Question Paper: Physics : Question Paper Dec 2011 - First Year Engineering (Semester 1) | Gujarat Technological University (GTU)
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Physics - Dec 2011

First Year Engineering (Semester 1)

TOTAL MARKS: 100
TOTAL TIME: 3 HOURS
(1) Question 1 is compulsory.
(2) Attempt any four from the remaining questions.
(3) Assume data wherever required.
(4) Figures to the right indicate full marks.
1(a)(i) Name characteristics of musical sound.(1 marks) 1(a)(ii) The frequency of ultrasonic waves is _______(1 marks) 1(a)(iii) Define unit cell.(1 marks) 1(a)(iv) Give one one example of pentavalent impurity and trivalent impurity(1 marks) 1(a)(v) What is the life time of charge carriers in metastable state? (1 marks) 1(a)(vi) Total internal reflection occurs when a light ray t ravels from ______to_______(1 marks) 1(a)(vii) What is persistent current?(1 marks) 1(b)(i) Give brief account of temperature induced transformation. (3 marks) 1(b)(ii) What is SQUID? Explain with diagram(2 marks) 1(b)(iii) Define X Ray fluoroscopy. Also name its applications. (2 marks) 2(a) Define and explain thermal conductivity. Also deriv e the equation for thermal conductivity K. Write its units. (7 marks) 2(b)(i) Calculate packing fraction for FCC and BCC.(3 marks) 2(b)(ii) In a Hall coefficient experiment a current of 0.25A is sent through ametal strip having thickness 0.2mm and width 5mm.The Hall voltage is found to be 0.15mV, When a magnetic field of 0.2 T is applied. Find: (1) Carrier concentration and (2) Drift velocity of the carrier. (4 marks) 3(a)(i) What do you understand by the term acceptance angle and acceptance cone? Derive an expression for acceptance angle in terms of refractive indices of the core and the cladding. The wavelength of light transmitted through a liquid is 6000A° . The
first order angle of diffraction is 0.046° . Calculate the velocity of ultrasonic waves in the liquid. The frequency of the ultrasonic waves produced by the transducer is 2MHz
(5 marks)
3(a)(ii) How does a laser beam differ from a point source of light? Mention any two engineering applications of laser. (2 marks) 3(b)(i) What is an optical resonator cavity? What role does it play in a laser? (2 marks) 3(b)(ii) What is active medium in Nd:YAG laser and CO2 laser? (3 marks) 4(a)(i) What is an LDR? Explain the working and applications(2 marks) 4(a)(ii) What is zener diode? How zener diode does operates in reverse bias condition(2 marks) 4(b)(i) X rays of unknown wavelength give first order Bragg 's reflection at glancing 20°with (212) planes of copper having FCC structure.Find wavelength of X Rays ,if the lattice constant for copper is 3.615A°(4 marks) 4(b)(ii) A Hall has a volume of 2265m3.Its total absorption is equivalent to94.85m2 of open window. What will be effect on reverberati on time if audience fills the hall and there by increases the absorption by another 94.85m2 (3 marks) 5(a) Discuss magnetic field effect and diamagnetic property of D54superconductor. Prove that ?m= 1 or superconductor. (7 marks) 5(b)(i) Discuss at least three of the engineering applicati ons of ultrasound. (3 marks) 5(b)(ii) Draw circuit diagram of magnetostriction oscillator and explain the working. (4 marks) 6(a)(i) Classify the fibres on the basis of refractive inde x profile, on the basis of modes of propagation and on the basis of materials. (5 marks) 6(a)(ii) What is the numerical aperture of an optical fibre cable with a clad index of 1.378 and a core index of 1.546? (2 marks) 6(b)(i) A uniform silver wire has a resistivity of 1.54x10 8 ohm.metre at room temperature. For an electric field along the w ire of 1volt/cm. Calculate (1)drift velocity ,(2) Mobility, (3)relax ation time of electron assuming that there are 5.8x10 28conduction electron per metre3 of the material. Given Me = 9.1x10 31kg and e = 1.6 x 10 19coulomb(5 marks) 6(b)(ii) Mention any four names of NDT methods.(2 marks) 7(a) What are metallic glasses? How to prepare them? Wri te also the names of other techniques. (7 marks) 7(b)(i) State and explain Weber Fechner law.(3 marks) 7(b)(ii) What are Miller indices? Draw crystal planes having Miller indices (210),(101) and (010) for simple cubic structure (4 marks)

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