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Sample Exam Paper

BAS101Sample Examination Paper — II

Course: Engineering Physics (BAS101)Programme: B.Tech. — Semester I (Common to all branches)
Time: 3 HoursMaximum Marks: 70

General Instructions:

  1. All questions in Section A are compulsory.
  2. Attempt any two parts from each question in Section B.
  3. Attempt any two questions in full from Section C.
  4. Draw neat, labelled diagrams wherever necessary.

Section A — Short Answer (Compulsory)

  1. State the Michelson–Morley experiment's objective and its outcome. (2 marks)
  2. Write the relation between relativistic energy, momentum and rest mass. (2 marks)
  3. What is a wedge-shaped thin film? State the expression for its fringe width. (2 marks)
  4. Define resolving power of a diffraction grating. (2 marks)
  5. What is specific rotation? Name the instrument used to measure it. (2 marks)
  6. Differentiate between spontaneous emission and stimulated emission. (2 marks)
  7. What are step-index and graded-index optical fibres? (2 marks)

Section B — Attempt any two parts of each

  1. Explain the Michelson–Morley experiment and discuss why its null result was significant for relativity. (5 marks)
  2. Derive the expression for the radius of the nth bright ring in Newton's rings by reflected light. (5 marks)
  3. Describe Fraunhofer diffraction due to a double slit and explain the resultant intensity distribution. (5 marks)
  4. Explain the working of a quarter-wave plate and show how it converts plane polarized light into circularly polarized light. (5 marks)
  5. Describe the working of a He-Ne laser with the help of an energy level diagram. (5 marks)

Section C — Attempt any two questions in full

  1. Starting from the postulates of special relativity, derive the Lorentz velocity addition formula, and show that it reduces to the Galilean result for v ≪ c. (10 marks)
  2. Describe the experimental arrangement for the formation of Newton's rings. Explain why the centre of the ring system is dark in the reflected pattern and derive the relevant radius expression. (10 marks)
  3. Derive the condition for principal maxima in a plane diffraction grating and explain, using Rayleigh's criterion, how resolving power depends on the number of lines and the order of the spectrum. (10 marks)
  4. Explain Fresnel's theory of optical activity. Describe the construction and use of a Laurent's half-shade polarimeter to determine the specific rotation of a sugar solution. (10 marks)
  5. Describe the principle of total internal reflection in optical fibres. Derive the expression for numerical aperture and discuss the causes of attenuation and dispersion in fibre-optic communication systems. (10 marks)