Toepler
NAME: Toepler, August
ACHIEVEMENT(S): “Schileren” photography
NICKNAME/ALIAS: None
DATE/PLACE OF BIRTH: 1836, at Vienna, Austria
DATE/PLACE/AGE AT DEATH: 1912. Aged 76
DISCIPLINE: Physicist
FIELD: Physics
LANGUAGE: Austrian
PARENTS: ?
SIBLINGS: ?
SPOUSE: ?
CHILDREN: ?
EDUCATION: ?
MAJOR WORK: ?
LIFE AND TIMES: Toepler became the director of the Physics Institute at the University of Graz in Austria from 1868, and the following year he was joined by the physicist <worked with> Boltzmann*.
In 1870, during a series of experiments with Boltzmann, Toepler measured the threshold of audibility, but during his time at Graz he dedicated most of his energy to establishing a new building, new apparatus and much larger research funds for the institute. Later, he held the chair of general and experimental physics at Graz, but in 1876, frustrated by lack of funds, he moved to the University of Dresden in Germany.
In 1864 Toepler had developed a new method of photography technique now known as the 'schlieren' (=’smears’) technique which he developed for checking the glass in optical instruments, and which is now used for visually detecting and investigating the movement and behaviour of gas or air particles, by recording the variations of density produced in a gas under certain conditions.
In this technique, the flow of air (or another gas) can be photographed by shining, through the air, a beam of light concentrated at a focal point, with a camera or screen for observation placed behind the focus. Temperature gradients within the gas or air cause small displacements or deflections of individual light-rays within the beam, and these effects are then reproduced as variations in the intensity of the beam exiting the air, and can be displayed on a screen or photographic plate, where they appear as shadows.
Between 1873 and 1893, the Austrian physicist and philosopher <technique used by> Mach* developed Toepler's schlieren optical and photographic technique for the observation and measurement of sound waves and wave propagation, during his investigations of the principles of supersonics.
This work was then taken up by <technique used by> Karman* in the 1930s, who first used the schlieren technique to photograph aerodynamic flow patterns in wind-tunnels, and made several important aerodynamical discoveries.
The schlieren method now has a wide variety of uses, from flame and combustion studies and ballistics, to biochemical investigations using electrophoresis (the movement of electrically charged molecules in a solution in an electric field), as pioneered in the 1930s by the Swedish scientist <technique used by> Tiselius*.
ASSESSMENT: None
EXTRA CONNECTIONS: His work related to that of aerodynamicist <work related to> Prandtl*
His schlieren work may have been anticipated by <possibly anticipated by> Foucault*
ONELINER: August Toepler, inventor of schlieren photography
BIBLIOGRAPHY:
DSB, EB
Cercignani, Carlo, Ludwig Boltzmann: The Man Who Trusted Atoms, Oxford & New York: OUP, 1998