Anna University 1st Semester PHYSICS

Question Bank – CAT-I

Unit 1 ULTRASONICS

Part – A

1. Mention any 4 properties of ultrasonic waves.
2. What is magnetostriction effect?
3. What is meant by piezoelectric effect?
4. What are the different methods used for the production of ultrasonic waves?
5. What is SONAR? Explain how ultrasonic waves are used in SONAR.
6. What is meant by Sonogram?
7. What is acoustic grating?
8. Name any four methods of detection of ultrasonic waves.
9. What are the different scanning methods used in ultrasonic?
10. How are ultrasonic waves used to measure depth of sea?
11. What is cavitation? Mention its use.
12. Explain the application of ultrasound in medical field.
13. An ultrasonic source of 0.07 MHz sends down a pulse towards the seabed which returns after 0.65 sec. The velocity of sound in sea water is 1700 m/s. Calculate the depth of the sea.

Part – B

1. Explain with neat circuit diagram, the generation of ultrasonic waves using magnetostriction method and list out some properties of ultrasonic waves.(12+4)

2. (i) Explain how ultrasonic waves can be produced by using piezoelectric crystal and write any four  

     applications of ultrasonic. (12)

             (ii) A ultrasonic generator consists of a quartz plate of thickness 0.7 mm and density 2800 kg/m³. Find the   

                   fundamental frequency of ultrasonic waves if the Young’s modulus of quartz is 8.8 x 10 ¹⁰ N/m².(4)

3. Describe the following:

(i)                   Discuss about the application of ultrasonic waves in NDT. (8)

(ii)                 Different modes of scanning used in ultrasonic Imaging technique. (8)

4. (i) What is acoustic Grating? With a neat diagram explain the theory and use of it to determine the velocity      

      of ultrasonic waves in liquid. (2+8)

(ii)  Industrial application of ultrasonics (6)

UNIT 2   LASER AND ITS APPLICATION

Part – A

1.        What does the term LASER stands for?

2.        What are the characteristics of laser beam?

3.        What is mean by coherence in laser light?

4.        Distinguish between spontaneous and stimulated emission.

5.        What are Einstein’s coefficients A and B in laser?

6.        What is the principle of laser?

7.        What are the conditions needed for the laser action?

8.        What is meant by population inversion and metastable state.?

9.        What is meant by pumping mechanism?

10.     What are different types of pumping mechanism to achieve population inversion?

11.     What are the important requisites for laser action to takes place?

12.     What are the different types of laser?                                                                                          

13.     What is meant by direct band gap and indirect band gap semiconductor?

14.     What are the roles played by the He and N₂ in CO₂  laser?

15.     Mention any two applications of laser.

16.     What is meant by hologram?

17.     What is the reason for using a laser beam in holography?

18.     State any four applications of laser in engineering and industry.

19.     State any four application of laser in medicine.

20.     How will you convert LED into laser source?

21.     Compare holography with photography.

22.     Write down the ratio of the stimulated emission to spontaneous emission.

23.      What is the principle of semiconductor laser?

24.     What are the advantages of heterojunction semiconductor laser over homojunction  semiconductor laser?

Part – B

1.        For atomic transitions, derive Einstein relation and hence deduce the expressions for the ratio of spontaneous emission rate to the stimulated emission rate. (16)

2.        Explain the different methods used for pumping of atoms.(8)

3.        What is a gas laser? Explain the working of He-Ne laser with relevant diagram.(8)

4.        Describe the construction and working of Nd-YAG laser.(8)

5.       What is a molecular gas laser? Explain the modes of vibrations of CO₂ molecule and describe the construction and working of a CO₂ laser with a neat sketch. (16)

6.        What is a semiconductor diode laser? Explain the construction and working of Ga-As laser. (homojunction semiconductor laser)(8)                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                   

7.       Explain with a neat sketch the construction and reconstruction of a hologram using laser beam.(8)

8.        Write a short notes on material processing?(8)

Department of Physics

Question Bank - Unit 3 -FIBRE OPTICS

Part – A

1.      What is fiber optics?

2.      Define acceptance angle and numerical aperture.

3.      What are the types of optical fibers?

4.      Differentiate single mode from multimode fiber.

5.      Define total internal reflection and what are the conditions to obtain total internal reflection?

6.      Mention the components involved in fiber optical communication system.

7.      What are the advantages of the fiber optical communication system over conventional system?

8.      Why optical fibers are called as waveguides?

9.      What are the differences between step index and graded index fiber?

10.  What type of sources is used for optical communication system?

11.  What is called mode of propagation in optical fibres?

12.  Define intermodal dispersion.

13.  Define attenuation in an optical fibre and mention its unit.

14.  What is dispersion?

15. Calculate the Numerical aperture and Acceptance angle of a fibre with the core refractive index of 1.54 and cladding 1.50.
16. A silica optical fiber has a core refractive index of 1.5 and cladding refractive index of 1.47. Calculate the Critical angle at the core-cladding interface.
17. A signal of 100mW is injected into a fibre. The outgoing signal from the other end is 40mW. Find the loss in dB.
18. What is splicing? Mention the two types of splicing.
19. List any four factors that cause losses in optical fibre.

