HANDS ALL X-RAY POSITIONS

HANDS ALL X-RAY POSITIONS

HAND X-RAYS

PA HAND – This position done to visualize Fractures, dislocations of the bones, congenital deformities, or other anomalies of hand

Collimation – to include entire hand and carpals bones. For finger include distal tip of affected finer to proximal end of metacarpals bones

Centering point – entering hand at 3^rd metacarpal joint

Cassette size - - 24×30cm

Centering ray- perpendicular to the cassette

FFD- 100cm

Cassette orientation - portrait or depend on patient

Protection – gonads shielding is advisable

Position of patient – the patient should be seated at the end of the table with legs parallel to the table end and affected limb on the table and place affected hand finger palmer side down on cassette.

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OBLIQUE HAND

OBLIQUE HAND - This position done to visualize Fractures, dislocations of the bones, congenital deformities, or other anomalies of hand

Collimation – to include entire hand and carpals bones. For finger include distal tip of affected finer to proximal end of metacarpals bones

Centering point – entering hand at 3^rd metacarpal joint

Centering ray- perpendicular to the cassette

Cassette size - - 24×30cm

FFD- 100cm

Cassette orientation - portrait or depend on patient

Protection – gonads shielding is advisable

Position of patient - the patient should be seated at the end of the table with legs parallel to the table end and affected limb on the table and place affected hand/ginger Palmer side on a 45° sponge/angle thumb side raised slightly.

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LAETRAL HAND

LATERAL HAND - This position done to visualize Fractures, dislocations of the bones, congenital deformities, or other anomalies of hand

Collimation – to include entire hand and carpals bones. For finger include distal tip of affected finer to proximal end of metacarpals bones

Centering point – To enter  hand metacarpal joint

Centering ray- perpendicular to the cassette

FFD- 100cm

Cassette size - - 24×30cm

Cassette orientation - portrait or depend on patient

Protection – gonads shielding is advisable

Position of patient - the patient should be seated at the end of the table with legs parallel to the table end and place affected hand with thumb raised, down on cassette. To properly visualize the phalanges the fingers should be positioned in fan like arrangement as per pic above. This is not require if the area of the interest is the metacarpal bones.

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PA THUMB

PA THUMB - This position done to visualize Fractures, dislocations of the bones, congenital deformities, or other anomalies of thumb

Collimation – to include distal thumb and distal carpal bones

Centering point –metacarpal

Centering ray- perpendicular to the cassette

FFD- 100cm

Cassette orientation – all three thumb images can fit on one film and pa image should be to the medial side of the film

Protection – gonads shielding is advisable

Cassette size - - 24×30cm

Position of patient - the patient should be seated at the end of the table with legs parallel to the table end and place affected limb on the  table and place hand in lateral position with little finger on cassette and laying thumb so that it is parallel with the cassette. A sponge can be used to steady the thumb if required.

AMMETER AND VOLTMETER

AMMETER AND VOLTMETER

AMMETER:- An ammeter is an instrument foe measuring the currents and it is calibrated to read the values of current directly.the ammeter is always connected in series in the circuit in which current is to be measured. since it is an instrument of very low Resistance,it does not alter the value of the current in the circuit.a moving coil galvanometer can easily be change into the ammeter by placing a low resistance shunt in parallel with galvanometer.

VOLTMETER:- The voltmeter is an instrument to measure potential difference between two points and it is always connected across the two points,parallel to main current.in order that the voltmeter does not draw any appreciable current from the main current , the voltmeter should be an instrument of very high resistance. a moving coil galvanometer is converted into voltmeter by connecting a high resistance in series with galvanometer of resistance G

MAGNETIC AND ITS PROPERTIES

MAGNETIC AND ITS PROPERTIES

Just as an electric field is set up around a charged body, a magnetic field is set up around a magnet. If one pole of a magnet is moved closer to another magnet, the other magnet experiences an Attractive or Repulsive Force according to Coulomb’s law. so “The space situated around a magnet during a magnet have facing or experiences attractive or repulsive force is known as magnetic field. and a substance which itself in the north-south direction,when it is freely suspended is called ,magnet.A magnet possess a property called magnetism by which it attracts iron filings this magnetic property is due to the motion of charged particles.

i. It attracts magnetic materials towards itself.

ii. When hanging freely, the magnet always stays in the north-south direction.

iii. A point is found near each end inside the magnet where the magnetization is highest; This is called a magnetic pole.

iv. The two poles of the magnet are North Pole and South Pole.

v. Homogeneous poles have repulsion and heterogeneous poles have attraction.

vi. Magnetism can be lost when a magnet is heated, beaten or rubbed. And The ability to store energy is greater in the magnetic field than in the electric field.

