# Dr MGR Educational and Research Institute 2009 B.E Information Science and Engineering Model -2 (EEE) , PH 231 Materials Science - Question Paper

Sunday, 16 June 2013 07:15Web

ans ALL ques. MAXIMUMUM MARKS 100

Part-a 10*2=20

**1.**elaborate Bravais lattices?

**2.**X-ray of wavelength 1.2 Angstrom are diffracted by (1

**10)**planes in a crystal at an angle 30 degree in the 1st order. compute the inter atomic spacing.

**3.**describe Fermi level.

**4.**compute the energy difference ranging from the least energy level and next possible higher energy level of an electron confined in a box of size one nm.

**5.**With increase of temperature the conductivity of semiconductor increases while that of matter reduces. provide reasons.

**6.**discuss the concept of hole in semiconductor.

**7.**What is bohr magneto?

**8.**elaborate various dielectric breakdown mechanisms.

**9.**Distinguish fluorescence and phosphorescence.

**10.**compute the wavelength of radiation emitted by an LED made up of a semiconductor material with band gap energy 2.8 eV.

Part-b 16*5=80

11

**(**elaborate miller indices? Derive an expression for the interplanar spacing for (hkl) planes of a cubic structure.

**a)****(**for a NaCl crystal, 1st order reflection maxima occurs at 5.9 degre

**b)****e.**8.4 degree and 5.2 degree for (100), (1

**10)**and (1

**1**planes respectively. Prove that NaCl belongs to FCC structure.

**1)**12

**(**Derive an expression for the density of states and based on that compute the carrier concentration in metals.

**a)**(Or)

**(**discuss superconducting phenomen

**b)****a.**elaborate its properties ? Distinguish kind type one and kind two super conductors.

13

**(**discuss the mechanism of intrinsic conduction in semiconductors. Derive an expression for conductivity of an intrinsic semiconductor in terms of carrier concentration and carrier mobility.

**a)**(Or)

**(**What is Hall coefficient ? Derive an expression for Hall coefficient. define an experimental setup for the measurement of the identical.

**b)**14

**(**provide an account of Weiss theory of ferromagnetism and show from the plot of Langevin function, spontaneous magnetization exists ranging from the curie temperature and vanishes above the Curie temperature.

**a)**(Or)

**(**What is meant by local field in dielectric and how is it computed for a cubic structure? Deduce the Claussic-Mosotti relation.

**b)****1**Write an essay on thermography. What is its application?

**5.**Earning: Approval pending. |