X-ray

X-rays (German: Röntgenstrahlen) are a form of electromagnetic radiation with a wavelength approximately in the range of 5 pm - 10 nanometers (corresponding to frequencies in the range 30 PHz - 60 EHz).

X-rays with a wavelength longer than 0.1 nm are called soft X-rays. At wavelengths shorter than this, they are called hard X-rays. Hard X-rays overlap the range of long-wavlength (low energy) gamma rays, however the distinction between the two terms refers to the source of the radiation, not its wavelength: X-ray photons are generated by energetic electron processes, gamma rays by transitions within atomic nuclei.

History

X-rays were first observed and documented in 1895 by Wilhelm Conrad R�ntgen, a German scientist who found them quite by accident when experimenting with vacuum tubes. Later, he took an X-ray photograph of his wife's hand which clearly revealed her wedding ring and her bones. On January 12, 1896 H.L. Smith[?] was the first person to take a x-ray photograph and the X-ray machine was exhibited for the first time on January 18. The photograph electrified the general public and aroused great scientific interest in the new form of radiation. R�ntgen called it "X" to indicate it was an unknown type of radiation. The name stuck, although (over R�ntgen's objections), many of his colleagues suggested calling them R�ntgen rays. They are still referred to as R�ntgen rays in some countries.

Uses

X-rays are highly penetrating of many materials, and are used in medicine to take pictures of bones and teeth. This is because bones absorb the radiation more than the less-dense soft tissue. X-rays from a source are passed through the body and onto a photographic plate; areas where radiation is absorbed show up as white and can be used to show broken or fractured bones. For imaging the digestive system, barium is swallowed.

Exposure to X-ray radiation is dangerous and cancer causing, so radiographers try to keep exposure to the patient to a minimum. Radiographers themselves wear lead aprons or stay behind a lead screen.

Diffraction of X-rays in chemistry can be used to investigate the structures of crystals and other structures - X-ray crystallography.

X-ray Astronomy is the study of the universe by analyzing the X-ray radiation which we receive on the earth.

Some lasers use on X-rays.