Unitwise Descriptive Questions

Descriptive Questions Subject : Physics code : PH1X01
Unit I
Derive expressions for growth and decay of energy density inside a hall and hence deduce Sabine’s formula for the reverberation time of the hall.
i)Explain the various factors affecting the architectural acoustics of a building and
their remedy?
ii)The average reverberation time of a hall is 1.5 secs and the area of the interior
surface is 3340 m2. If the volume of the hall is 1200 m3, find the absorption
coefficient.
i) Draw the circuit diagram of magnetostriction oscillator and explain the
construction, working and production of ultrasonic waves using it
ii) Calculate the fundamental frequency of a quarts crystal of thickness 1mm .
Gvn. Young’s modulus for quartz = 7.9 x 1010 Nm-2 and density 2650 kgm-1.
i) With a neat sketch explain the production of ultrasonic waves in piezoelectric
oscillator.
ii) Explain the application of Ultrasonics in SONAR.
i) Describe the structure of HCP crystal
ii) Calculate the axial ratio and atomic packing factor for HCP structure.
i) find the number of atoms, atomic radius, coordination number and packing density for BCC, FCC unit cells.
ii)Show that for a cubic structure the interplanar distance’d’ in terms of miller indicates and the cell edge “a” is given by .
Unit-II
Discuss in detail how plane, elliptically and circularly polarized light can be produced and analysed.
Describe the construction and working of Michelson’s interferometer. Also explain, with necessary theory a laboratory experiment of finding the wavelength of a monochromatic source of light using Michelson’s interferometer.
i)State Stress optic law.
ii)What are isoclinic and isochromatic fringes? Explain the analysis of a stressed
model in a plane polariscope?
i) Give the block diagram of a photoelastic bench and describe its components.
ii)Explain how a hologram is reconstructed.
iii)Distinguish between step index and graded index fibres.
i) With a neat diagram, explain the construction and working of C02 laser.
ii)Mention any four advantages of fibre optic sensors.
i) Explain the construction and working of Nd: YAG laser with a neat diagram.
ii)A step index fibre has numerical aperture of 0.26, core refractive index of 1.5 and a core diameter of 100 . Calculate the refractive index of the cladding.
13.i) Describe the construction and working of semiconductor laser.
ii)Explain active and passive sensors with examples
Unit III
i) What is Compton effect
ii) give the theory of Compton effect and show that the Compton shift

15.i) Derive time dependent Schroedinger wave equation and hence deduce the time
independent schroedinger wave equation.
ii) Solve Schroedinger wave equation for a particle in a one dimensional box and
obtain the energy Eigen values.
Describe the energy band theory of solids with the help of neat band diagrams. Distinguish between metals, insulators, and semiconductors on the basis of band theory.
Based on Drude Lorentz theory derive the expression for electrical conductivity and assuming the classical expression for thermal conductivity derive Wiedemann-franz law.
i) What are bound and free electrons.
ii) Derive the expression for density of states in a metal and obtain Fermi energy at 0K.
Unit IV
Derive the expressions for carrier concentrations of intrinsic semiconductors and explain the experimental method of determining the band gap of a semiconductor.
i) Distinguish between type I and type II superconductors.
ii) Describe high temperature superconductors.
i) Discuss the theory of Hall effect and derive an expression for the Hall coefficient of a material.
ii) hall coefficient of a semiconductor is 8 x 10-5m3/C and its conductivity is 250/m-ohm. Obtain the nature and concentration of charge carriers and also the mobility of the material
21.i) Derive an expression for density of holes in the valence band and also explain
how does the Fermi level vary with temperature and carrier concentration in P
type semiconductor.
ii) Discuss the application and properties of superconductors.
Unit V
Explain the different types of polarization mechanisms in dielectrics. Briefly explain the various dielectric breakdown mechanisms.
Discuss the following NDT methods.
i) X ray radiography
ii) Liquid Penetrant testing method.
i) Derive an expression for the internal field in a dielectric and hence deduce clausius-Mosotti relation.
ii)Explain the loss in dielectric materials
i) Describe the technique of nanophase synthesization.
ii)Draw block diagram of ultrasonic flaw detector with components.
i) Give detailed account of metallic glasses and their properties
ii) Explain the applications of bio materials.