BANNARI AMMAN INSTITUTE OF TECHNOLOGY SATHYAMANGALAM DEPARTMENT OF PHYSICAL SCIENCES. UNIT II Applied Optics

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$Diffraction c) polarisation d) Transmittance A2 The distance between two successive crests or troughs is called a) amplitude b) Frequency c) wavelength d) time period A3 In longitudinal waves the$

1 BANNAI AMMAN INSTITTE OF TECHNOLOGY SATHYAMANGALAM DEPATMENT OF PHYSICAL SCIENCES NIT II Applied Optics PAT A A1 The superimposition of one light wave over another is called as a) interference b) Diffraction c) polarisation d) Transmittance A2 The distance between two successive crests or troughs is called a) amplitude b) Frequency c) wavelength d) time period A3 In longitudinal waves the particles vibrates to the direction of propagation a) parallel b) in the opposite direction c) at right angles d) inclined at 45 o A4 For constructive interference, the path difference between two interfering waves is a) n λ/2 b) (2n 1) λ c) n λ d) (2n 1) λ/2 A5 For destructive interference, the path difference between two interfering waves is a) n λ/2 b) (2n 1) λ/2 c) n λ d) (2n 1) λ A6 In air-wedge film experiment, the flatness of a surface is determined using the pattern a) diffraction b) interference c) polarisation d) none of the above A7 The process in which an atom goes to the excited state with the help of external energy is a) stimulated emission b) stimulated absorption c) spontaneous emission d) spontaneous absorption A8 The transition mechanism which is more important for the operation of LASE is a) spontaneous absorption b) spontaneous emission c) stimulated absorption d) stimulated emission A9 Which event is likely to take place when a photon of energy equal to the difference in energy between two levels is incident in a system? a) absorption b) Emission Page 1 of 7

2 c) absorption and emission d) Polarization A10 Coherence in lasers is due to a) spontaneous emission b) stimulated emission c) population inversion d) thermal equilibrium A11 If the two light waves are said to be coherent, they have a) same wavelength, same amplitude and different phase difference b) same wavelength, different amplitude and constant phase difference c) different wavelength, same amplitude, different phase difference d) same wavelength, same amplitude and constant phase difference A12 Light from mercury lamp is a) Monochromatic b) stimulated emission c) highly intense d) spontaneous emission A13 example for molecular gas laser is a) GaAs laser b) ruby laser c) CO2 laser d) Nd:YAG laser A14 CO2 laser was first designed by a) T Maiman b) H M Patel c) C H Townes d) A L Schawlow A15 The LASE which is commonly used in industries for precise cutting of any material is a) CO2 laser b) ruby laser c) dye laser d) semiconductor laser A16 The LASE which is commonly used for optical fiber communication is a) He-Ne laser b) CO2 laser c) semiconductor laser d) Ar laser A17 Which one of the following is not a semiconductor laser? a) GaAs laser b) InP laser c) GaAlAs d) Nd:YAG laser A18 Which one of the following semiconductors can t be used for making laser diode? a) GaAs b) InP c) InGaAsP d) Si A19 There are fundamental modes of vibrations in CO2 molecule a) two b) four c) Three d) five A20 To create laser action we need at least Page 2 of 7

3 a) three levels b) one level c) two level d) fermi energy level A21 The optical phenomena involved in optical fiber communication a) polarisation b) total internal reflection c) transmittance d) refraction A22 Which one of the following is the mathematical expression for Snell s law a) sin ф1 = (n2/n1) sin ф2 b) sin ф1 = (n1/n2) sin ф2 c) sin ф1 = (n2 n1) sin ф2 d) sin ф1 = (n2 + n1) sin ф2 A23 The condition to obtain total internal reflection is (where n1 and n2 are refractive indices of core and cladding, respectively) a) n1 > n2 b) n1+n2 = 0 c) n2 > n1 d) n1 = 0 A24 Acceptance angle of the fiber is expressed as a) sin Φmax = (n1 n2) b) sin Φmax = (n1 n2) 1/2 c) sin Φmax = (n1 + n2) 1/2 d) sin Φmax = n1 2 n2 2 A25 The refractive index of a material is given by the relation () a) c 2 /ν b) c ν c) c/ν 2 d) c / ν A26 In optical fiber, the light should travel from () a) rarer to denser b) from outer layer to core c) from cladding to core d) denser to rarer A27 Optical fiber is generally made up of a) alloys b) ubber c) metal d) Silica A28 Optical fibers are a) Conductive b) Non-conductive c) Semiconductive d) Absorptive A29 The relative refractive index fiber is and the refractive index of core is Its N.A. is a) b) c) 30.3 d) 303 A30 In the optical fiber, if the refractive index of core is maximum along the fiber axis and if it gradually decreases with radial distance, then it is called a) step index fiber b) single mode fiber c) graded index fiber d) multi-mode fiber Page 3 of 7

