Gujarat Technological University 2009 A.M.Ae.S.I Aeronautical Engineering Physics - Question Paper

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Q.1 (a) discuss the method to determine the absorption coefficient of material.
(b) A liquid column subjected to ultrasonic waves constitutes an acoustical
grating, discuss.
(c) Why Miller indices are reciprocals of the intercepts of the plane along the
three axes?
(d) Show that the superconductors are perfectly diamagnetic in nature.
(e) 3 level laser system is rare whereas 4 level system is common, discuss.
(f) Why nano materials exhibit various physical properties of materials from
those at a large scale?
(g) State the requirements for infinite bandwidth optical fiber link.
Q.2 (a) Distinguish ranging from
(i) Spontaneous Emission and Stimulated Emission
ii) Monomode and Multimode optical fiber
(b) i) Draw circuit diagram of oscillator (Pierce's) and discuss
magnetostriction method to produce ultrasonic waves.
ii) compute the length of an iron rod which can be used to produce
ultrasonic waves of 20 KHz. Density of iron is 7.23 x 103 kg/m3 and Young's modulus is 11.6 x 1010N/m2
Q.3 (a) Draw the diagram of variation of electron energy as a function of interatomic
spacing; discuss the formation of energy bands in a solid. Also discuss how it
helps to classify the materials into conductors, semiconductors and insulators?
(b) The Hall coefficient of a semiconductor is 3.22 x108 four m3 C8 one and its resistivity is nine x 108 3
;8m. compute concentration and the mobility of the charge carrier. Given: e = 1.6 x 108 19 C.
OR
Q.3 (a) Silicon and Germanium are not suitable for LED's, discuss. (b) explain the dependence of critical magnetic field and London penetration depth on temperature.
compute the mean free path ranging from collisions of the free electrons in copper
at 20 C°. The resistivity of copper at 20 C° is 1.27 x 108 3;8m and density of free electrons is 8.48 x 1028 m8 305
Given: e = 1.6 x 108 19, m = 9.11 x 108 31 kg and kB = 1.38 x 108 23 JK8 one

Q.4 (a) Show that the ratio of Einstein A coefficient for spontaneous emission to that
of Einstein B coefficient for stimulated emission is provided by 8ph?3/C3.
(b) discuss self focusing property of Graded Index optical fiber.
(c) A refractive index of core for step index fiber is 1.52, diameter is 2.9 Im and a
fractional difference of refractive index is 0.0007. It is operated at a
wavelength of 1.3 Im. obtain the number of modes the fiber will support.
Q.4 (a) Draw the schematic diagram of hologram construction and discuss the
formation hologram.
(b) Derive the expression of the numerical aperture of step index optical fiber.
Show that it does not depend on the physical dimensions of the fiber.
(c) obtain the core radius, of step index fiber, necessary for single mode operation at
850 nm. The refractive indices of core and cladding are 1.48 and 1.47
respectively.
Q.5 (a) explain the melt spinning process technique for preparing metallic glasses. 05
(b) discuss working of ultrasonic flow detector. 05
(c) The ultrasonic pulse8echo is used to locate the position of defect in a steel bar
of 40 cm thick. If pulse arrival times form defective and non defective portion
are 30 Is and 80 Is respectively. compute the distance of defect from the top
surface.
Q.5 (a) discuss Shape Memory effect and Pseudo Elastic effect. 06
(b) Why clean surfaces are needed for surface and subsurface defect detection
incase of liquid penetration NDT method?
(c) State and discuss the factors to choose a biomaterial for prosthetic device. 04

Earning:   Approval pending.