Max Karl Ludwig Planck                      (1858-1947)

    Max Karl Planck was a German physicist and Nobel laureate, who was the originator of the quantum theory. Planck was born in Kiel on April 23, 1858, and educated at the universities of Munich and Berlin. He was appointed professor of physics at the University of Kiel in 1885, and from 1889 until 1928  filled the same position at German physicist and Nobel laureate, who was the originator of the quantum theory.
    The Quantm theory is a theory based on using the concept of the quantum unit to describe the dynamic properties of subatomic particles and the interactions of matter and radiation. The foundation was laid by the German physicist Max Planck, who postulated in 1900  that energy can be emitted or absorbed by matter only in small, discrete units called quanta. Also fundamental to the development of quantum mechanics was the uncertainty principle, formulated by the German physicist Werner Heisenberg in 1927, which states that the position and momentum of a subatomic particle cannot be specified simultaneously.
      At the turn of the century, physicists did not yet clearly recognize that these and other difficulties in physics were in any way related. The first development that led to the solution of these difficulties was Planck's introduction of the concept of the quantum, as a result of physicists' studies of blackbody radiation during the closing years of the 19th century. The term blackbody refers to an ideal body or surface that absorbs all radiant energy without any reflection. A body at a moderately high temperature a "red heat" gives off most of its radiation in the low frequency red and infrared regions; a body at a higher temperature "white heat" gives off comparatively more radiation in higher frequencies yellow, green, or blue. During the 1890s physicists conducted detailed quantitative studies of these phenomena and expressed their results in a series of curves or graphs. The classical, or prequantum, theory predicted an altogether different set of curves from those actually observed. What Planck did was to devise a mathematical formula that described the curves exactly; he then deduced a physical hypothesis that could explain the formula. His hypothesis was that energy is radiated only in quanta of energy hu, where u is the frequency and h is the quantum action, now known as Planck's constant.
      Developing his quantum theory further, he discovered a universal constant of nature, which came to be known as Planck's constant. Planck's law states that the energy of each quantum is equal to the frequency of the radiation multiplied by the universal constant. His discoveries did not, however, supersede the theory that radiation from light or matter is emitted in waves. Physicists now believe that electromagnetic radiation combines the properties of both waves and particles. Planck's discoveries, which were later verified by other scientists, were the basis of an entirely new field of physics, known as quantum mechanics, and provided a foundation for research in such fields as atomic energy.
Planck received many honors for his work, notably the 1918 Nobel Prize in physics. In 1930 Planck was elected president of the Kaiser Wilhelm Society for the Advancement of Science, the leading association of German scientists, which was later renamed the Max Planck Society. He endangered himself by openly criticizing the Nazi regime that came to power in Germany in 1933 and was forced out of the society, but became president again after World War II. He died at Göttingen on October 4, 1947.
 
 

 Physics Third Edition-Douglas C. Giancoli
       pg.721,719-99
 

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