JAWAHARLAL NEHRU TECHNOLOGICAL UNIVERSITY HYDERABAD
JAWAHARLAL NEHRU TECHNOLOGICAL UNIVERSITY HYDERABAD B.Tech I Year ENGINEERING PHYSICS Previous Question Paper (October/November - 2020 - R13)
Answer any five questions. All questions carry equal marks.
Main
Obtain an expression for the packing factor of FCC structure.
Answer
In a Face-Centered Cubic (FCC) structure, the atoms touch along the face diagonal. If 'a' is the lattice constant and 'r' is the atomic radius, the face diagonal length is 4r, which equals the square root of 2 times 'a'. Thus, 4r = a√2, or a = 4r/√2 = 2r√2. The number of atoms per unit cell in FCC is 4. The volume of the atoms is 4 × (4/3)πr³, and the volume of the unit cell is a³ = (2r√2)³ = 16r³√2. The Atomic Packing Factor (APF) is the ratio of the volume of atoms to the volume of the unit cell:
List various types of bonding in solids with suitable examples.
Answer
Bonding in solids is categorized into primary and secondary types:
- Ionic bonding: Formed by electrostatic attraction between oppositely charged ions, e.g., NaCl.
- Covalent bonding: Formed by the sharing of valence electrons between atoms, e.g., Diamond (C) or Si.
- Metallic bonding: Formed by the electrostatic attraction between positive ion cores and a sea of delocalized valence electrons, e.g., Cu, Fe.
- Van der Waals bonding (Secondary): Weak dipole-dipole interactions, e.g., Solid Argon or molecular crystals.
- Hydrogen bonding (Secondary): A specific type of dipole-dipole interaction involving hydrogen atoms, e.g., Ice.
A crystal of BCC structure has atomic radius 1.2 Å. Find the volume of its unit cell.
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Explain Braggs law of X-Ray diffraction.
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Distinguish between Frenkel and Schottky defects.
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Copper has FCC structure with lattice constant 0.36nm. Calculate the interplanar spacing for (3 2 1) plane.
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Derive an expression for the de-Broglie wavelength of an electron.
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Derive time independent Schrödinger’s wave equation for a free particle.
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Calculate the de Broglie wavelength of an electron of energy 100 eV.
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Explain Bose-Einstein distribution.
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Discuss the salient features of Kronig-Penny model of a crystal.
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Explain the concept of effective mass of an electron.
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Describe different types of polarization mechanisms.
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What is meant by local field in dielectrics and how it is calculated for a cubic structure?
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Mention few applications of dielectric materials.
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How are superconductors classified based on their behavior in the magnetic field?
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Define magnetic moment. Explain the origin of magnetic moment at the atomic level.
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Explain Meissner effect.
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How do you obtain circular rings in the Newton rings experiment?
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Explain Fraunhofer diffraction due to single slit.
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Describe the construction and working of Nicol prism.
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Derive an expression for the density of holes in an intrinsic semiconductor.
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What is the Hall Effect? Obtain an expression for Hall co-efficient for n-type of semiconductor.
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Mention the factors affecting the acoustics of buildings.
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