CHAPTER NUMBER: 19 NUCLEAR PHYSICS Syeda Bint-e-Zehra Naqvi NUCLEAR PHYSICS The branch of science which deals with the study of nucleus of an atom is called Nuclear Physics. ISOTOPES Atoms of same element which have same atomic number but different mass number are called Isotopes of that element. Isotopes of an element have same chemical properties but different physical properties. Examples Hydrogen has three isotopes; Proteome, Deuterium, Tritium. RADIOACTIVITY Those elements which have atomic number greater than 82 emit certain radiation without the aid of an external source. These radiations are called Radioactive radiation, the elements are called Radioactive elements and the phenomena is called Radioactivity. HALF- LIFE Half-life of the radioactive element can be defined as: “The time required by one half of originally present atoms of a radioactive element (parent element) to this integrate into daughter element is termed as half-life of that element” 

It is represented by “T ½”

EINSTEIN MASS ENERGY RELATION In 1905 Albert Einstein proposed theory of inter convertibility of matter and energy whose mathematical expression is E=m Where E represents energy produced as a result of Mass of the matter into energy and C indicates speed of light. This equation is known as Mass Energy relation. Enormous amount of energy released during Nuclear reaction could be understood on the basis of this equation. NUCLEAR FISSION The process in which a heavy nucleus is broken into two lighter Nuclei with the production of enormous amount of energy is called Nuclear Fission.

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CHAPTER NUMBER: 19 NUCLEAR PHYSICS Syeda Bint-e-Zehra Naqvi NUCLEAR FUSSION The process in which lighter nuclei are brought together to form a heavier nucleus and they release a large amount of energy then Nuclear fission. ATOM The smallest particle of an atom which cannot be divided into any other substance is called Atom. ATOMIC NUMBER The number of proton present in nucleus is called Atomic number. 

It is represented by Z.

MASS NUMBER The sum of number of proton and neutron is called Mass number. 

It is represented by A.

PROPERTIES OF RADIOACTIVE RAYS Alpha Rays    

They have positive charge They have kinetic energy When they strike to Zinc they produce light. They are actually fast moving.

Beta Rays    

They have negative charge They have kinetic energy They produce light when they strike to Zinc. They are high power rays.

Gamma Rays    

They do not have any charge. They are electromagnetic waves. They have Kinetic energy. They produce light when they strike to Zinc.

RADIO ISOTOPES Those species of an element having isotopes and are radioactive in nature called Radio Isotopes. [email protected] edu.zikra.pk

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CHAPTER NUMBER: 19 NUCLEAR PHYSICS Syeda Bint-e-Zehra Naqvi CHAIN REACTION As discussed before, in a fission reaction each nucleus emits about two or three neutrons. These neutrons may collide with the other uranium nuclei and cause fission in them. The nuclei which undergo a fission reaction will emit neutrons. These neutrons will produce further fission in other nuclei. If this process continuous, more and more neutrons are produced and a larger amount of energy is released. This is called a nuclear chain reaction. USES OF RADIO ISOTOPES Radio isotopes are being used in following purposes:       

Radioisotopes are used to locate the faults in machines. They are used to remove leakages in pipes. They are used to improve the quality of crops. They are used to kill harmful insects. They are used to diagnose diseases. They are used to kill bacteria present in water. They are used to prevent food.

HARMFUL EFFECTS OF RADIO ACTIVITY  

It can cause bone marrow cancer Radiations falling on the nerves can cause paralysis.

SAFETY MEASURES AGAINST RADIATIONS  

Radioactive material should be handled carefully. Doctor must wear safety clothes while using radiations.

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