August 17, 2014

X-Rays- Formation, Properties & Applications Explained

In 1895, Wilhelm Roentgen discovered X-rays. This accidental discovery took place when he was studying cathode rays using an evacuated glass tube. X-Rays are electromagnetic radiations having a wavelength between 10A to 0.01A. In Free Space they travel in a straight line with a velocity of 3 ×10 (power) 8 meters per second and they are Invisible to human Eye.

Formation: When cathode rays strike against a metal of high atomic weight, a new form of radiation called X-rays, are produced. X-rays are generated when a stream of electrons travelling from tungsten filament (cathode) is suddenly stopped by its impact on anodic tungsten target .
Properties of X Rays
 (i) X-rays are electromagnetic waves and part of the electromagnetic spectrum. They are electromagnetic waves heaving extremely short wave length about a thousand times shorter than those of visible rays (1 to 3 AU).
(ii)        X-rays carry no charge on them. X-rays diverge from the source and cannot be focused to a point.
(iii)       X-rays travel along straight line like cathode rays.
(iv)       They produce fluorescence on certain substances which they strike, such as rock salt.
(v)        They can ionise gases due to high velocity and KE associated with them. They have a very short wavelength (about the same size as the diameter of an atom. They cause ionisation (adding or removing electrons in atoms and molecules)
(vi)       they can cause photoelectric emission
(vii)      They can be reflected and refracted but not through ordinary plane surface.
(viii)     They produce interference and diffraction phenomenon.
(ix)       They cannot be deflected by electric and magnetic fields.
(x)        They can produce secondary X-rays when they strike metals.
(xi)       X Electrical and magnetic fields fluctuate perpendicular to the direction of X-rays and at right angles to each other.
(xii)      They have the properties of Attenuation, Absorption & Scattering.
(xiii)     Chemical Properties:  X-Ray induces colour changes of several substances or their solutions. X-Rays bring about chemical changes in solution because X-Rays produce highly active radical OH ions in water, which react with the solutes.X-Rays cause destruction of the fermenting powers of Enzymes
(xiv)     Biological Properties: The excitation property of X-Rays are used in treatment of malignant lesions.  X-Rays also have a germicidal or bactericidal effect. Somatic Effect-This ranges from simple Sun Burn to Severe dermatitis or to change in blood supply to malignancy.
(xv)      Physiochemical Property:  X-rays are capable of producing an image on a photographic film

Applications of X Rays in Various Fields:
 (i) In medical science and in surgery for detection of:
(a)        Fractures.
(b)        Foreign matters.
(c)        Diagnosis of tumors, ulcers, tuberculosis, stones in kidneys etc.
(d)       Ionising effect of X-rays: The ionising properties of X-rays mean that they can damage the DNA in cells. The ionising effect of X-rays is more damaging to actively dividing cells in the body.
Low doses of X-rays may cause cancer - whereas high doses may kill cancerous cells.
(f)        Cancer treatment: Cancer is a disease in which cells divide uncontrollably because of changes in their DNA, forming tumours. One method of treating cancer is to direct high energy X-rays at the tumours. This causes so much damage to the cancerous cells that they die. This treatment is called radiotherapy.
(ii)        In detective department: Solid materials like gold and jewellery carried by smugglers can be detected at the check outposts. Similarly the banned materials concealed in packages can be detected by passing X-rays through them.
(iii)       In technology : Any minute crack inside the solid material can be detected.
(iv)       In industry: For examination of rubber tyres, golf balls, wireless valves, testing homogeneity of timber and uni-formality of insulating materials, detecting the presence of pearls, etc.
(v)        Digital X-rays porperties are, inspection is becoming more and more important for quality assurances in food industry .A typical application is inspection of food for foreign bodies.
(vi)       They are also used in the field of archeology for restoration of objects of historical importance.
(vii)      Hard properties of X-rays have shorter wavelength with high penetration power and are used in diagnostic radiology
(viii)     Soft X-rays have longer wavelength and less penetration power and are used in radiation therapy.

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