William Conrad Roentgen – The winner of the first Nobel Prize in physics and discoverer of X-rays is profiled by Helen Morgan

2023 marks the 100th anniversary of the death of German physicist Wilhelm Conrad Roentgen, who in 1895 discovered X-rays. This was a significant scientific development which would ultimately benefit a variety of fields, mostly medicine, by making the invisible visible. Roentgen was a skilful experimenter who had worked on a variety of topics before his ground-breaking discovery.

X-rays are electromagnetic energy waves that act similar to light waves although they are of a shorter wavelength and higher frequency with the capacity to pass through solid bodies. They can penetrate soft tissue like skin and muscle and are used to take photographs of the bones in medicine.

Roentgen was born in Prussia (now Germany) on the 27th March 1845 to Friedrich Conrad Roentgen, a German merchant and cloth manufacturer and his wife Charlotte Constanze Frowein. When he was three years old the family moved to Apeldoorn in the Netherlands where he attended the Institute of Martinus Herman von Doorn, a boarding school. While there he did not show any particular aptitude but did show a deep love of nature and was fond of roaming in the open countryside and the forests. This remained with him for the rest of his life.

In 1862, Roentgen attended a technical school in Utrecht but three years later was unfairly expelled after one of the staff accused him of having produced a caricature of a teacher which was in fact drawn by somebody else.
In 1865 he applied to attend Utrecht University but was rejected owing to his lack of the necessary academic qualifications. He then applied to the Federal Polytechnic University in Zurich, Switzerland where he was accepted and where he studied mechanical engineering. Following his studies, Roentgen worked at the University of Strasbourg, Giessen and Wurzburg, where he carried out his Nobel awarded research.

In 1869 Roentgen graduated with a PhD from the University of Zurich. Where he became a favourite student of Professor August Kundt. He later became Kundt’s assistant and went with him to Wuerzburg the same year. In 1876, he became a Professor of Physics in Wuerzburg but three years later he accepted the invitation to the Chair of Physics in the University of Giessen.

In 1872, Roentgen married Anna Bertha Ludwig of Zurich who he met in a café run by her father. The couple had no children but in 1887 they adopted Berta Ludwig, a relative then aged six.

Roentgen planned to emigrate to the United States where he had family but the outbreak of WW1 put an end to his plans. In 1900 he accepted the Chair of Physics in Munich University and remained there for the rest of his working life.

While working in his laboratory in Wuerzburg Germany, Roentgen observed that a nearby fluorescent screen glowed when a current was passed through a Crookes’ vacuum tube. He investigated the properties of the radiation responsible which he called X-rays because of their unknown nature. The first X-ray photograph he produced was of his wife’s hand.

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