Bangalore University 2007-2nd Sem B.E First/ , ruary/ch 05 - Question Paper
fNEWCHEME j Page No... 1- PHY12/22
USN First/Second Semester B.E Degree Examination, February/March 2005
Common to all Branches
Engineering Physics
Time: 3 hrs.] [Max.Marks : 100
Note: 1. Answer any FIVE full questions.
2. Value of Constants :
Electron mass m = 9.11 x 10~21 kg Electron charge e = 1.6 x 10 19C Velocity of light c = 3x 108m/s,*
Plancks constant h 6.625 x 10~34J.S
1. (a) Explain only the conclusions drawn in photoelectric effect and Davison Germer
experiment leading to de-Broglie hypothesis.
(b) Obtain an expression lor de-Broglie wavelength using the group velocity concept.
(c) Show that a free electron cannot exist in a nucleus of an atom.
, (d) An electron is confined to a box of length 10-8m. Calculate the minimum uncertainty in its velocity and comment oh the result. (5+7+4+4 Marks)
2. (a) What is the wave function? Give its physical significance and properties.
(b) A wave function is given by J = Asin(nU.x/L) for a motion of the particle in a zero potential well of breadth I . Calculate the value of A, where ~ is the position of the particle along L.
(c) Describe how cooper pairs are formed. What is the importance of cooper pairs in superconductivity?
(d) Give a brief account of high temperature superconductors. (5+5+6+4 Mar-.s)
| 3. (a) Bring out the salient features of Drude-Lorentz theory.
) (b) Obtain an expression for density of states oi energy levels.
(c) Show that if the probability of occupancy is a: at an energy level AC below the Fermi level, then x is also probability of non occupancy at an energy level AE above the Fermi level. (5+10+5 Marks)
4. (a! What is dielectric loss? Derive an expression for dielectric loss and discuss the frequency dependence of dielectric loss.
(b) A parallel plate capacitor has an area of 3 x 10~3m2 and the plates are separated
by a distance of 1mm. If a material with dielectric constant of 3.5 is introduced between the plates, determine the capacitance of the capacitor and electric field that must be applied for a charge of 20nC to be stored on each plate.
(c) Discuss the properties of soft and hard magnetic materials. Also mention two important applications of each. (7+5+8 Marks)
ContcL... 2
5. (a) Deduce expression for radiant energy density in terms of Einstein's coefficients
and discuss the need for population inversion.
(b) Explain the construction and working of He-Ne gas LASER with energy level diagram.
(c) Write a note on Holography. {7+8+5 Marks)
6. (a) Discuss the advantages and disadvantages of optical fiber communication
system over conventional communication system.
(b) The numerical aperture of an optical fiber is 0.2 when surrounded by air. Determine the refractive index of its core given the refractive index of cladding as 1.59. Also find the acceptance angle when it is in a medium of refractive index 1.33.
(c) Describe the construction and working of a Bragg's X-rav spectrometer and explain how it is used for determination of inter-planar spacing in a crystal.
(6+4+10'Marks)
7. (a) Discuss Bravais lattice and ciystal systems with the help of illustration.
(b) Explain the importance of Miller indices of direction and planes in crystallography.
(c) Calculate the coordination number and packing factor for SC, BCC and FCC structures.
(d) A current of 5mA flows in an X-ray tube operating under a potential of 10 kV. Calculate the rate at which the electron are bombarding the target and the maximum speed they could attain. (6+4+6*4 Marks)
8. (a) Discuss nano-technology system giving at least one application in detail.
(b) What ae the advantages and disadvantages of composite materials?
(c) Explain the term MEMS, Give a brief account of Smart materials. (7+5+8 Marks)
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| Earning: Approval pending. |
