B.E. First Semester All Branches (C.B.S.) / B.E. First Semester (Fire Engineering)

Engineering Physics

1. Planck’s constant ‘h’= 6.63 ×10 ^{-34}JS

2. Velocity of light ‘C’ =3 ×10 ^{8}m/s

3. Charge on electron ‘e’ =1.602× 10^{-19} C

4. Mass of electron ‘m’ =9.11×10^{-31} kg

5. Avogadro’s constan ‘N_{A}‘= 6.023×10^{26} atoms/k mole

6. Boltzman’s constant ‘K’= 1.380 ×10^{-23} JK ^{-1}

1. a) What is Compton effect? Why classical theory failed to explain it?

b) In case of high atomic no. scatterer element intensity of unmodified wavelength is higher than that of modified wavelength. Explain.

c) X-rays of initial wavelength 0.5 ×10^{-10} m undergo Compton Scattering. Find the scattering angle at which wavelength of scattered X-rays will be greater than that of incident wavelength by one percent?

OR

2. a) What is de-Broglie hypothesis? Obtain an expression for wavelength associated with an electron accelerated through a potential difference of ‘V’ volts.

b) Show how the Bohr’s quantization condition of angular momentum follows the concept of matter waves.

c) Calculate de-Broglie wavelength of the orbital electron of Hydrogen atom. (Given that energy of electron is 13.6 eV)

3. a) Derive an expression for wave function of an electron confined to move in an infinite potential well of width ‘L’.

b) What is a wave packet?

c)Find the lowest energy of an electron in one dimensional potential well of width 2A^{0} .Express the result in electron volts.

OR

4. a) Discuss a thought experiment of electron diffraction to arrive at Heisenberg uncertainty principle with suitable diagram.

b) Define phase velocity and group velocity.

c) Calculate uncertainty in location of an electron and a ball of mass 1 kg if their velocities are 10^{5} s/m and 10 m/s respectively.

5. a) Derive expression for atomic radius and atomic packing fraction (A.P.F.) for BCC and FCC structures and show that percentage void space is more in BCC compared to FCC structure.

b) Molybdenum has BCC structure. Its density is 10.2×10^{3} kg /m^{3} and its atomic wt. is 95.94. Determine radius of Molybdenum atom.

OR

6. a) What are Miller Indices? Draw the crystal planes in simple cubic structure having Miller Indices (i) (102) and (ii) (0 10).

b) State and derive Bragg’s Law of X-ray diffraction.

c) The d_{110} interplaner spacing in a BCC metal vanadium is 2.15A^{0}. Find its lattice constant (a).

7. a) Explain classification of solids on the basis of energy band diagrams.

b) Draw energy band diagrams for the following :

i) PN Junction in Reverse Bias

ii) NPN Transistor (unbiased)

c) Find V_{0} across a silicon junction at room temperature, if p-region has 10 ^{ 21 }acceptor atoms /m^{3} and N-region has 10^{22} atoms /m^{3} .

OR

8. a) What is Hall effect? Obtain an expression for Hall voltage if p-type semiconductor material is used.

b) What is meant by depletion region?

c) Determine the probability of an electron thermally excited into the conduction band in Germanium at 27ºC, if the energy gap is 0.72 eV.

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