BSc Physics SEM III 2022 2023 Oct 2023 PHYSICS 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 absorption coefficient of sound is
   • (ii) The refractive index of core of optical fiber 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
   • (iii) Example of crystal with perfect covalent bonding is
   • (iv) The number of symmetry elements to a cubic crystal is
   • (v) In electromagnetic spectrum, compared to visible light, the x-rays have
   • a) The wavelength is smaller and the energy is higher
   • b) The wavelength is larger and the energy is larger
   • c) The wavelength is smaller and the frequency is lower
   • d) The energy and frequency both are lower
   • (vi) Liquid crystal display is actually a combination of two states of matter
   • a) Solid-solid b) solid-liquid c) liquid-liquid d) none of these
2. Q1 (B) Answer in one statement: What is metastable state? 3 marks
   • (ii) Define primitive cell
   • (iii) Define resistivity Fill in the blanks: (05)
   • (i) Through holography we can produce dimensional images of objects
   • (ii) The refractive index of core of an optical fiber than cladding material
   • (iii) The SI unit of conductivity is 7 S.Y.B.Se. Physics-III Hrs:3 Marks :10 j (iv) Above Curie temperature, ferromagnetic substance converts into
   • (v) The number of atoms per unit cell in FCC structure is
3. 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 minimized?
   • (ii) With the help of a neat labeled diagram of optical resonator explain the basic principle of laser. Also explain the process of amplification
4. Q2 (B) Attempt any one: 8 marks
   • (i) Describe the structure of a step-index optical fiber. Explain the propagation of light through
   • (ii) Define absorption coefficient of a material and hence determine the relation between reverberation time of a hall and absorption coefficient,
5. Q2 (C) Attempt any one: 4 marks
   • (i) The room has wall area 200 m’, the floor aréa is 180 m? and the ceiling area is 180 The volume of the auditorium is 845 . The average sound absorption coefficient for the walls is
   • 0.028, for ceiling is 0.65 and for the floor 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 angle in air; and the critical angle for core/cladding interface
6. Q3 (A) Attempt any one: 8 marks
   • (i) Show that in cubic crystal the distance between adjacent planes with miller indices (hkl) is given by, = a/ (h?-+k where a is the lattice constant (1i) Discuss the crystal structures of diamond, cesium chloride, sodium chloride and zinc
7. Q3 (B) Attempt any one: 8 marks
   • (i) Obtain distribution of atoms in the atomic planes of simple cubic crystal for (010),(1 10)
   • (ii) What is a structure? Explain with suitable diagram the HCP and FCC close
8. Q3 (C) Attempt any one: 4 marks
   • (i) Copper has FCC structure and its atomic radius is calculate the interplanar spacing for the (111) and (321) planes
   • (ii) The lattice constant of the unit cell of a bcc structure is 0.287 nm. Find the number of of the planes (100), (110) and (111) / Q.4. (A) Attempt any one: (08)
   • (i) Mention any four important characteristics of semiconducting materials and any two
   • (ii) Explain hysteresis curve of ferromagnetic materials on the basis of domain theory
9. Q4 (B) Attempt any one: 8 marks
   • (i) How the materials are classified according to their magnetic properties? Explain
   • (ii) Mention any four important characteristics of insulating materials and any two applications
10. Q4 (C) Attempt any one: 4 marks
    • (i) What is the difference between intrinsic and extrinsic semiconductors?
    • (ii) Differentiate between soft and hard magnetic materials. =
11. Q5 Attempt any four: 20 marks
    • (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 X-X-X- Best of Luck —X-X-X

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