, and thus "transformed our understanding of the world". It was presented on April 24, 1914, to the German Physical Society in a paper by James Franck and Gustav Hertz. Franck and Hertz had designed a vacuum tube for studying energetic electrons that flew through a thin vapor of mercury atoms. They discovered that, when an electron collided with a mercury atom, it could lose only a specific quantity of its kinetic energy before flying away. This energy loss corresponds to decelerating the electron from a speed of about 1.3 million meters per second to zero. A faster electron does not decelerate completely after a collision, but loses precisely the same amount of its kinetic energy. Slower electrons merely bounce off mercury atoms without losing any significant speed or kinetic energy.

Black-body radiation Thermal electromagnetic radiation

Black-body radiation is the thermal electromagnetic radiation within or surrounding a body in thermodynamic equilibrium with its environment, emitted by a black body. It has a specific spectrum of wavelengths, inversely related to intensity that depend only on the body's temperature, which is assumed for the sake of calculations and theory to be uniform and constant.

Max Planck Institute for Physics

The Max Planck Institute for Physics (MPP) is a physics institute in Munich, Germany that specializes in high energy physics and astroparticle physics. It is part of the Max-Planck-Gesellschaft and is also known as the Werner Heisenberg Institute, after its first director in its current location.

Quantum mechanics is the study of very small things. It explains the behavior of matter and its interactions with energy on the scale of atomic and subatomic particles. By contrast, classical physics explains matter and energy only on a scale familiar to human experience, including the behavior of astronomical bodies such as the Moon. Classical physics is still used in much of modern science and technology. However, towards the end of the 19th century, scientists discovered phenomena in both the large (macro) and the small (micro) worlds that classical physics could not explain. The desire to resolve inconsistencies between observed phenomena and classical theory led to two major revolutions in physics that created a shift in the original scientific paradigm: the theory of relativity and the development of quantum mechanics. This article describes how physicists discovered the limitations of classical physics and developed the main concepts of the quantum theory that replaced it in the early decades of the 20th century. It describes these concepts in roughly the order in which they were first discovered. For a more complete history of the subject, see History of quantum mechanics.

Erich Regener

Erich Rudolf Alexander Regener was a German physicist known primarily for the design and construction of instruments to measure cosmic ray intensity at various altitudes. He is also known for predicting a 2.8 K cosmic background radiation, for the invention of the scintillation counter which contributed to the discovery of the structure of the atom, for his calculation of the charge of an electron and for his early work on atmospheric ozone. He is also credited with the first use of rockets for scientific research.

The history of quantum mechanics is a fundamental part of the history of modern physics. Quantum mechanics' history, as it interlaces with the history of quantum chemistry, began essentially with a number of different scientific discoveries: the 1838 discovery of cathode rays by Michael Faraday; the 1859–60 winter statement of the black-body radiation problem by Gustav Kirchhoff; the 1877 suggestion by Ludwig Boltzmann that the energy states of a physical system could be discrete; the discovery of the photoelectric effect by Heinrich Hertz in 1887; and the 1900 quantum hypothesis by Max Planck that any energy-radiating atomic system can theoretically be divided into a number of discrete "energy elements" ε such that each of these energy elements is proportional to the frequency ν with which each of them individually radiate energy, as defined by the following formula:

Planck constant Physical constant in quantum mechanics

The Planck constant, or Planck's constant, is a fundamental physical constant denoted , and is of fundamental importance in quantum mechanics. A photon's energy is equal to its frequency multiplied by the Planck constant. Due to mass–energy equivalence, the Planck constant also relates mass to frequency.

Otto Wiener (physicist)

Otto Heinrich Wiener was a German physicist.

References

  1. 1 2 3 H. Kant, Heinrich Rubens, Deutsche Biographie.
  2. 1 2 W. Westphal, Heinrich Rubens, Die Naturwissenschaften 10 (48), 1017–1020 (1922).
  3. H. Rubens, Über Dispersion ultraroter Strahlen, Annalen der Physik 45, 238 (1892).
  4. 1 2 Jagdish Mehra, The Golden Age of Theoretical Physics, World Scientific, Singapore (2001). ISBN   978-9810-24342-5
  5. Stolpersteine, Marie Rubens, Berlin.
  6. 1 2 G. Hertz, Rubens und die Maxwellsche Theorie, Die Naturwissenschaften, 10 (48), 1024–1027 (1922).
  7. J.C.D. Brand, Lines of Light: The Sources of Dispersive Spectroscopy, 1800–1930, Gordon & Breach, Luxembourg (1995). ISBN   978-2884-49163-1.
  8. A. Pais, Einstein and the Quantum Theory, Review of Modern Physics, 51 (4), 863–914 (1979).
  9. G. Hettner, Die Bedeutung von Rubens Arbeiten für die Plancksche Strahlungsformel, Die Naturwisssenschaften 10 (48), 1033–1038 (1922).
  10. H. Kangro, Early History of Planck's Radiation Law, Taylor & Francis Ltd, New York (1976). ISBN   0-850-66063-7.