(N/A) Wilhelm Roentgen in $1895$ showed that when high-speed electrons strike a dense metal target in a cathode ray tube,they produce rays that cause fluorescence in materials placed outside the tube. He named them $X$-rays.
Production: $X$-rays are produced when fast-moving electrons are suddenly decelerated upon striking a dense metal anode (target).
Characteristics: $(i)$ $X$-rays are not deflected by electric or magnetic fields,indicating they are neutral.
$(ii)$ They possess very high penetrating power through matter.
$(iii)$ They have very short wavelengths,typically in the range of $\sim 0.1 \ nm$.
$(iv)$ They exhibit electromagnetic wave character.
Uses: Due to their high penetrating power,$X$-rays are extensively used in medical imaging to study the interior of the human body and in industrial applications to detect structural defects in objects.