X-rays were first detected in the year of 1895 by the German physicist, William Conrad Roentgen. The discovery occurred during a systematic search for radiation capable of penetrating materials opaque to ordinary light.
Pinney, L. E.
"Fundamentals of X-Ray,"
Iowa State University Veterinarian: Vol. 1
, Article 8.
Available at: https://lib.dr.iastate.edu/iowastate_veterinarian/vol1/iss1/8