JAWAHARLAL NEHRU TECHNOLOGICAL UNIVERSITY HYDERABAD
JAWAHARLAL NEHRU TECHNOLOGICAL UNIVERSITY HYDERABAD B.Tech I Year ENGINEERING PHYSICS - I Previous Question Paper (March/April - 2023 - R16)
Question paper consists of Part A, Part B. Part A is compulsory, which carries 25 marks. In Part A, Answer all questions. In Part B, Answer any one question from each unit. Each question carries 10 marks and may have a, b as sub questions.
Part A
An observer through mesh is observing a diffraction pattern in his room due to street light, which type of diffraction is this, explain?
Answer
This is an example of Fraunhofer diffraction. In this scenario, the street light acts as a source at an effectively infinite distance from the mesh, and the observer's eye (or a lens) focuses the parallel rays of light diffracted by the mesh onto the retina, which acts as a screen. Since both the source and the screen are at an infinite distance relative to the diffracting aperture, it satisfies the conditions for Fraunhofer diffraction.
Write uses of interference of light.
Answer
Interference of light is a fundamental phenomenon with several practical applications in engineering and metrology:
- Optical Testing: It is used to test the flatness and surface quality of optical components like lenses and prisms by observing interference fringes formed between the surface and a reference flat.
- Thin Film Measurement: The thickness of extremely thin films or coatings can be precisely measured by analyzing the interference patterns produced by reflected light.
- Interferometry: Instruments like the Michelson interferometer utilize interference to measure wavelengths of monochromatic light, determine the refractive index of transparent materials, and detect minute displacements or changes in path length with high precision.
Calculate the thickness of a quarter wave plate for μe= 1.533 and μo= 1.544, λ = 5000 A.
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Define the stimulated emission and mention its characteristics.
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Classify the optical fibers based on the refractive index of core.
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The fractional refractive index of an optical fiber 0.0004 and clad refractive index is 1.48. Calculate numerical aperture of the fiber.
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Draw the planes (101) and (100) in a cubic unit cell of unit dimensions.
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Obtain the relation between atomic radius ‘r’ and unit cell edge ‘a’ for BCC.
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Classify the defects in solids.
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Write note on grain boundaries.
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Part B
Derive the condition for maxima and minima of interference when a beam of light incident obliquely on a thin transparent parallel film.
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A parallel beam of light 5890 A sticks a film of oil (μ = 1.46) floating on water (μ= 1.33), when viewed at an angle 300 from the normal, eight dark bands are seen. Find the thickness of the film.
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Define diffraction grating and discuss the Fraunhofer diffraction at N-slits.
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A parallel beam of light is allowed to incident normally on a plane grating having 4250 lines/cm and second order is observed at 300. Find the wavelength of the incident light.
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Define double refraction and discuss how polarized light is obtained with Nicol prism.
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State and explain the Mauls’s law.
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Describe the working of semiconductor laser.
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Write the characteristics of laser light.
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Define acceptance angle of an optical fiber and derive expression for it.
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Discuss the advantages of optical fibers as a vehicle of communication over the conventional medium.
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Explain the different sources of attenuation in optical fibers and how these can be measured.
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Write a note on sensor applications of optical fibers.
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Calculate the atomic packing fraction for SC and FCC.
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Define Miller indices and mention its features.
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Deduce an expression for inter planar spacing of crystal planes.
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Calculate the atomic packing fraction for diamond.
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Explain the Laue method for X-ray diffraction.
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Write note on Edge and screw dislocation.
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Define and explain in detail Schottky and Frenkel defects.
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Mention the advantages and disadvantages of defects in solids.
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