What did Tesla call the X-ray images he produced in 1896?

Tesla called the X-ray images he produced in 1896 “shadowgraphs.” The name described the dark outlines formed when X-rays passed through an object and exposed a photographic plate, much like a shadow recorded by invisible radiation.

Tesla began investigating unusual forms of radiant energy after noticing damage to photographic film during earlier experiments with discharge tubes. After Wilhelm Röntgen publicly announced X-rays in late 1895, Tesla quickly performed his own experiments using high-voltage equipment and vacuum tubes of his design. His images included views of feet, hands, and objects concealed by clothing or other material.

Tesla's work was part of the rapid international effort to understand Röntgen's discovery. The terms “X-ray,” “Roentgen ray,” “radiograph,” and “shadowgraph” all appeared in early discussions, which can cause confusion in modern quizzes. “Radiograph” is the later technical term for an X-ray image, while “shadowgraph” is the distinctive term associated with Tesla's early descriptions. His equipment also exposed the hazards of prolonged experimentation before radiation safety was understood.