Spectrometry; structure determination of
molecules, cancer therapy, diagnostic medicine,
nondestructive testing of metals, identification of
original paintings, preservation of foods.
定義
Electromagnetic radiation of extremely short wavelength (0.06–120 A), emitted as the result of electron transitions in the inner orbits of heavy atoms bombarded by cathode rays in a vacuum tube. Those of the shortest wavelength have the highest intensity and are called “hard” X-rays. X-radiation was discovered by Roentgen in 1898. Its properties are (1) penetration of solids of moderate density, such as human tissue but retardation by bone, barium sulfate, lead, and other dense materials. (2) Action on photographic plates and fluorescent screens. (3) Ionization of the gases through which they pass. (4) Ability to damage or destroy diseased tissue; there is also a cumulative deleterious effect on healthy tissue.
危険性
Overexposure can permanently damage
cells and tissue structures; effect is cumulative.
农业用途
X-rays are electromagnetic radiation of extremely short
wavelength (0.06 to 120 A), emitted as a result of
electron transitions in the inner orbits of heavy atoms
bombarded by cathode rays in a vacuum tube. Those of
the shortest wavelength have the highest intensity and are
called 'hard' x-rays. x-radiation was discovered by
Roentgen in 1898. x-rays have the following properties:
(i) They penetrate solids of moderate density, such as
human tissue; they are retarded by bone, barium
sulphate, lead and other dense materials. (ii) They act on
photographic plates and fluorescent screens. (iii) They
ionize gases through which they pass. (iv) x-rays damage
or destroy diseased tissue. There is also a cumulative
deleterious effect on healthy tissue.
X-rays find wide use in medicine both for diagnosis
and treatment and in engineering where radiographs are used to show up minute defects in structural members. X-ray
tubes must always be carefully shielded because the
radiation causes serious damage to living tissue.