LINE FOCUS PRINCIPLE

LINE FOCUS PRINCIPLE

The region present at the tungsten anode in the x-ray tube where the electron stream (stream) emitted from the cathode is called the focal spot. 99% of these incident electrons are converted into heat, only less than 1% is converted into the required x-ray. This emitted energy fails uniformly in the focal spot area.
Therefore, the larger the focal spot area, the higher the heat generated by the collision of the electron anode, the less hot the target (anode) will be, so it is less likely to melt, the smaller the focal spot, the smaller the energy of the focal spot. Causes it to melt. Therefore, to increase the heat loading capacity of the anode, it is necessary that the focal spot be taken as large as possible.

If the focal spot is enlarged, the radio graphic details are affected. The smaller the focal spot, the better the radio graphic detail on X-ray film. Therefore, to increase the lifespan of the x-ray tube it is necessary that the focal spots are enlarged and to get an X-ray of good radio graphic details, it is necessary that the focal spots should be taken as small as possible.  In 1918, the Line Focus Principle was presented, which solved all these problems.

The size and shape of the focal spot depends on the size and shape of the electron beam emitted from the anode, and the shape and size of the electron beam depends on the dimensions of the tungsten filament, the formation of the focusing cup, and the position in the focusing cup of the filament.The target surface on which the electron beam collides and tilts slightly from the vertical plane of the electron beam, this inclination from the vertical plane of the electron beam of the anode is called anode angle. The anode angle is different for an x-ray tube of different design, and in a diagnostic radiology x-ray tube it is usually about 6⁰ to 20⁰.

X-RAY TUBE DESIGN

X-RAY TUBE DESIGN

In an X-ray tube, the anode and cathode are closed in an air tight envelope, and the envelope and its inner part are called tube inserts. In most X-ray tubes, this envelope is called Pyrex Glass. ), But in some modern X-ray tubes, it is also made of metal or ceramic.     
 Functions of X-ray tube      

(i)                  It provides insulation and support to the anode and cathode.       

(ii)                It maintains vacuum in the x-ray tube.

CATHODE- the cathode is made up of tungsten wire in the form of helical filament, surrounded by a focusing cup. The filament circuit supplies a potential difference of 10v and a selectable filament current of 3-6 amperes. Electrical resistance to electron flow heats the filament to very high temperatures releasing surface electron through thermionic emission process. The rate of emission depends on the temperature. a trace of thorium in the filament not only increase the efficiency but also prolong the filament life.

the focusing cup controls the width of electron distribution and directs the electron towards the target. Usually the focusing cup is at the same potential (non biased) as the filament. In some tubes the cup is kept at more negative voltage (biased) then the filament. The later will facilitate to have a lesser focal spot size

TARGET – the anode is the target electrode, which is maintained at a positive potential. the target material should posses the following properties

·         It should have a high melting point for with standing with high temperature.

·         It should posses a high atomic number to increase the x-ray production efficiency.

·         It should posses a high thermal conductivity to dissipate heat quickly.

·         It should have a lower vapor pressure at high temperature to prevent the evaporation of target material.

Tungsten (W) is the metal widely used as the target because of its high melting point, 3770c and high atomic no 74. However, its thermal conductivity is low as 0.3. Hence a layer of tungsten is embedded over a thick block of copper. Since the thermal conductivity of copper is 0.9 the heat will be removed very quickly to the surrounding. The anode has a tendency to crack under severe stress caused by heating .therefore, tungsten-rhenium alloy 90% tungsten +10%rhenium is always used, which makes the target tougher and less likely to crack.

Molybdenum (mo ,z=42) and rhodium (rh,z+45) are commonly used as anode materials for a mammography x-ray tubes. These targets are capable of giving characteristic x-ray, suitable for soft tissue contrast studies

FOCAL SPOT SIZE - the area of the target with which the electrons are absorbed and x-rays are generated is called focal spot or focal area. if the focal area is very small .penumbra will be minimum and the picture sharpness will be good but heat removal is difficult. On the other hand, if the focal area is large, heat will be removed quickly and the picture sharpness will be reduced. This can be compromised by carful design of tube.

