JNTU
JNTU B.Tech I ENGINEERING PHYSICS Previous Question Paper (December - 2018 - R16)
Part A is compulsory which carries 25 marks. Answer all questions in Part A. Part B consists of 5 Units. Answer any one full question from each unit. Each question carries 10 marks.
Part A
Explain the concept of coherence.
Answer
Coherence is the property of light waves that maintain a constant phase relationship over time and space. It is classified into temporal coherence, which relates to the monochromaticity of the source, and spatial coherence, which relates to the phase correlation at different points across the wavefront.
Find the resolving power of grating having 5000 lines/cm in the first order diffraction. The length of the grating is 16cm.
Answer
The resolving power of a grating is given by R = nN, where n is the order of diffraction and N is the total number of lines on the grating. Given n = 1 and the grating density is 5000 lines/cm over a length of 16 cm, the total number of lines N = 5000 lines/cm × 16 cm = 80,000. Thus, the resolving power R = 1 × 80,000 = 80,000.
Distinguish between quarter wave plate and half wave plate.
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Write short notes on Malu’s law.
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Explain the terms numerical aperture and acceptance angle.
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Write the classification of optical fibres.
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Mention seven crystal systems.
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Explain the terms i) basis, ii) Space lattice, iii) Bravice lattice.
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Write the Bragg’s law and explain the terms.
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Explain stacking faults, twin tilt and grain boundaries.
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Part B
Explain the formation of Newton’s rings.
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Obtain the expression for nth bright fringe and nth dark fringe in Newton’s rings by reflected light.
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Explain Fraunhofer diffraction.
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Explain the determination of wavelength of light using grating.
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Explain the theory of He-Ne laser.
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With neat diagram write the working of He-Ne laser.
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Write the important elements in Ruby laser and explain its working.
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Discuss population inversion and optical activity.
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Describe the construction of optical fibre.
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Distinguish between light propagation in step index fibre and graded index fibre.
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Discuss different types of optical fibres.
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Discuss the applications of optical fibres in sensors.
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What are Miller indices and how they are obtained.
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Draw (111) and (110) planes in a cubic lattice.
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Describe crystal structure of ZnS.
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Obtain packing factor for FCC and BCC structures.
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Explain different point defects.
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With neat diagram explain powder method in crystal structure determination.
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Write the elements present in Laue method and their functioning.
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Distinguish between edge and screw dislocation.
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What is Burger’s vector.
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