X -RAYS AND GAMMA – RAYS
The discovery of X- rays was accidentally made by a German professor Rontgen in 1895. In laboratory , X-rays can be produced by using Coolidge X-rays tube . Their frequency range is 10¹6 to 3×10¹9 Hz.
X-rays have following properties .
1. X-rays are electromagnetic waves of very short wave length ranging from 0.01Aº to 10Aº.
2. X-rays travel in vacuum with the speed of light, as they are also electromagnetic waves.
3. They are not deviated by electric and magnetic fields .
4. They affect the photographic plate very intensely.
5. They ionise the gas through which they pass.
6. They cause fluorescent in the substance like zinc , sulphide , barium , platino- cyanide, calcium tungstate, etc .
7. Like light, X-rays can also cause photoelectric effect.
8. They travel in straight line and while doing so, they cast the shadows of the objects falling in their path.
9. X-rays can undergo reflection , refraction, interference, diffraction and polarisation.
10. X-rays can penetrate the material that are opaque to visible or ultra-violet light . They can easily pass through paper paper, thin sheet of metals, wood flesh , etc , but they can not penetrate denser objects, such as bones , heavy metals, etc.
11. They have injurious effect on human bodies. Exposure of human body to X-rays causes reddening of the skin . The long exposures result into surface sores.
12. When X-rays fall on certain metals , secondary X-rays are accompanied by fast moving electrons.
X-rays have been found to be of great use in variety of fields as listed here.
X-rays are used in surgery for the detection of fractures, diseased organs , foreign matter like bullets and formation of bones or stones in the human body and observing the progress of healing bones . They are also used in diagnose the diseases.
Controlled X-rays exposure are used to cure intractable skin diseases and malignant growths. Soft X-rays are used , if the affected parts superficial, while hard X-rays are used for deep seated organs.
X-rays are used in engineering for detecting faults, cracks flaws and gas pockets in finished metal products. They are used for the testing of weldings , castings and moulds. They are also used to detect cracks in the engines of car and aeroplanes .
4. Detective department.
They are used by the detective department for detection of explosive, opium , and other contraband goods and are used by custom department for detecting gold and silver in the body of smugglers . They are also used in mints , where coins are made . They are also used for distinguishing real diamonds, gems , etc from artificial ones.
X-rays are used in industry for detecting the pearls in oysters , for testing the uniformity of insulating materials and homogeneity of timber . They are also used to examine the defect in rubber tyres , golf and tennis balls wood etc.
6. Scientific research.
X-rays have been used in investigating the structure of crystals, constitution and properties of the atoms and arrangement of atoms and molecules in the
X -RAYS AND GAMMA – RAYS (PROPERTIES AND APPLICATIONS)
GAMMA rays were discovered by Rutherford. They are emitted from the nuclei of some radioactive elements and are electromagnetic waves of very short wave length. Gamma rays can be detected with Geiger counter .
1. GAMMA rays are electromagnetic waves and have velocity equal to that of light.
2. GAMMA rays are highly penetrating . They can penetrate through several centimeters thick iron and lead blocks .
3. They have got small ionising power.
4. They can produce fluorescence in a substance like willemite.
5. They can affect a photographic plate .
6. GAMMA rays are not deflected by electric and magnetic field.
7. GAMMA rays knock out electrons from surface on which they fall .
8. GAMMA rays produce heating effects in the surface exposed to them.
1. GAMMA rays are used in radiotherapy. In hospitals, Gamma rays are used to treat cancer and tumours.
2. In food industry, soft Gamma rays are used to kill microorganisms . It helps to preserve the foodstuffs for a prolonged time.
3. GAMMA rays are used to produce nuclear reactions.