Greetings from KSW College of Orson Science for Women and Dr. David Kurbagaran, Assistant Professor, Department of Physics. Now we will see some important concepts of solid state physics. First we will see the definition of solid state physics. Solid state physics is a branch of physics which deals with practical and theoretical investigations of the properties of solids such as superconductivity, photoconductivity and ferromagnetism. Now let's see the objectives of solid state physics. The first one is to learn crystal structures, to study the diffraction of x-rays by crystal and defects in crystals. To know the basics of magnetism and superconductivity, to understand the electrical and dialectical properties of nonmetals, last one is to gain the knowledge of thermal and electrical properties of solids. So what is learning outcome of this paper? This course facilitates the student to understand the macroscopic properties of solids in terms of microscopic particles of the solids. Now let's see the historical background of the subject. A separate field going by the name of physics emerged in 1940s with the establishment of the division of solid state physics within the American Physical Society. Soon after war 2, large communities of solid state physics emerged in ERO, especially in England, Germany and also Soviet Union. Within the US and ERO, solid state become a prominent field through its investigation into semiconductors, superconductivity and nuclear resonance. The next one is crystal structures. A crystal structure is made up of atoms. A crystal lattice made up of points, a crystal system is a set of axes. Crystal structure is obtained by attaching atoms, groups of atoms or molecules. This structure occurs from the intrinsic nature of the constituent particles to produce symmetric pattern. A small group of repeating pattern of atomic structure is known as the unique cell of the structure. Many properties of materials are suffering from their crystal structures. This structure is often investigated employing a range of crystallographic techniques including exoract crystallography, neutron diffraction and electron diffraction. Crystal structure are derived from physical density and chemical formula of solids. There are seven crystal systems and are stated below with illustrated examples. The next side refers. There are seven crystal structures and bravis lattice lefers to 14 different three-dimensional configuration into, with atoms can be arranged in crystals. Four types of unit cells, P lefers to primitive, I lefers to body center, F lefers to face center, C lefers to side center. The letters A, B, C have been used to denote the dimension of the unit cells, whereas alpha-beta gamma denotes the corresponding angles within the unit cell. We will catch up in the next video. Thank you for watching the video.