4 A31 In the step index fiber, the light ray propagation is in the form of rays a) skew b) meridional c) straight d) indirect A32 To increase the numerical aperture of a fiber, we should a) increase the difference between core b) increase the length of the fiber and cladding refractive indices c) decrease the refractive index difference d) decrease the diameter of the fiber between core and cladding A33 Which one of the following is not true for the case of silica fibers a) SiO2 is transparent for V and I rays b) good chemical stability c) high creep resistance d) high thermal expansion B1 Define interference. PAT B B2 B3 B4 B5 B6 B7 B8 B9 Can we form air wedge using two glass plates? Justify. List two applications of air wedge. A wedge-shaped air film is formed between two glass plates by placing a wire at one of the sides. On illuminating this film by a light of 6000 Å wavelength, 10 fringes are seen in one centimeter. If the light is incident normally, find the angle of the wedge. Identify the role of population inversion in lasers. Illustrate the role of nitrogen and helium in CO2 laser Indicate the role of optical resonators in the production of laser Distinguish between spontaneous and stimulated emission Differentiate ordinary light and laser light B10 List four properties of Laser beam B11 Name four applications of laser in engineering and industry field B12 Mention the principle of semiconductor laser B13 List the conditions for total internal reflection B14 ecall the advantages of optical fibers in communication over other communication systems B15 Define numerical aperture Page 4 of 7

5 B16 Distinguish single mode and multimode fiber B17 Classify the optical fibers based on mode, refractive index and materials. B18 Illustrate the role of cladding in an optical fiber B19 Name four applications of fiber optic cables B20 A silica optical fiber has a core refractive index of 1.50 and a cladding refractive index of Determine the numerical aperture for the fiber. PAT C Qn. No. Sub Division Questions Marks C1 Derive an expression for the thickness of a thin material using interference phenomenon in an air wedge C2 i Explain the identification of the flatness of the surface and thickness of thin material from the interference pattern. ii A thin wire used in an air-wedge experiment produces straight line parallel fringes having a mean fringe width of 1.5 mm with sodium light of nm wavelength. If the length of the air wedge is 45 mm, find the thickness of the wire used. C3 i Explain the principle, construction and working of a molecular gas laser with neat energy level diagram ii List four applications of CO2 laser 4 C4 i Discuss the construction and working of a semiconductor laser 8 ii Indicate the merits and demerits of semiconductor laser 4 C5 i Differentiate step index and graded index optical fiber 8 ii Draw the block diagram of optical fiber communication system 4 C6 Find the expression for the acceptance angle, numerical aperture and deduce the relation between fractional index and numerical aperture 12 Page 5 of 7

6 The Knowledge Dimension The Cognitive Process Dimension emember nderstand Apply alyze Evaluate Create Factual Knowledge A10, A14, A19, A27, A28, A31, B12, B15, A1, A2, A13, A22, Page 6 of 7

7 Conceptual Knowledge A2, A7, A15, A16, B1, B3, B10, B13, B14, B17, B19, A4, A5, A8, A11, A20, A21, A23, A24, A25, A26, A30, A32, B5, B11, C2(i), C3(ii), C4(ii) B4, B20, C1, C2(ii) A3, A9, A17, A18, A29, A33, B2, B8, B9, B16, C5(i), Procedural knowledge A6, B6, B7, B18, C3(i), C4(i), C5(ii), C6 Meta-cognitive knowledge Page 7 of 7

DRONACHARYA COLLEGE OF ENEGINEERING DEPARTMENT OF APPLIED SCEINCE AND HUMANITIES SHORT ANSWER QUESTIONS: Unit-I. Chapter I: Interference

DRONACHARYA COLLEGE OF ENEGINEERING DEPARTMENT OF APPLIED SCEINCE AND HUMANITIES SUBJECT: PHYSICS-I CODE: PHY-101-F SHORT ANSWER QUESTIONS: Unit-I Chapter I: Interference 1. State the condition for sustained