PROJECT :- RADIOACTIVITY.: PROJECT :- RADIOACTIVITY. MADE BY :- SUNDEEP MALIK. Ⅷ A. DEFINITION OF RADIOACTIVITY :-: DEFINITION OF RADIOACTIVITY :- The phenomenon due to which certain elements spontaneously emit highly penetrating rays made of sub-atomic particles is known as radioactivity. The elements that emit radioactive rays are called radioactive elements. Examples :- uranium, thorium, radium, polonium. DISCOVERY OF RADIOACTIVITY :-: DISCOVERY OF RADIOACTIVITY :- The phenomenon of radioactivity was discovered in 1896 in Paris by Professor Henry Becquerel, when he was working on the nature of phosphorescent substances. He conducted certain investigation on uranium salt. They showed that emission of such radiations was not the property of uranium salt but of the element uranium. Later, in 1898, Madam Curie and her husband Pierre Curie found that pitchblende, an ore of uranium, was more radioactive than uranium itself. This was because the ore contained, in addition to uranium, the elements radium, thorium and polonium, all radioactive elements themselves. This gave support to the view that radioactivity was an elemental property. TYPES OF RADIOACTIVE RADIATIONS :-: TYPES OF RADIOACTIVE RADIATIONS :- Alpha ( α ) rays :- These rays consists of positively charged particles called α -particles. They are Helium nuclei each containing two protons and two neutrons, but no electrons, i.e., they have two units positive charge and four amu mass. The velocity of light. The penetrating power of α -particles is not very high. They are only slightly affected by magnetic and electrical fields. Slide 5: 2. Beta ( β ) rays :- These rays consist of one unit negative charge and have mass equivalent to the mass of an electron. The velocity of β -particles is equal to the velocity of light. They have greater penetrating power compared to the α -particles. They are strongly affected by electrical and magnetic fields. 3. Gamma (y) rays :- These are electromagnetic radiations. They have neither mass nor charge. Their velocity equals to that of light. They have very high penetrating power, i.e. they can penetrate a 30 cm thick iron plate. They are not affected by electrical or magnetic fields. TYPES OF RADIOACTIVE PHENOMENON :-: TYPES OF RADIOACTIVE PHENOMENON :- There are two types of radioactive phenomenon :- Nuclear fission :- Fission means ‘breaking up’. A nuclear reaction in which a heavy atomic nucleus breaks up into two smaller nuclei, with the release of a very large amount of energy, is called nuclear fission. Nuclear fusion :- fusion means ‘to fuse or to join together’. A nuclear reaction in which the nuclei of light atoms join up to form a heavier nucleus, causing the release of a huge amount of energy, is known as nuclear fusion. HARMFUL EFFECTS OF RADIO-ACTIVITY :-: HARMFUL EFFECTS OF RADIO-ACTIVITY :- Radioactive radiations can :- cause harmful gene mutation, i.e. abnormal change in the genes of living organisms. cause skin and other types of cancer. lead to the birth of deformed babies. Cause unimaginable destruction when the are uncontrolled. USES OF RADIOACTIVE MATERIALS :-: USES OF RADIOACTIVE MATERIALS :- Radioactive materials are used in the treatment of cancer (radiotherapy) because nuclear radiations kills cancer cells. They are used also to detect any disorder in our body system (radio tomography). Radioactive rays are used to sterilize food, drugs, etc., at normal temperature. They are used also to determine the age of rocks, fossils, mineral deposits, historical findings, etc. NUCLEAR ENERGY :-: NUCLEAR ENERGY :- The energy that is stored in the atomic nuclei of the elements is known as nuclear energy. Nuclear energy can be obtained in the form of heat and light by :- The nuclear fission of heavy elements like uranium, polonium, etc. The nuclear fusion of lighter elements like hydrogen. Nuclear Nuclear Fission. Fusion. NUCLEAR POWER PLANT :-: NUCLEAR POWER PLANT :- Nuclear power plant are set up to generate electricity. Several nuclear power plants are functioning in India. They are at Tarapur, Kalpakkam, Kota, Narora, etc. A nuclear power plant consists of :- A nuclear reactor, where nuclear fission takes place. A turbine and a generator for conversion of nuclear energy into mechanical and electrical energy respectively. A Nuclear power plant. Slide 11: THE END.