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- Physicist Frits Zernike, 1888
- Painter Andrea del Sarto, 1486
- Civil Rights Activist Ida Bell Wells-Barnett, 1862
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Frits Zernike (July 16, 1888 – March 10, 1966) was a Dutch physicist and winner of the Nobel prize for physics in 1953 for his invention of the phase contrast microscope, an instrument that permits the study of internal cell structure without the need to stain and thus kill the cells.
Zernike was born in Amsterdam, Netherlands, to Carl Frederick August Zernike and Antje Dieperink. Both parents were teachers of mathematics, and he especially shared his father's passion for physics. He studied chemistry (his major), mathematics and physics at the University of Amsterdam. In 1912 he was awarded a prize for his work on opalescence in gases. In 1913 he became assistant to Jacobus Cornelius Kapteyn at the astronomical laboratory of Groningen University. In 1914, he was responsible jointly with Leonard Salomon Ornstein for the derivation of the Ornstein-Zernike equation in critical-point theory. In 1915, he obtained a position in theoretical physics at the same university and in 1920 he was promoted to full professor of theoretical physics.
In 1930, Zernike was conducting research into spectral lines and discovered that the so-called ghost lines that occur to the left and right of each primary line in spectra created by means of a diffraction grating, have their phase shifted from that of the primary line by 90 degrees. It was at a Physical and Medical Congress in Wageningen in 1933 that Zernike first described his phase contrast technique in microscopy. He extended his method to test the figure of concave mirrors. His discovery lay at the base of the first phase contrast microscope, built during World War II.
Another contribution in the field of optics is related to the efficient description of the imaging defects or aberrations of optical imaging systems like microscopes and telescopes. The representation of aberrations was originally based on the theory developed by Ludwig Seidel in the middle of the nineteenth century. Seidel's representation was based on power series expansions and did not allow a clear separation between various types and orders of aberrations. Zernike's orthogonal circle polynomials provided the optics community with a crystal-clear tool to separate the various aberrations and to easily solve the long standing problem of the optimum 'balancing' of the various aberrations of an optical instrument. Since the 1960s, Zernike's circle polynomials are widely used in optical design, optical metrology and image analysis.
Zernike's work helped awaken interest in coherence theory, the study of partially coherent light sources. He died in hospital at Amersfoort, Netherlands, in 1966 after suffering illness the last years of his life.
Zernike has an Erdős number of six. The university complex to the north of the city of Groningen is named after him (Zernike park), as is the crater Zernike on the Moon. Zernike's great-nephew Gerardus 't Hooft won the Nobel Prize in physics in 1999.
