Tiêu đề Physics.pdf ✅

Physics-1 Subject Code -A000111(015) Question Bank Unit 1 Q.No. Laser and Optical fiber Marks 1 What are laser characteristics? Describe principle and working of He-Ne Laser. Why is a long narrow discharge tube used in He-Ne laser? 8 2 Explain construction and working of Ruby Laser and discuss its drawbacks. Write any two applications. 8 3 (a) Give construction and working of ND: YAG laser. (b) What is population inversion? Explain why laser action cannot occur without population inversion between atomic levels? 4 4 4 Give construction and working of Semiconductor lasers. 8 5 Explain with neat diagram absorption, spontaneous emission and stimulated emission of radiation. What is the reason for the monochromaticity of laser beams? 8 6 Give the principle of propagation of light through an optical fiber. Derive an expression for acceptance angle , acceptance cone and Numerical Aperture. 8 7 What is optical fiber? Explain the types of fiber on the basis of modes and their index profiles with a neat diagram wherever required. 8 8 (a)A step index fiber in air has a NA=0.16, a core refractive index of 1.45 and a core diameter of 60cm. Determine the normalized frequency for the fiber when light of wavelength 0.9μm is transmitted. (b)An optical fiber is made of glass with a refractive Index of l.55 and is clad with another glass with a refractive index of 1.51. Launching takes place from air : (i) What numerical aperture does the fiber have? (ii)What is the acceptance angle? 4 4 9 (a)What do you understand about Optical Resonator? (b) Find the intensity of a laser beam of 10mW power and having a diameter of 1.3mm. Assume the intensity to be uniform across the beam. 4 4
10 (a) An optical power of 1MW is launched into an Optical Fiber of length 100 m. If the power emerging from the end is 0.3MW calculate the fiber attenuation. (b) (a)A pulsed laser is constructed with a Ruby crystal as the active element. The Ruby rod contains a total of 3x1019 Cr+3 ions. If the laser emits light at a wavelength of 6943A0 , find the energy of one emitted photon and the total energy available per pulse. (c) A laser beam can be focused on an area equal to the square of its wavelength (λ2 ). For a He- Ne laser λ = 6328 A0 . If the laser radiates energy at the rate of 1mW, find out the intensity of the focused beam. 3 3 2 Unit 2 Q.No. Semiconductor Marks 11 What do you mean by p-n junction? Describe the formation of depletion region and working pn junction diode in forward and reverse bias with neat labelled diag. 8 12 Write a short note on: (1) law of mass action (2) Charge neutrality condition (3) N type and P type semiconductor (4) Drift and diffusion current 8 13 Draw energy band diagram for n type semiconductor at 0 K and at room temperature. Show that at 0 K fermi level lies midway between valence band and conduction band. 8 14 Explain the formation of depletion region in PN junction diodes and hence derive the expression for potential barrier. 8 15 What is pn junction? describe its forward and reverse biased characteristics with an energy band diagram. 8 16 Derive the expression for electron concentration in an intrinsic semiconductor. 8 17 What are intrinsic semiconductors? Derive the expression for intrinsic concentration ni of a semiconductor. 8 18 (a) Explain the variation in position of fermi level with temperature in both n and p type semiconductors. (b) Explain how n and p type semiconductors are formed with the help of energy band diagrams. 4 4 19 (a) What is the effect of impurity concentration on the fermi level? Explain for both p- type and n- type semiconductor. (b) Difference between intrinsic and extrinsic semiconductors. 4 4 20 Derive the expression for hole concentration in an intrinsic semiconductor. 8
Unit 3 Q.No. Solid Electronic Materials Marks 21 Explain the formation of energy band in solids, on this basis explain the distinction between metals, insulators and conductors along with a neat diagram. 8 22 (a) What are direct and indirect energy bands in solids? (b) Explain the terms: carrier mobility and drift velocity 4 4 23 Write and explain Fermi – Dirac function. How does it vary with temperature? 8 24 Explain the quantum theory of free electrons in metals. Derive an expression for density of energy states in it. 8 25 What is the effect of periodic potential on the energy of electrons in metal? Explain it on the basis of the Kronig – Penny model and explain the formation of energy band. 8 26 (a) A rectangular block of a solid is connected to a dc voltage source. Obtain the expressions for (i) the current density flowing through the block and (ii) the conductivity of the material in terms of concentration of carriers in it. (b) In a solid consider the energy level lying 0.01 eV below Fermi level. What is the probability of this level not being occupied by an electron? 4 4 27 (a) The energy of a photon of sodium light (λ= 589 nm) equals the band gap of a semiconductor material. What will be the minimum energy E required to create hole electron pair? (b) Fermi energy of a given substance is 7.9 eV. What is the average energy and speed of electrons in this substance at 0 K. 4 4 28 (a) In a solid, consider the energy level lying 0.02 eV below the fermi level, calculate the probability of this not being occupied by electrons at room temperature (300 K). Given k = 1.38 X 10-23 J/K. (b) Define: fermi energy, conduction band, valence band, density of states. 4 4 29 (a) For sodium electron concentration is 2.65 X 1022 cm-3 . Find the value of fermi energy. (b) The fermi level for potassium is 2.1 eV. Calculate the velocity of the electrons at the fermi level. 4 4
30 Discuss the Kronig-Penney model for the motion of an electron in a periodic potential and hence explain E-K curve in solids. 8 Unit 4 Q.No. Quantum Mechanics Marks 31 (a)What is a matter wave .Derive the expression for it and discuss the significance of change in mass and velocity on it. (b) Describe Davisson and Germer Experiment. What does it confirm? 4 4 32 Derive time independent Schrodinger wave equation. 8 33 Derive time dependent Schrodinger wave equation. 8 34 State and prove Heisenberg’s uncertainty principle. Explain its consequence with examples. 8 35 Derive one dimensional Shrodinger wave equation for a particle in a box and hence find energy eigenvalue for it. 8 36 (a) Explain the consequences of Heisenberg’s uncertainty principle with an example. (b) Calculate the uncertainty in measurement of momentum of an electron if the uncertainty in its location is 1Å. 4 4 37 (a) What is a wave packet? explain Born interpretation. (b) Calculate the energy required for an electron to jump from ground state to the second excited state in a potential well of width L. 4 4 38 (a) Explain with the help of uncertainty principle why electron cannot reside inside the nucleus. (b) Write the properties of wave function . 4 4 39 Derive expression for energy eigen value and normalized eigen function for a particle trapped in one dimensional infinite potential well of width a. 8 40 (a) Uncertainty in time of an excited atom is about 10-8 sec. what are the uncertainty in energy and in the frequency of radiation. (b) Explain the expectation values of the dynamical variables. 4 4