Usually focal spot is defined in two ways. The real focal spot size is the place on the anode that is hit by electrons. The effective focal spot size is the length and width of the emitted x-ray beam as projected down the central axis of the x-ray tube. The effective foal spot length is always smaller than the actual focal spot

TUBE COOLING - in the x-ray tube only less than 1 percent of electrical power supplied is converted into x-rays .the remaining electrical power (over 99%) is converted into heat. this large amount of heat may melt the target and therefore heat should be removed quickly from the target. Hence efficient cooling system is requiring form the x-ray tube the different method of cooling are:

·         target are made by inserting a layer of tungsten in copper block which remove the heat from the tungsten very quickly

·         X-ray tubes usually enclosed in metal case which are filled with oil for insulation purpose. this oil surround the glass envelope as well as copper block (static oil cooling).the oil convection transfer the heat from the copper block into metal case. air convection removes the heat from the metal case

·         In some modern tubes the anode is earthed and water is allowed to circulate through the anode. Sometimes the water is additionally cooled by feron gas.

HYSTERESIS LOOP

HYSTERESIS LOOP

The transfer core is made of laminated iron, which is a magnetic material. The power applied to the primary coil of an ideal transformer is fully attained on the secondary coil. However, practically no transformer is found to have 100% efficiency, that is, all the power on the primary coil should be found at secondary. This energy loss occurs in many forms. Such as the formation of Eddy current, copper losses, flux leakage and hysteresis loss etc.

If AC current is charged on the primary of the transformer, then the core made of the magnetic material of the transformer in a cycle is magnetized twice. As the direction of AC current changes, the direction of this magnetic field also changes. During this direction change, some energy is lost due to molicular friction in the core atom, this is called hysteresis loss. This can be done by choosing a suitable metal such as Mu-metal. | This metal is made of a ferromagnetic alloy consisting of 78% Nickle, 17% Iron and 5% Copper. Its permeability is very high.

STORAGE OF UNEXPOSED FILM

STORAGE OF UNEXPOSED FILM

Film is sensitive to emulsions, heat, humidity and some chemicals. Therefore some special precautions are taken for the storage of unexposed x-ray film. X-ray film storage should be in a metal box or cupboard shelves two feet above the ground or in a double wall cabinet with air flowing through the outer wall. The x-ray film is kept at a temperature of  55 ° F, relative humidity below 60 percent.

X-ray films are sensitive to gases (e.g. formaldehyde, hydrogen sulfide, sulfur dioxide, ammonia, illuminating gas, engine exhaust) and vapors (from solvents, mothballs, cleaners, turpentine, mildew and fungus preventives, and mercury) etc. This changes the sensitivity of the emulsion. So X-ray films should be kept away from them. If the film is stored for more than 6 months, it can be freeze (-18 ° C to -23 ° C) but it is slowly brought to normal temperature before being used. This prevents the emulsion layers from rolling.

X-ray film is sensitive to cosmic radiation , this cosmic radiation is found everywhere. This cosmic radiation produces fog on the x-ray film. Film fog can occur due to many reasons including scatter radiation, exposure of radiographs to light and exposure of film to radiation before exposure. Hence X-ray film is kept away from this natural background radiation.

The room where X-ray film storage is there should be away from the radiography room.

Film is also sensitive to emulsion pressure, so for film storage, the X-ray film compartments should not be stacked one on top, but should be kept standing like a book in a book.

SELF INDUCTION AND MUTUAL INDUCTION

SELF INDUCTION

If a current is to flow in a coil or circuit, a magnetic flux relationship occurs in that coil due to the magnetic field being generated. This value of the magnetic flux is proportional to the value of the flowing current.

If the current flowing is changed, the magnetic field produced by it and the corresponding magnetic flux changes, causing an induced electrical carrying force in the coil.

Thus the phenomenon of automatic induced electric force in this circuit due to change in current flowing in a coil is called self induction.

When current I flow in a circuit, the value of magnetic flux associated with the circuit is proportional to Φ current flowing.

∝ ∝ I

Φ = LI

L = best inductive coefficient or auto regulation.