20.  What are active and passive sensors?

Part – B

1. (i) Define Numerical aperture and derive an expression for the Numerical aperture and Acceptance angle of fibre in terms of refractive index of the core and cladding of the fibre. (8)

(ii) Describe the double crucible technique for the production of optical fibre cables (8)

      2.   (i) Discuss the mechanisms of attenuation, dispersion and bending losses in optical fibres.(10)

(ii) Explain the principles and working of temperature and displacement sensors with neat   

      diagram. (6)

3. (i) Explain the various types of optical fibres (10)

       (ii) Describe the construction and working of an Endoscope (6)

4.  Explain in detail about light sources and light detectors involved in optical fibre communication with necessary diagram. (16)

5.       (i) Describe a fiber optic communication system with block diagram.

 (ii) Describe the principle, construction and working of light emitting diode.

 (iii) Give the advantages of fibre optic communication over conventional system. (6+8+2)

Unit 4 Quantum Physics

Part – A

1. What is the physical significance of wave function?
2. Give the special features of Quantum theory of radiation.
3. What is the principle of electron microscope?
4. Explain the principle of transmission electron microscope
5. Calculate the de-broglie wavelength of an electron, which has been accelerated from rest on application of potential of 400V
6. Deduce Rayleigh-Jeans law from Planck’s law for radiation.
7. The wavelength of X-ray photon is doubled when it is scattered through an angle of 90⁰ by a target material. Find the incident wavelength.
8. The de-broglie wavelength of an electron is 1.226A⁰. What is the accelerating potential?
9. What is Compton wavelength and calculate its value.
10. What are degenerate and non degenerate states?

Part – B

1.       What are the basic postulates of quantum theory of light? Derive Planck’s law of radiation. (4+12)

2.       Derive time dependent Schrodinger wave equation and hence derive time independent Schrodinger wave equation. (16)

3.       Give the theory of Compton Effect and briefly explain its experimental verification. (16)

4.        (i) Derive time-independent Schrodinger wave equation. (6)

(ii)Using time-independent Schrodinger wave equation normalize the wave function of electron trapped in a One-dimensional potential well. (10)

5.       Compare SEM and TEM.(6)

6.       An X ray photon of wavelength 1.24 x 10^-3A⁰ is scattered by a free electron through an angle 90⁰. Calculate the energy of the scattered photon(4)

7.       With a neat sketch, describe the scanning process of a SEM.

Unit 5   Crystal Physics

Part – A

1.        Define space lattice.

2.        What is meant by basis?

3.        Define the term crystal structure.

4.        What are interfacial angles?

5.        Define the term unit cell.

6.        What is meant by lattice parameters?

7.        Name the seven types of crystal systems.

8.        What is Bravais lattice?

9.        What are miller indices?

10.     Draw the crystal planes for (110) and (001).

11.     Define the following term (i) Atomic radius  (ii) Co ordination number  (iii) packing density

12.     Show that for a BCC crystal structure, the lattice constant is given by , where r is the atomic radius.

13.     Establish the relationship between the radius and the inter atomic distance for a FCC crystal.

14.     Draw a diagram of the unit cell of the closed HCP.

15.     For a cubic lattice, draw the (231) plane showing the value of intercepts with the coordinate axes.

16.     Draw the schematic diagram of SC, BCC and FCC unit cells.

17.     What is a primitive unit cell?

18.     Show that for a simple cubic system d₁₀₀:d₁₁₀:d₁₁₁: : 6:3:2

19.     The lattice constant for a unit cell is 2.02Å. Calculate the spacing of (111) plane.

20.     The lattice constant for a FCC structure is 4.938A⁰. Calculate the interplanar spacing of (220) planes.

21.     The lattice constant of a metal with cubic lattice is 2.88 A⁰. The density of metal is 7200 Kg/m³. Calculate the number of unit cell present in 1Kg of the metal.

22.     Determine the lattice constant for FCC crystal having atomic radius 1.476A⁰.

23.     Which crystal structure is having least coordination number? Give example.

24.     Give the relationship between interplanar distance and cubic edges.

25.     What is polymorphism and allotropy?

26.     Give an account on imperfections in crystal.

27.     Write a note on point imperfections.

28.     What are Vacancies?

29.     Write a note on grain boundaries.

30.     Write a short note on Burger vector?

31.     What are dislocations?

32.     What are Frenkel and Schottky imperfections?

Part – B

1.        What are miller indices? How will you determine the miller indices of a given plane? What are the distinct features of miller indices?

2.        Define the term coordination number, atomic radius and packing density. Calculate the above factors for SC, BCC and FCC.

3.        Determine the coordination number and packing density for HCP structure. Show that a HCP structure demands an axial ratio of 1.633.

4.        Explain in detail the crystal defects and their types (16)

5.        Explain the characteristics of unit cell of the diamond and NaCl structure.(8)

6.        What is packing factor? Obtain packing factors for SC, BCC and FCC structures. (16)

7.         What are miller indices? Derive an expression for interplanar spacing for (hkl) planes of a cubic structure. (4+8)

8.        Calculate the lattice constant and distance between two adjacent atoms for potassium bromide crystal (FCC lattice) having the density and molecular weight of 2700 Kg/m³ and 119 resp.(6)

9.        Show that the face centered cubic and hexagonal close packed structure has the same atomic packing factor. (10)

10.     Show that for the cubic structure the interplanar distance d in terms of miller indices and cell edge a is given by          (8)

11.       (i) What are Bravais lattice?

           (ii) Derive an expression for the interplanar spacing in a cubic structure.

            (iii) With a neat diagram describe the edge dislocation. (2+8+6)

        

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