X-ray

An X-ray (or Röntgen ray) is a form of electromagnetic radiation with a wavelength in the range of 10 to 0.01 nanometers, corresponding to frequencies in the range 30 PHz to 30 EHz. They are longer than Gamma rays but shorter than UV rays. X-rays are primarily used for diagnostic radiography and crystallography. X-rays are a form of ionizing radiation and as such can be dangerous. In many languages it is called Röntgen radiation after one of the first investigators of the X-rays, Wilhelm Conrad Röntgen.

Structures that are dense (such as bone) will block most of the x-ray particles, and will appear white. Metal and contrast media (special dye used to highlight areas of the body) will also appear white. Structures containing air will be black and muscle, fat, and fluid will appear as shades of gray.