X-rays was discovered accidentally in 1895 by William Roentgen. In principle the production of x-rats is the inverse of the photo-electric effect and can therefore be interpreted in a similar manner.
Production of x-rays; the x-rays are produced when thermally generated electrons from a hot filament are accelerate through a high voltage and focused onto a tungsten target.
The electrons are produced by thermionic emission from the hot cathode which is a heated tungsten filament. This filament lies inside a curved metal cylinder which acts to focus the emitted electrons on to a tungsten target embedded in a copper block which also acts as the anode.
Tungsten is used as the target because it n is a metal of high melting point. The metal cylinder is kept at a high negative potential relative to the anode. The serves to accelerate the electrons through the x-rays tube which is also evacuated in order that the accelerated electrons can get to their target without losing much of their energy. A large fraction of the kinetic energy of the accelerated electrons is transformed in to heat when these electrons are suddenly stopped on hitting the tungsten target. The target must therefore be made of a metal of high melting point. The rest of the energy of the electrons is converted into x-rays which are radiated from the tungsten target through a window.
The heat so generated is conducted through the copper anode of high conductivity and removed by cooling fins.
Types of x-rays;
There are two types of x-rays. They are;
- The hard x-rays which have a high penetrating power and a short wavelength.
- Soft x-rays which have a lower penetrating power and longer wavelength.
Hardness is a measure of the strength or penetrating ability of the x-rays. Intensity is the energy radiated per unit time per unit area by the x-rays. The intensity of the x-rays is governed by the current of the hot filament.
Characteristics and properties of x-rays.
- X-rays are electromagnetic waves of very high frequency.
- They are diffracted by crystals.
- They ionize gases
- They have short weave length much shorter than that of light waves.
- Their major characteristic is that they have a high penetrating power.
- They cause fluorescence in zinc substances.
- They cause the liberation of electrons when they fall on certain substances.
Practical Application of x-rays.
- Because of their high penetrating power, x-rays are used for examining the body to locate broken bones or hidden metallic objects like bullets in a patient’s leg or a pin swallowed y a child.
- They can be used to detect alterations which have been made on works of arts.
- They are used in the treatment of tumours and some skin disease. Cancer cell can destroyed by x-rays.
- They are used in airports to detect metals and contraband on a baggage.
- They are used in radio-therapy; radiography and in agricultural to kill germs.
Hazards of X-rays and safety Precautions.
Exposure to x-rays can burn the skin. Deeper within the body, the x-rays can also destroy body cells. X-rays cause genetic mutations with understandable hereditary consequences. They can damage body tissues and cause leukemia.
Special precautions are therefore necessary for people who work with x-rays. They should wear lead coats, and have regular health checks.