( PART : B DESCRIPTIVE )

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1 PHY/II/02 (PR) ( 2 ) ( 2nd Semester ) PHYSICS SECOND PAPER ( Oscillations, Acoustics and Optics ) ( Pre-revised ) Full Marks : 55 Time : 2½ hours ( PART : B DESCRIPTIVE ) ( Marks : 35 ) The figures in the margin indicate full marks for the questions 1. Derive the differential equation of simple harmonic motion and hence obtain the solution. 2+5 Or Two simple harmonic motions x A sin ( t ) and y B sin t superposed each other at right angle. Obtain the general equation for the resultant simple harmonic G7/299a ( Turn Over ) motion after they superposed each other and hence discuss the case when (a) 2 ; (b) Write the differential equation for free undamped vibration. Hence obtain the solution. What happens to the amplitude of the vibration? Or Explain the production of ultrasonic wave by piezoelectric method. Write down any three uses of ultrasonic wave Deduce the condition for achromatism of two thin lenses separated by small distance d. 7 (a) Or By the concepts of cardinal points in thick lens, answer the following questions : (i) (ii) How many refractions take place for a single light ray when passing through the lens? In which plane does refraction take place? G7/299a ( Continued )

2 ( 3 ) ( 4 ) (iii) What is the advantage of the concepts of cardinal points over the idea of considering refractions at each surface of the lens? (b) Show that the nodal points and principal points in a thick lens coincide, if the refractive indices are same on either sides of the lens Discuss the basic theory of interference of light. Show that the condition for constructive interference is 2n, where is phase difference between the two light waves. 3+4 (c) (d) What is phase retardation plate? Discuss half-wave plate, mentioning its uses. Or Obtain the expressions for Einstein s A and B coefficients. 7 Or Discuss the theory of Newton s ring. How do you determine the wavelength of light with the help of Newton s ring? Answer the following questions : (a) What do you mean by double refraction? (b) What are O-ray and E-ray in reference to double refraction? G7/299a ( Turn Over ) G7 200/299a PHY/II/02 (PR)

3 Subject Code : PHY/II/02 (PR) Booklet No. A To be filled in by the Candidate Date Stamp DEGREE 2nd Semester (Arts / Science / Commerce / ) Exam., Subject... Paper... INSTRUCTIONS TO CANDIDATES 1. The Booklet No. of this script should be quoted in the answer script meant for descriptive type questions and vice versa. 2. This paper should be ANSWERED FIRST and submitted within 45 minutes of the commencement of the Examination. 3. While answering the questions of this booklet, any cutting, erasing, overwriting or furnishing more than one answer is prohibited. Any rough work, if required, should be done only on the main Answer Book. Instructions given in each question should be followed for answering that question only. To be filled in by the Candidate DEGREE 2nd Semester (Arts / Science / Commerce /... ) Exam., 2017 Roll No.... Regn. No.... Subject... Paper... Descriptive Type Booklet No. B... Signature of Scrutiniser(s) Signature of Examiner(s) Signature of Invigilator(s) /299

4 PHY/II/02 (PR) ( 2nd Semester ) PHYSICS SECOND PAPER ( Oscillations, Acoustics and Optics ) ( Pre-revised ) ( PART : A OBJECTIVE ) ( Marks : 20 ) The figures in the margin indicate full marks for the questions SECTION A ( Marks : 5 ) Tick ( ) the correct answer in the brackets provided : 1 5=5 1. The average kinetic energy of a particle of mass m, executing simple harmonic motion of frequency f, amplitude a, is (a) ma f ( ) (b) ma f ( ) (c) (d) 2 ma 2 f ma 2 f 2 2 ( ) ( ) /299

5 ( 2 ) 2. If b is the damping constant, is the natural frequency of the oscillating system, then the frequency of vibration is (a) 2 2 2b 2 ( ) (b) 2 2 b 2 ( ) (c) 2 2 b 2 ( ) (d) 2 2 2b 2 ( ) 3. The condition for achromatism of two lenses in contact is (a) (b) 1 f 1 1 f ( ) f ( ) f 2 (c) 1 2 f 1f 2 0 ( ) (d) 1f 1 2 f 2 0 ( ) PHY/II/02 (PR)/299

6 ( 3 ) 4. In everyday life, diffraction of sound is observed whereas diffraction of light is not. This is due to the fact that (a) sound is longitudinal in nature ( ) (b) wavelength of sound is very small ( ) (c) light is transverse in nature ( ) (d) wavelength of light is very small ( ) 5. At Brewster s angle, the angle between the reflected light and refracted light is (a) 60 ( ) (b) 120 ( ) (c) 90 ( ) (d) 45 ( ) PHY/II/02 (PR)/299

7 ( 4 ) SECTION B ( Marks : 15 ) Write very short answers to the following questions : 3 5=15 1. The displacement of a particle is given by x x 0 sin t Show that it performs simple harmonic motion. PHY/II/02 (PR)/299

8 ( 5 ) 2. Define the following : Melody ; Harmony ; Intensity of sound. PHY/II/02 (PR)/299

9 ( 6 ) 3. A light is incident on the glass surface. The reflected light becomes plane polarized. Calculate the polarizing angle and the angle of refraction. [Given refractive index of glass = 1 54, tan 1 (1 54) = 57 ] PHY/II/02 (PR)/299

10 ( 7 ) 4. Give the differences between Fresnel diffraction and Fraunhofer diffraction. PHY/II/02 (PR)/299

11 ( 8 ) 5. What is polarization of light? Why is only electric field considered, not the magnetic field of light in case of polarization? G7 200/299 PHY/II/02 (PR)

