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 reverberation time is
   • a) Directly proportional to surface area and its absorption coefficient
   • b) Directly proportional to volume of the hall and inversely proportional to surface area Inversely proportional to volume of the hall and directly proportional to surface area
   • d) Inversely proportional tc volume and surface area and directly proportional to
   • (iii) He-Ne laser is
   • (iv) Example of crystal with perfect covalent bonding is
   • (v) AMOLED stands for {vi) Liquid crystal display is actually a combination of two states of matter
   • a) Solid-solid b) solid-liquid d) none of these
2. Q1 (B) Answer in one statement: : (i) State sabine’s formula 3 marks
   • (ii) Define viscosity
   • (iii) What is LEDs?
3. Q1 (C) Fill in the blanks: (05) \
   • (i) Through holography we can produce dimensiona! images of objects
   • (ii) The refractive index of core of an optical fibre than Cladding material
   • (iii) Diffusion rate is inversely proportional to
   • (iv) Magnetic hysteresis is a property which affects materials
   • (v) The magnetic moment of any electron is Bhor magneton
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) Describe the construction and working of a He-Ne laser.draw energy level diagram
5. Q2 (B) Attempt any one: 8 marks
   • (i) What is numerical aperture (NA) of an optical fiber? Derive necessary expression for NA
   • ii) Define absorption coefficient of a material and hence determine the relation between reverberation time of a hall and absorption coefficient,
6. Q2 , (C) Attempt any one: 4 marks
   • (i) The capacity of a hall is 3398.4 m? and its total absorption equals 92.90 of open window. Entry of people inside the hall raises the absorption by 185.80 m? What is the change in reverberation time?
   • (ii) The laser beam is targeted on the moon. A laser of wavelength 7200 and aperture
   • 0.045 m is used for it. If the mcon is at a distance of about 4 x Km from the earth, find a) the angular spread of the beam and b) the axial spread when the laser reaches the surface of the moon. Neglect the earth’s atmospheric effect
7. Q3 (A) Attempt any one: 8 marks
   • (i) What are biological fluids? Enlist them. Give physical-chemical properties of any one
   • (ii) What is action potential? State different types of action potential
8. Q3 (B) Attempt any one: 8 marks
   • (i) State and explain Nernst equation
   • (ii) State and explain Fick’s law of diffusion
9. Q3 (C) Attempt any one: 4 marks
   • (i) Explain diffusion across biological cell membrane (il) Give viviogical importance of surtace tension
10. Q4 (A) Attempt any one: 8 marks
    • (i) How the materials are classified as per their structures? Explain each type
    • (ii) What is meant by OLED? Explain construction and working of OLED panel
11. Q4 (B) Attempt any one: 8 marks
    • (i) How the materials are classified according to their magnetic properties? Explain
    • (ii) Explain the phenomena of refraction, reflection, absorption and transmission taking place when is made incident on matter
12. Q4 (C) Attempt any one: 4 marks
    • (i) Write a note on pyroelectric materials
    • (ii) Explain polymers and composite materials
13. Q5 Attempt any four: 20 marks
    • (i) State the factors affecting the acoustics of building
    • (ii) Give brief account of application of laser
    • (iii) Explain in brief Hodgkin-Huxley model of action potential
    • (iv) Write a note on membrane channels
    • (v) Write a note on thin films
    • (vi) Differentiate between soft and hard magnetic materials

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