Unit - Henry (H)

MUTUAL INDUCTION

When  the value of a current flowing in a coil changes, the induced current carrying force in the adjacent coil is called the reciprocal induction or Mutual induction due to the change in magnetic flux corresponding to the adjacent coil.

Mutual inductance

When I1 current flows in a primary coil or circuit, the value of the total magnetic flux in the second coil is proportional to the current flowing in the primary coil.

Φ2 ∝ I1

=2 = MI1

Here M is a constant called reciprocal inductance. Its unit is - Henry (H).

If I2 = 1A

  So M = Φ2.

The numerical value of M is the relation of the secondary coil to the value of the magnetic flux that occurs when a current flows in the primary coil.

The reciprocal induction coefficient depends on the following work-

1. On the geometry of the coils

2. Through the core placed inside the coil

3. At the distance between the coils

4. On the orientation of both coils

ALTERNATIVE CURRENT AND DIRECT CURRENT

DIRECT CURRENT(DC)
current can be classified into direct current and alternating current

The flow of electric charge in one direction is called direct current or DC current. Direct current is generated from batteries, power supply, thermocouple, solar cell and dynamo etc.In the cells or batteries chemical energy is converted into electrical energy,however  the production of large quantity of direct current is costly

Direct current flows through conductor, such as copper wire, and may also flow through semiconductor, insulator and vacuum. In it, electric current flows in a fixed direction, which separates it from AC. Earlier DC was also called Galvanic current. DC can also be obtained from AC supply with the help of rectifier. DC is also used to charge the battery.Very large amounts of DC power are used in aluminum production and other electro chemical processes. High voltage DC is used to transmit power to remote area

ALTERNATIVE CURRENT(AC)
Alternate current leads to a periodically directional change in the flow of charge. Simple AC is used for power delivery in industries, houses and office buildings.

AC is produced with the help of an alternator or in other word we can say that the machine which is used to produce alternating current is called generator or alternator It is designed for alternating current production.The current produced can be in sine, square and triangle waveform. But the sine waveform is preferred, because the sine waveform is easier to generate, and it also makes the mathematical calculations easier.

Applications of AC

AC is used in home and office outlets.

AC production and long distance transmission are easy.

There is very little energy loss in electric power transmission at high voltage for long distances. Such a transformer can be converted from high voltage to low voltage and low voltage to high voltage.

BREMSSTRAHLUNG

BREMSSTRAHLUNG

Bremsstrahlung / Continuous x-ray - the bremsstrahlung process is the result of radiative collision between the electron and a nucleus in the target or in other word we can say that It is occurs when a fast moving electron interacts with the nucleus. Electrons are negatively charged and as they pass near the positively charged nucleus, the electrons decelerates due to the attraction force, and emits their energy in the form of X-ray photons, called Bremsstrahlung x-rays or Continuous Radiation . The energy of the emitted X-ray Photon depends on how close the electrons pass through the nucleus. When electrons pass from far away, then low energy is emitted due to weakening of Coulomb force. This phenomenon is more likely to happen.

When electrons pass more close to the nucleus, the electrons are more dim, more kinetic energy is lost which comes out as high energy Xray Photon. But the probability of occurrence of this phenomenon is less.Therefore, Bremsstrahlung can contain any electron from zero to maximum energy. The maximum energy of the Bremsstrahlung Photon is determined by the maximum kinetic energy of the incident electron. And the direction of the emitted Bremsstrahlung Photon also depends on the energy of the incident photon. Electrons of less than 100 keV energy emit Xray Photon uniformly in all directions. As the energy of electrons increases, the direction of Xray Photon gets forwarded.

This is of special importance in Diagnostic Radiology in which the target is taken so thick that it stops the entire electron beam and absorbs the radiation going in the forward direction. Which gives useful Xray beam at 90 °of target.

TLD BADGE

TLD BADGE

The full form of TLD badge is thermo luminescent dosimeter and it is used as Personnel Monitoring Device. It measures X, 𝜷, 𝛄 radiation dose of an individual.Generally TLD Badge consists of a plastic cassette with a nickel coated aluminum card. This card has three CaSO4: Dy-Teflon disks 0.8 mm thick and 13.2 mm diameter.

