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Collections Frits Zernike (1888-1966): Life and Work

Part 6: Zernike and the Unsung Heroes

Frits Zernike was known for his ability to resolve problems and for his craftsmanship. He made many of his test setups himself. However, due to time restrictions, he could not finish all his inventions alone. That is where the instrument makers of the institute came into the picture. They built equipment for all kinds of purposes: mechanical, electronic, with metal or as a glassblower. An assignment was never impossible.

Zernike’s regular companion was technician and instrument maker J.H. Oosterwijk. Oosterwijk is a mysterious figure, illustrated by the fact that there are hardly any photographs of him. On the photo attached to this piece he is portrayed in the back, the second man from right, almost out of sight by a lamp.

One of the most significant examples of the collaboration between Zernike and Oosterwijk is the depicted photometer. This is an instrument which measures the amount of blackening on a photographical plate, for instance when examining radiation effects. Formerly, this was done by comparing the light source of a known power. The photometer made the comparison partly automated.

The photo plate moves through a light beam using a motor with gear system. By noticing the difference in blackening, the light beam is able to go either a little or a lot through the surface. The light falls onto a photo-electric cell, which transmits it to voltage. Afterwards, this voltage is registered by an mirror galvanometer and made in to a graph on a synchronized roll of photographical paper.

Admittedly, seeing the machine is believing in this case! The many fine details and its magnificent finish are an ultimate homage to all invisible employees who work behind the scenes of the university.

Last modified:16 March 2023 3.19 p.m.
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