Download SGBAU B-Tech 1st Sem Chemical Engineering Applied Physics Question Paper

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B.Tech.(Chemical Engineering) (Sem-II) Examination December-2017

Applied Physics-I

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Pages: 2 AW - 3533

Max. Marks : 40

Time : Two Hours

Notes : Due credit will be given to neatness and adequate dimensions.
Assume suitable data wherever necessary.

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List of constants:

1. Electron mass m=9.1x 10^-31 kg
2. Electron charge e = 1.6 x 10^-19 C.

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3. Velocity of light c =3 x 10⁸ m/s
4. Planck's constant h = 6.63 x 10^-34J.s.

1. a) Derive an Expression for conductivity in intrinsic semiconductor. 4
   b) Explain the classification of conductor, semiconductor and insulator on the basis of conduction band, valence band and energy band gap. 4
   c) What is LED? Explain why LED emits light. 3
   

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   d) LED emits yellow light of wavelength 5880A°. Calculate the energy band gap for the material. 3

   OR

2. a) Explain the working of Transistor in CE mode with suitable diagram. 4
   b) Define: 3
   1. Depletion Layer.
   2. Photo diode.

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   3. LDR.
   c) Explain the formation of energy bands in solid with help of band theory of solid. 4
   d) Calculate the mobility of electron in copper, if electrons per unit volume is 8.496 x 10²² cm^-3 and resistivity of copper is 1.7 x 10^-8 ohm-cm. 3
3. a) What is packing fraction? Calculate the packing fraction in BCC and FCC structure. 4
   b) What is Bravais lattices? Write in tabular form. 4
   

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   c) Define liquid crystal. State any four applications of liquid crystal. 3
   d) KCl crystal which has FCC lattice structure has a density of 1980 kg/m³. If its molecular weight is 74.55 amu. Find it's lattice constant. 2

   OR

4. a) What are Miller indices? Explain. 4
   b) What is coordination number? Show that the coordination number for BCC and FCC structure is 8 and 12 respectively. 3
   

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   c) Explain Schottky defect and Frenkel defect with suitable diagram. 4
   d) Distinguish between crystalline solid and amorphous solid 2
5. a) Describe Davission — Germer experiment of electron diffraction. Discuss how it explain the wave nature of electron. 6
   b) Show that De-Broglie wavelength of a particle of rest mass m₀ and kinetic energy K which is not negligible compared with m₀c² is given by. 4
   λ = h / √(K² + 2m₀c²K)
   

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   c) Show that electron does not present inside the nucleus using Heisenberg's uncertainty principle. 5

   OR

6. a) Derive Planck's law of black body radiation. 6
   b) The uncertainty in position of electron is 5x10^-10 m. Find the uncertainty in it's momentum. 3
   c) State and Explain Einstein's photoelectric equation. 4

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