Snehal-RTMNU-Engg-physics-sum18
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 -34JS
2. Velocity of light ‘C’ =3 ×10 8m/s
3. Charge on electron ‘e’ =1.602× 10-19 C
4. Mass of electron ‘m’ =9.11×10-31 kg
5. Avogadro’s constant ‘NA‘= 6.023×1026 atoms/k mole
6. Boltzman’s constant ‘K’= 1.380 ×10-23 JK -1
1. a) What is compton Effect? State the expression for compton shift. Explain the existence of
modified component in compton scattering.
b) Describe Davison – Germer experiment which supports the existence of matter waves.
c) An X-ray photon of wavelength 0.3Aº is scattered through an angle of 45º by a loosely
bounded electron. Find the wavelength of the scattered photon.
OR
2. a) What is de Broglie hypothesis? Show that how the quantization of angular momentum
follows from the concept of matter waves.
b) Prove that a free electron cannot absorb a photon completely.
c) A bullet of mass 50gm and an electron both travel with a velocity of 1200 m/s. What
wavelength can be associated with them?
3. a) Obtain an expression of quantized energy for an electron trapped in one dimensional
potential well of infinite height of width “L”.
b) What do you mean by phase velocity & Group velocity? Obtain the relation between
phase velocity and Group velocity.
c) An electron has a speed of 400 m/sec with an accuracy of 0.001%. Calculate the
uncertainty with which we can Locate the position of electron.
OR
4. a) State Heisenberg’s uncertainty principle. Describe a thought experiment to arrive at this
principle.
b) Show that electron can not exist inside the nucleus on the basis of uncertainty principle.
c) An electron confined to move in one- dimensional potential well of width 7Aº. Find the quantized energy values for the three lowest energy states.
5. a) Define:
i) Unit cell
ii) Coordination number
iii) Void space.
b) Show that FCC structure has maximum packing fraction among all cubic unit cells.
c) Lead crystallizes in FCC structure & it has a lattice constant of 4.95Aº. Calculate the
interplanar spacing d110, d111 and d220.
OR
6. a) Derive the relation between lattice constant and interplanar spacing in cubic unit cell.
b) What are Miller Indices? Draw the planes (100) and (111) for simple cubic structure.
c) Bragg angle corresponding to the first order reflection from the plane (111) in a crystal is 30º. When X-rays of wavelength 1.75 Aº are used, calculate interplanar spacing and lattice constant.
7. a) Explain the phenomenon of Hall effect and obtain an expression for Hall voltage for the extrinsic semiconductor.
b) Draw neat and clean energy band diagram of p-n junction diode in
i) Unbiased condition and ii) Forward bias condition.
c) Calculate the value of Hall voltage if observed Hall coefficient 5 m3/c for a current of 1mA flowing through the specimen of 20mm thickness placed suitably in a magnetic field of flux density 1.0 wb/m2.
OR
8. a) Explain the function of emitter, base and collector in a transistor.
b) Discuss the classification of solids on the basis of forbidden energy gap.
c) Draw energy band diagram of unbiased pnp transistor.
d) If the emitter current is 6 mA and the collector current is 5.75 mA. Calculate the value of D. C. current gain in common base mode.