These discs are mechanically clipped on three 12mm diameter circular holes on the card. The dimensions of the Al card are 52.5 mm X29.9 mm X 1 mm. There is a V shaped cut on the top end of the card so that these cards are always in a fixed orientation in the cassette.

 The paper of the card remains locked in the wrapper, on which the user's personal data and the period to use it are written. The thickness of the wrapper is 12mg / cm2, which denotes the 10mm depth below the skin surface. TLD disks are sealed in a thin polythene pouch with wrappers to avoid damage during incorrect use. Pouch cards protect against radioactive contamination when working with open radioactive sources.

 TLD cassettes are made of high impact plastic. It consists of three filters which are placed in front of each disk. Whose names are Cu + Al, Perspex and open respectively. These filters are mounted on the cassette both front and back of the card. The Cu + Al filter contains 1mm Al and 0.9 Cu. Cu filters are towards TLD disks and Al filters are towards radiation source. The second disc is sandwiched between 1.5mm thick plastic filters. Its density is 180mg / cm2. The third disc is placed between two circular open windows. The TLD discs are radiation recording device which are sensitive to X-rays, 𝛄 –rays, 𝜷-rays there is a clip on the cassette which attaches it to the user's clothes.

Metallic filters are used to measure X-rays and gamma rays. Perspex is for measuring beta radiation. When TLD disks are exposed, the electrons of the crystal lattice get excited and move from the valance band to the conduction band. Where they are trapped under the conduction band. The number of trapped electrons is proportional to the number of incident X-ray photons. In this way these electrons store the absorbed energy in the crystal lattice.

The TLD card used in the range of 10mr to 10,000mr.TLD badge service is conducted on quartly basis and they are sent to BARC (Bhabha Atomic Research Centre) for dose evaluation

Advantage of TLD badge:-

• Fast reading capabilities for emergency situation
• Serve as dosimeter system for monitoring patient exposure and making other exposure measurements

HIGH TENSION CABLE

HIGH TENSION CABLE

The high tension generator and X-ray tube are two different assembly and are connected by a shock proof HT cable. HT cable has three conductor wires, two for cathode and filament and one for anode. In HT Cable, these three conductor wires are arranged parallel to each other. These wires are made of copper metal and the insulator is insulated.

A flexible rubber insulation sheath is fitted around these three wires. The thickness of this rubber sheath is also increased as the voltage through the cable increases.

There is a flexible metallic sheath around this rubber sheath. This metal plate is called Woven mesh sheath. This metal sheet is connected to the earth. This metal sheet has a cover made of cotton or plastic on the outside. It provides appearances and mechanical protection to HT cable. One side of this metal sheet is attached to the X-ray tube head and the other side is connected to the transformer tank. Its connections are plug and socket type. If electrical or mechanical failure of this cable occurs, then a smell like burning occurs.

INTRODUCTION TO RADIATION

RADIATION
Radiations are the emission of electromagnetic wave or subatomic particle in the form of energy. It can be divided into two parts, ionic and non-ionic. Ionic radiation is that which reacts with matter and produces ions. Radiation can be natural and man made. The source of natural radiation is found in outer space and naturally in the core of air, water, food,Earth,sun and various natural occurring isotopes such as uranium-238 ,potassium-40 are The known radioactive substances. and the source of man made radiation are medical x-rays machines,television,tobacco,smoke detector,nuclear medicine etc

EXAMPLE OF RADIATION - The burning of candle and the sun both are emits a radiation in the form of light and heat.   

CONDUCTOR,INSULATOR AND SEMICONDUCTOR

CONDUCTOR:-Electrical conductors are materials through which electrical current flows smoothly. Copper (Cu), aluminum (Al), zinc, gold (Ag) and silver (Ag) are the electrical conductors. A large amount of free electrons are found in the electrical conductive material. Each device powered by electrical energy is manufactured by conductive material. The resistivity of a conductor or metal is 10^–6..ohm-cm.the weak bond electrons behave like free electrons and these free electrons can move freely inside the substance but cannot leave the substance. these electrons responsible for electrical conduction.all the metals are conductors. Silver is very good conductor of electricity. cu,Al,coal,mercury,human body are also conductors of electricity.