12 PHY/II/02 (R) ( 2 ) ( 2nd Semester ) PHYSICS SECOND PAPER ( Oscillations, Acoustics and Optics ) ( Revised ) Full Marks : 55 Time : 2½ hours ( PART : B DESCRIPTIVE ) ( Marks : 35 ) The figures in the margin indicate full marks for the questions 1. (a) Show that the total energy of a particle in simple harmonic motion is conserved. 3 (b) Derive an expression for the time period of oscillation of a compound pendulum. 4 Or What do you mean by standing waves? How are nodes and antinodes formed? Find an expression for normal modes of a standing wave. 7 G7/298a ( Turn Over ) 2. Obtain the amplitude of vibration of a system vibrating under the influence of an external vibrating agency. When does resonance occur? Explain the term sharpness of resonance and mention the factors on which it depends. Or Obtain the expression for the growth of energy density in an enclosure (room) of volume V (a) Using the concepts of cardinal points in thick lens, answer the following questions : (b) (i) (ii) How many refractions take place for a single-light ray when passing through the lens? In which plane does refraction take place? (iii) What is the advantage of the concepts of cardinal points over the idea of considering refraction at each surface of the lens? 1+1+1=3 Show that in thick lens, nodal points and principal points coincide if the refractive indices are same on either side of the lens. 4 G7/298a ( Continued ) 7

13 ( 3 ) Or What are aplanatic points and aplanatic surface? Discuss the principle of Abbe s homogeneous oil-immersion microscopic objective. 2+5=7 4. Discuss the basic theory of interference of light. Show that the condition for constructive interference 2 n, where is phase difference between the two light waves. 3+4=7 Or Discuss the theory of Newton s ring. On what phenomenon does it depend? How can the wavelength of light be determined with the help of Newton s ring? 2+1+4=7 5. What is zone plate? Give the theory of zone plate. Show that a zone plate has multiple foci =7 Or (a) Explain diffraction at N slits. 2 (b) Give the theory of plane transmission grating and show how you would use it to determine the wavelength of light. 2+3=5 G7 250/298a PHY/II/02 (R)

14 Subject Code : PHY/II/02 (R) Booklet No. A To be filled in by the Candidate Date Stamp DEGREE 2nd Semester (Arts / Science / Commerce / ) Exam., Subject... Paper... INSTRUCTIONS TO CANDIDATES 1. The Booklet No. of this script should be quoted in the answer script meant for descriptive type questions and vice versa. 2. This paper should be ANSWERED FIRST and submitted within 45 minutes of the commencement of the Examination. 3. While answering the questions of this booklet, any cutting, erasing, overwriting or furnishing more than one answer is prohibited. Any rough work, if required, should be done only on the main Answer Book. Instructions given in each question should be followed for answering that question only. To be filled in by the Candidate DEGREE 2nd Semester (Arts / Science / Commerce /... ) Exam., 2017 Roll No.... Regn. No.... Subject... Paper... Descriptive Type Booklet No. B... Signature of Scrutiniser(s) Signature of Examiner(s) Signature of Invigilator(s) /298

15 PHY/II/02 (R) ( 2nd Semester ) PHYSICS SECOND PAPER ( Oscillations, Acoustics and Optics ) ( Revised ) ( PART : A OBJECTIVE ) ( Marks : 20 ) The figures in the margin indicate full marks for the questions SECTION I ( Marks : 5 ) Tick ( ) the correct answer in the brackets provided : 1 5=5 1. Chladni s figures are vibration patterns formed in (a) vibrating strings ( ) (b) vibrating membranes ( ) (c) vibrating plates ( ) (d) vibrating liquid surface ( ) /298

16 ( 2 ) 2. In forced vibrations, the quantity which measures sharpness of resonance is the (a) amplitude ( ) (b) energy ( ) (c) quality factor ( ) (d) power of vibrating system ( ) 3. A system of two thin convex lenses of focal lengths f 1 and f 2 are separated by a distance d, will behave as a (a) convergent lens ( ) (b) divergent lens ( ) (c) plate ( ) (d) All of the above ( ) PHY/II/02 (R)/298

17 ( 3 ) 4. For two sources to be coherent, it is essential that they must be (a) monochromatic ( ) (b) multichromatic ( ) (c) independent ( ) (d) derived from same source and must be monochromatic ( ) 5. If N is the number of rulings in the grating, n is the order of spectrum and is the wavelength of light used, the resolving power of grating is d (a) Nn ( ) (b) Nn ( ) (c) (d) N n Nd d ( ) ( ) PHY/II/02 (R)/298

18 ( 4 ) SECTION II ( Marks : 15 ) Write very short answers to the following questions : 3 5=15 1. Explain Chladni s figures. PHY/II/02 (R)/298

19 ( 5 ) 2. Explain what happens when a pulse of ultrasonic wave is impressed upon a piezoelectric crystal. PHY/II/02 (R)/298

20 ( 6 ) 3. Mention three points of distinction between Huygens eyepiece and Ramsden eyepiece. PHY/II/02 (R)/298

21 ( 7 ) 4. State and explain Brewster s law for polarization of light. PHY/II/02 (R)/298

22 ( 8 ) 5. Explain the difference between Fresnel diffraction and Fraunhofer diffraction. G7 250/298 PHY/II/02 (R)

( PART : B DESCRIPTIVE )

PSY/II/02 (PR) ( 2 ) 2 0 1 7 ( 2nd Semester ) PSYCHOLOGY SECOND PAPER ( Basic Psychology II ) ( Pre-Revised ) Full Marks : 55 Time : 2½ hours ( PART : B DESCRIPTIVE ) ( Marks : 35 ) The figures in the