BSC 3rd Semester Physics Past Paper 2019 PDF

http://www.rtmnuonline.com NRT/KS/19/2077 Bachelor of Science (B.Sc.) Semester—III Examination PHYSICS (Sound Waves, Applied Acoustic,...

http://www.rtmnuonline.com NRT/KS/19/2077 Bachelor of Science (B.Sc.) Semester—III Examination PHYSICS (Sound Waves, Applied Acoustic, Ultrasonic and Power Supply) Optional Paper—I Time : Three Hours] [Maximum Marks : 50 N.B. :— (1) All questions are compulsory. (2) Draw neat diagrams wherever necessary. EITHER 1. (A) Define progressive wave. Obtain an expression for the speed of transverse wave formed on a stretched string. 5 (B) (i) Define phase velocity and group velocity. Derive the relationship between phase velocity and group velocity. 3 (ii) If the tension applied to stretched string is increased by 20%, what will be the percentage change in its frequency ? 2 OR (C) Show that only odd harmonics are present in a closed organ pipe. 2½ (D) What do you mean by temperament of a musical scale ? Describe equally-tempered scale. 2½ (E) The frequency of fundamental note from a closed organ pipe is 200 Hz. What will be the frequency of fundamental note for an open organ pipe having same length ? 2½ (F) Explain the terms : (i) Pitch (ii) Loudness (iii) Quality of sound. 2½ EITHER 2. (A) State the principle of loudspeaker. Explain the construction and working of moving coil loudspeaker. 5 (B) (i) Explain variable area method of recording of sound on cine film. 3 3 (ii) For an empty hall of size 20×15×10 m , the reverberation time is 3.5 seconds, calculate the average absorption co-efficient of the hall. 2 OR (C) State any five requirements for good acoustics of an auditorium. 2½ (D) Explain Echelon effect. 2½ 3 (E) Calculate the reverberation time, if the assembly hall having volume 5500 m and sound absorption surface of that hall has an area 750 m2. The average absorption co-efficient of hall is 0.5133. 2½ (F) State principle working of microphone. State any four characteristics of good microphone. 2½ EITHER 3. (A) What is direct and converse piezo-electric effect ? Explain the construction, working and measurement of ultrasonic waves from a piezo-electric generator. 5 (B) (i) Explain acoustic grating. 3 (ii) Calculate the natural frequency of vibration of a ferromagnetic rod of length 500 mm by an ultrasonic generator, where density = 8.1 × 103 kg/m3 and Y = 16 × 1010 N/m2 for the material of the given rod. 2 CLS—13367 1 (Contd.) http://www.rtmnuonline.com http://www.rtmnuonline.com OR (C) Determine the thickness of quartz plate to generate fundamental frequency of 539 kHz used in piezo electric generator. Given Y = 77 × 10 9 N/m2 and ρ = 2.65 × 10 3 kg/m3. 2½ (D) State any five applications of ultrasonic waves. 2½ (E) Explain the mechanism of SONAR. 2½ (F) Explain the working of magnetostriction oscillator circuit using transistor. 2½ EITHER 4. (A) Explain the working of Zener diode as a voltage regulator with suitable circuit diagram. Explain load regulation and line regulation. 5 (B) (i) Deduce the mathematical expressions of the following quantities in case of full wave rectifier : (a) Id c (b) Irms (c) Ripple factor. 3 (ii) A half wave rectifier is used to supply 50 V d.c. to a resistive load of 800 Ω. The diode has a resistance of 25 Ω. Calculate the a.c. voltage. 2 OR (C) What are the merits and demerits of full wave rectifier over half wave rectifier ? 2½ (D) Explain the principle and working of L-Section filter circuit. 2½ (E) Differentiate between regulated and unregulated power supply. 2½ (F) Write a short note on IC voltage regulation. 2½ 5. Attempt any TEN : (i) Define the principle of superposition of waves. (ii) Write the equation for stationary wave. (iii) Differentiate between noise and music. (iv) What are active and passive transducers ? (v) Define reverberation time. (vi) What are live and dead rooms ? (vii) What are ultrasonic waves ? (viii) Write any two applications of SONAR. (ix) List any two methods to detect ultrasonic waves. (x) What is depletion region in a pn-junction ? (xi) What is ‘PIV’ of a diode ? (xii) In a half wave rectifier circuit, a.c. power input is 0.76 Watt and d.c. power output is 0.3 Watt. Calculate percentage efficiency. 1×10 CLS—13367 2 NRT/KS/19/2077 http://www.rtmnuonline.com