INSULATOR:-The substance in which no of free electrons are negligible or the substance in which the current does not flow easily are call insulator or nonconductor.Electrons are very strongly bound in the atom of the conductive material, so they cannot move from one place to another. In this situation, no current can go through the substance.the resistivity of the insulator is 10¹³.the examples of the insulator are wood,wax,ebonite,sulfur etc.

SEMICONDUCTOR:-A semiconductor is a substance whose electrical properties lie between conductors and conductors. Germanium and silicon are the most popular examples of these substances. According to the energy band assumption, semiconductor materials at room temperature are those that:-the conduction and connective bands are partially filled and Those between which the Forbidden energy band is quite narrow is about one electron volt, for example, it is 0.75 electron volts for germanium and about 1.12 electron volts for silicon. There are two types of semiconductors 

1) Intrinsic semiconductor:-A semiconductor in its purest form is called an intrinsic semiconductor or we can say that semiconductor in which no impurities are found is called a intrinsic semiconductor. Thus pure germanium and silicon are natural semiconductors in their natural state.

2) Extrinsic semiconductor:-An extrinsic semiconductor is formed by adding a specific type of impurities to the intrinsic semiconductor. The method of adding impurities in a semiconductor is known as doping                                                                                                                                                                                                

ATOMIC STRUCTURE,ATOMIC NUMBER,MASS NUMBER ETC

ATOMIC STRUCTURE - all the matter is composed of atoms. the atoms i very small and its diameter is of   1 × 10⁻¹⁰ meter. every atoms possesses a central core called nucleus, which is positive charged the diameter of the nucleus is of the order of  10⁻¹⁴ .the nucleus consists of two important particles called protons and neutrons.the protons are positive charged and neutron has no charged. the space around the nucleus consist of another important particles called electron. the electron are negatively charged particles and they revolve round the nucleus in elliptical orbit. no of electrons in an atom is equal to no of protons.

ATOMIC MODEL - To explain the nature of atom, many models have been proposed. they are Thomson model,niels-bohr model and sommer field model.

THOMSON MODEL - Now the problem was to understand the structure of the atom with these particles. Sir Thomson was the first to attempt to explain it. He said that the atom is like a round Christmas cake, in which the cake is made of positive charge (protons) and there is Meva Negative charge (Electron). We can also think of it as a watermelon in which the red part is positive and the seeds are negatively charged. The amount of positive and negative charge is the same, making the atom neutral. The weight of an atom is normally distributed throughout the circle.

RUTHERFORD MODEL - On the basis of this experiment, a scientist named "Rutherford" conducted another experiment, so that he could know the location of Electron. He took gold foil because he wanted a very thin layer. Then they rapidly fired alpha particles (helium atoms with no electron) on it. The alpha particle weighed 4u, so it had a lot of energy. He expected that according to the Thomson model, almost all the alpha particles would return to collide with the protons. But the results were shocking.

Almost all the alpha particles went through the gold foil.

A few particles bent slightly.

Only one particle returned 180 out of an estimated 12000.

BOHR MODEL - neil bohr suggested that the electrons are negatively charged particles and move around the nucleus in various orbits.the orbits of electron is fixed. he gave name energy levels to these orbits.the electron cannot emit any energy when it moves in its own fixed orbits known as stationary energy levels.

SOMMERFIELD MODEL - sommerfield postulate that some of the electron orbits are spherical while some other orbits are elliptical in shape. later it was proposed that each energy level have sub energy levels called sub shells,namely,p,d and f in the order of increasing energy.for particular value of n,there are equal no of possible sub-shells,out of which one is spherical and the remaining are elliptical in shape.the sub-shells are designated by the letter l known as orbital or azimuthal quantum numbers. for a particular value of n,the different value of l are 0,1,2,3........(n-1).

ATOMIC NUMBER - the atomic no of an atom is the no of protons in the nucleus which is equal to the no of electrons of the atom.it is denote by Z.

MASS NUMBER - The mass no of the atom is the total numbers of the protons and neutrons in the nucleus.it is denote by A.the mass no also refers to the atomic weight of the element and mass no of element always a whole number where atomic weight may be whole number or fraction.

ISOTOPES- the atoms composed of nuclei with same number of protons but different number of neutrons are called isotopes.in other words,isotopes have the same atomic number and different mass numbers.

ISOBARS - ISOBARS are the atoms of different elements which have same mass number but different atomic number.

