(b) What is the essential difference between interference and diffraction of light ? How can you achieve Fraunhofer diffraction in the laboratory ? Using the concept of Fraunhofer diffraction at a single slit, find out the intensity distribution produced by two slits of equal width.
(c) Explain how Einstein's A and B coefficients are related to the phenomena of spontaneous and stimulated emission of radiation, respectively. Derive the relation between A and B. Establish that at very high frequency around X-ray wavelength regime, lasers cannot be made as easily as at low frequencies, e.g. far infra-red regime.
(d) Drawing a neat diagram, discuss how light travels through an optical fibre. Show that the numerical aperture of a commercially available optical fibre is around 0.25. Explain its physical significance.
(b) Show that the mass-energy relationship in relativistic kinematics can lead to the equation E^2 = c^2 p^2 + m_0^2 c^4 where E is the total energy of the particle of rest mass m_0, linear momentum p and moving with a velocity v; c is the velocity of light in free space.
(b) What are constraints of motion ? Explain with examples the holonomic and non-holonomic constraints. Discuss critically how can one overcome the limits of constraints by introducing generalised coordinates.
(a) How are linear and angular momenta related to each other ? Considering a system of mass points under the influence of forces derived from potentials only, prove that the generalised linear momentum is conserved. Establish further that the angular momentum of the above system is also conserved if the potential is centrally symmetric.
Show that the condition of periodicity of lattice leads to the Bloch theorem. What is a Bloch function ?
A transistor with \beta = 50, V_{BE} = 0.7\text{ V}, V_{CC} = 22.5\text{ V} and R_c = 5.6\text{ k}\Omega is used in biasing circuit as shown in the figure. It is designed to establish the quiescent potential at V_{CE} = 12\text{ V}, I_C = 1.5\text{ mA} and stability factor S \le 3. Find the values of resistors R_E, R_1 and R_2, where symbols have their usual meanings.
(i) The following information is included on the data sheet for an N-channel JFET : I_{DSS} = 20\text{ mA}, V_p = -8\text{V} and g_{mo} = 5000\text{ }\mu\text{s} Determine the value of drain current and trans-conductance at V_{GS} = -4\text{ V}.
What is the principle used in 'half-adder' ? Give the truth table for it.
Give the two forms of the De Morgan's theorem.
Draw a circuit diagram of an R-C phase shift oscillator. Explain its working. Derive an expression for its frequency.
Describe in detail one experiment for the detection of neutrino.
Write down the Bethe-Weizsäcker mass formula. Explain various terms of the formula.
(i) Write the Weizsacker mass formula and explain the significance of various terms. (ii) Determine the amount of {}_{84}^{210}\text{Po} necessary to provide a source of \alpha-particles of strength 5\text{ mC}_i. The half-life of {}_{84}^{210}\text{Po} is 138\text{ d}.
(i) Which of the following reactions are allowed and forbidden under the conservation of strangeness, conservation of baryon number and conservation of charge ? \pi^+ + n \rightarrow \Lambda^\circ + K^+ \pi^+ + n \rightarrow K^\circ + K^+ \pi^- + p \rightarrow \Lambda^\circ + K^+ \pi^- + p \rightarrow \pi^\circ + \Lambda^\circ (ii) By drawing E vs. \vec{k} curve, distinguish between metal, insulator and semiconductor.
Explain how energy is released in stars.
