Rajasthan Technical University 2009-2nd Sem B.Tech(Main) Engineering Physics-II - Question Paper

Unit - I

1. Explain what do you understand by the terms potential well and potential barrier. How does a particle with energy lower than the barrier height tunnels through its quantum mechanically ? provide 1 example.
OR
a. Calculate Fermi energy in copper assuming that every copper item contributes 1 free electron to the electron gas. provided density of copper 8.94 X 103 kg/m3 and atomic mass 63.5u.
b. Electrons of energy leV and two eV are incident on a potential barrier of height five eV and width 5A. obtain tunnel probability for these electrons.

Unit – II
1. Explain essential requirements for producing laser action. How are these requirements found in case of Rube laxer? Draw diagram of Ruby laser to discuss it.
OR
What do you understand by spontaneous emission and stimulated emission. find a relation for Einstein coefficients A and B for spontaneous and stimulated emission.

Unit – III
1. How does monochromatic relate to temporal coherence ? describe the "Q" factor for a spectral line.
OR
compute the refractive indices of core and cladding materials of an optical fiber if its numerical aperture is 0.22 and relative refractive index difference is 0.012.

Unit – IV
1. Explain the terms avalanche, quenching and dead time. How is quenching achieved in a G.M. tube?
OR
provide the construction and theory of a scintillation counter.

Unit – V
1. Given f(x,y,z)=x2+2y2+3xy2+5z2 obtain grad f(x,y,z), identical as del f.
OR
obtain (a) del . r (b) del . r where /r/ = r and r = (x,y,z).

Earning:   Approval pending.