TEMPERATURE AND HEAT

TEMPERATURE - matter is  made up of atoms and molecules. these atoms and molecules are in regular movement in solids and random movement in liquids an gases. hence they posses kinetic energy.  which is responsible for hotness and coldness of the body. temperature is the measure of the hotness and coldness of the body when the body is heated its molecules are in vigorous movement  therefore have a high energy and the body is said to be in high temperature.when abodyis cooled lower and lower,its kinetic energy decrease and body is said to be in lower temperature. temperature is measure in degrees with help of thermometers.there two scales of temperature namely centigrade scale and absolute scale.

Centigrade Scale In the centigrade scale of temperature, the temperature of the melting point of ice is taken as 0°C and temperature of the boiling point of water is taken as 100°C. The interval between the two is divided into 100 degrees. The scale is also called as Celsius scale.

Absolute scale In the absolute scale of temperature 0 degree is named as absolute zero and it is denoted as OK. The absolute zero is the temperature at which the molecules will have zero speed. The O K temperature is equal to -273°C in centigrade scale. The temperature of melting ice is taken as 273 K and the temperature of boiling water is taken as 373 K. The interval between the two is divided into 100 degrees. One degree interval is the same in both centigrade and absolute scale of temperature. The absolute scale is also known as Kelvin scale of temperature. In the SI system of units, the absolute scale is used. .

HEAT - heat is form of energy which can be transferred from one place to another. if a hot body and cold body are place in close contact , the hot body will transfer some of its heat until the temperature of two remain equal. there are three method of heat transfer. they are conduction, convection and radiation. conduction is the process in which heat energy is transferred without the visible motion of the particles of the heated body, conduction is take place in solid , liquid and gases. metals in general are good conductors of heat ,e.g silver,copper,etc. nonmetals are bed conductor of heat e.g glass rubber,wood,etc.convection is the process in which heat energy is transfers by the actual motion of the particles of the body. convection takes place in liquid and gases e.g trade winds, land and sea breezes. radiation is the process by which heat energy is transfers from one place to another without the aid of any material medium e.g heat reaches from the sun the si unit of the heat is joule  

FORCE,WORK,ENERGY,POWER, ETC

• FORCE - force is the influence that changes or tend to change the state of rest or of uniform motion of the body along a straight line . if the force  f acts on a body of  mass m and produces an acceleration of a then f = m*a. hence force acting on the body is equal to the product of mass of body and acceleration produced by the force on the body the si unit of force is newton and is denoted by letter "n"
• WORK -  if force acts on a body and points of application of the force is move, then work is said to be done by the force. if the force f moves a body through a distance s in its direction then work done by force is given by w=f*s.the si unit of force is joule and is denoted by letter j
• POWER - the rate of doing work is called power. its measure by the amount of work done in unit time.if W is the work done in time T then power P= w/t
• ENERGY - the energy of a body is its ability to do work. its measure by amount of work done that it can perform. the si unit of energy is joule . there are many forms of energy such as light energy , electrical energy etc
• SCALAR AND VECTOR QUANTITIES - all the physical quantities can be classified into two categories namely,scalar and vector quantities.the quantities that have only magnitude but no direction are called scalar quantities example are length,mass,time,etc and quantities that have only magnitude and as well as direction are called vector quantities example are displacement,velocity,force,etc

       

XRAYS AND ITS PROPERTIES

XRAYS AND ITS PROPERTIES

· Radiography is an imaging technique using X-rays, gamma rays, or similar ionizing radiation and non-ionizing radiation to view the internal part of the body such as  hard bones,short bones etc. X-ray were discovered by wc roengten  the German physicist in 1895  when he was investigating the conduction of electricity through the gases at low pressure in glass tube.he noticed that the positive electrodes in the tubes gives off invisible rays that cause the fluorescent screen(barium platino cyanide screen kept near the tube) to glow and fogged the photographic plates.the rays were very penetrating,they pass through black paper and even thicker objects.                                                                                          

· The properties of the x-rays are the following:-

 a)the x-rays are electromagnetic rays of shorter wavelength which behave as waves as well as particles     

 b)they have great penetrating power

 c)they travel in straight line with velocity equal to light 

 d)xray affect the photographic film and form the latent image

 e)they liberate minute amounts of heat on passing through matter
 f)they produce other chemicals as well as biological changes mainly by ionization and excitation