Roentgen (unit) absorbed dose in a wide range of matter. When measuring absorbed dose in a human due to external exposure, the SI unit the gray, or the related non-SI rad are used. From these can be developed the dose equivalents to consider biological effects from differing radiation types and target materials. These are equivalent dose, and effective dose for which the SI unit sievert or the non-SI rem are used. The following table shows radiation quantities in SI and non-SI units: Roentgen (unit) The roentgen or röntgen () (symbol R) is a legacy unit of measurement for the exposure of X-rays
Wilhelm Filehne at the medical polyclinic. In 1876 he became an associate professor of pharmacology at Erlangen, and ten years later, was appointed a full professor of the same subject at the University of Breslau. In 1911 he was succeeded at Breslau by Julius Pohl. In addition to work in the field of pharmacology, he made contributions in his research of optical illusions, being known for his experimentation with a phenomenon known as a Zöllner illusion. The so-called "Filehne illusion" is the illusory motion of a stationary background when smooth pursuit eye movements are made across the stationary background. Wilhelm Filehne Wilhelm