Punjab Technical University 2011-1st Sem B.Tech B Tech ester, , Physics , Reappear , - Question Paper

Time: three Hours
Maximum Marks: 60

Instruction to Candidates:
1) Section- A is Compulsory.
2) Attempt any 5 ques. from Section- B & C
3) choose at lowest 2 ques. from part - B & C

part – A [Marks 2*10=20]

Q1) a) Enumerate various polarization mechanisms in dielectrics?

b) Iron is a ferromagnetic material but a piece of iron does not ordinarily behave as a magnet. discuss.

c) discuss the meaning of stimulated emission.

d) Bring out the differences ranging from step-index and graded-index fibers.

e) What is the electric flux through a closed surface surrounding an electric dipole? discuss.

f) Is the earth an inertial frame? If not, why?

g) Write the Braggs formula for X-ray diffraction and discuss the meaning of different symbols in it.

h) What is the method of pumping in a Ruby laser?

i) State the conditions which a physically acceptable wave-function must obey.

j) Mention a few important modifications that occur in substances when they change from their normal state to the superconducting state.

part – B [8 Marks each]

Q2) a) Write down the 4 Maxwells equations in differential form. explain the significance of
each. discuss Maxwells modification of Amperes legal regulations.

b) Dielectric constant of a gas at NT.P. is 1.00074. If the gas is held in an external field of three x 104 V/m, compute the dipole moment of every atom of the gas.

Q3) a) elaborate the distinguishing characteristics of ferromagnetism? explain the domain theory of ferromagnetism.

b) The magnetic susceptibility of silicon is -4.2x10-6. obtain its magnetization and the magnetic
flux density when it is placed in magnetic field of strength 1.2x105 A/m.

Q4) a) elaborate Einsteins coefficients? discuss their meaning and derive the relation ranging from them.

b) What is a hologram? How is it produced and how is the image reconstructed from it?

Q5) a) What is an optical fiber? discuss the meaning of the terms:
1) Acceptance angle
2) Numerical aperture
3) Normalized frequency
4) Fractional change in refractive index

b) The core diameter of a graded index fiber is 0.05 mm and its numerical aperture is 0.22. If it carries light of wavelength 850 nm, what is the normalized frequency and what is the maximum number of modes that can be propagated through the fiber?

part – C [8 Marks each]

Q6) a) What was the objective of conducting the Michelson Morley experiment? define the experiment. How do you interpret its result?

b) A spaceship moving away from earth with velocity 0.6c fires a rocket whose velocity relative to the spaceship is 0.7c away from the earth.
What will be the velocity of the rocket, as observed from the earth?

Q7) a) What is Moseleys legal regulations and what is its significance? How do you discuss it on the basis of Bohrs theory?

b) The 1st order diffraction of X-rays is obtained to occur from a crystal at a glancing angle of 9°. compute the wavelength of the X-rays and the glancing angle for their 2nd order diffraction if the inter-planar spacing in the crystal is 2.51 Å.

Q8) a) What is the difference ranging from phase and group velocities? Show that the wave group associated with a particle moves with the velocity of the particle. Also obtain a relation ranging from the phase and group velocities.

b) X-rays of wavelength 0.144 Å are scattered from a graphite block. obtain the maximum shift in their wavelength and the maximum energy imparted to the recoil electrons.

Q9) a) What is Meissner effect? discuss the difference ranging from Type-I and Type-II superconductors.

b) Determine the critical temperature for aluminium if the magnetic flux penetration depths for aluminium are 16 nm and 96 nm at 2.18 K and 8.1 K, respectively.

Earning:   Approval pending.