BSc Physics SEM III 2019 2020 Oct 2020 PHYSICS PAPER III Question Paper - Mumbai University | munotes

Questions asked in this paper

• (2) Figures to the right indicate maximum marks

1. Q1 (A) Choose correct alternative in each of the following: 12 marks
   • (i) The unit of absoption coefficient of sound is
   • (ii) The refractive index of core of optical fibre is
   • a) Larger than that of cladding material
   • b) Smaller than that of cladding material
   • c) Equal to the refractive index of cladding material
   • d) None of these (ili) Example of crystal with perfect covalent bonding is magnetic material to be used for data storage should have
   • c) and low coercivity
   • d) None of these
   • (v)The magnetic moment of any electron is always
   • a) Less than Bohr magneton
   • b)Greater than bohr magneton
   • c) Both (a) and (b)
   • d) Equal to bohr magneton
   • (vi) Liquid crystal display is actually a combination of two states of matter
   • a) solid-liquid none of these
2. Q1 (B) Answer in one statement; 3 marks
   • (i) What is metastable state?
   • (i) Define primitive cell
   • (iii) Define resistivity
3. Q1 (C) Fill in the blanks: 5 marks
   • (i) Through holography we can produce images of objects
   • (ii) The refractive index of core of an optical fibre Cladding material
   • (iii) The SI unit of conductivity is ‘
   • (iv) The magnetic moment of any electron is always than Bhor magneton
   • (v) The number of atoms per unit cell in FCC Structure is
4. Q2 (A) Attempt any one: 8 marks
   • (i) What is meant by reverberation and reverberation time?explain the Causes to form reverberation in a hall. How it can be minimised?
   • (ii) With the help of a neat labelled diagram of optical resonator explain the basic Principle of laser. Also explain the process of amplification,
5. Q2 (B) Attempt any one: 8 marks
   • (i) Describe the Structure of a optical fibre. Explain the Propogation of light through Define absorption coefficient of a material and hence determine the relation between reverberation time of a hall and absorption coefficient Attempt any one: (04)
   • (i) The room has wall area 200 the floor area is 180 and the ceiling area is 180 The Volume of the auditorium is 845 m? The average sound absorption coefficient for the walls is
   • 0.028, for ceiling is 0.65 and for the is 0.06 Calculate the average sound absorption coefficient and the reverberation time
   • (ii) The core and the cladding of an optical fibre have refractive indices 1.432 and respectively. Find the acceptance angle in air: and the angle for Core/cladding interface Attempt any one: (08)
   • (i) Show that in crystal the distance between adjacent planes with miller indices (hkl) is given by, = a/ where a is the lattice constant
   • (ii) Discuss the crystal structures of diamond, caesium chloride, sodium chloride and zine
6. Q3 (B) Attempt any one: 8 marks
   • (i) Obtain distribution of atoms in the atomic planes of simple cubic crystal for (010),(110)
   • (ii) What is a close-packed structure? Explain with suitable diagram the HCP and FCC close
7. Q3 (C) Attempt any one: 4 marks
   • (i) Copper has FCC structure and its atomic radius is the interplanar spacing for the (111) and (321) planes
   • (ii) The lattice constant of the unit cell of a bec structure is 0.287 nm. Find the number of of the planes (100), (110) and (111)
8. Q4 (A) Attempt any one: 8 marks
   • (1) Mention any four important characteristics of semiconducting materials and any two (i1) Explain hysteresis curve of ferromagnetic materials on the basis of domain theory
9. Q4 (B) Attempt any one: 8 marks
   • (1) How the materials are classified according to their magnetic properties? Explain (1i) Mention any four important characteristics of insulating materials and any two applications
10. Q4 (C) Attempt any one: 4 marks
    • (i) A metal wire has a resistance of 2.52 Q at C. if its temperature coefficient of resistance is find the resistance of wire at 55 Find the relative permeability of ferromagnetic material if a magnetic field of strength 220 A/m produces magnetization of 3300 A/m in it
11. Q5 Attempt any four:
    • (i) State the factors affecting the acoustics of building
    • (ii) Explain the applications of fibre optics
    • (iii) Explain crystal lattice and miller indices
    • (iv) What is a bravis or space lattice? How is it related to crystal structure?
    • (v) Write a note on dielectric materials
    • (vi)Compare paramagnetic and ferromagnetic materials.

Read from the scan above, so a character or two may differ. The scan is the original.