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Sample Exam Paper

BAS151Sample Practical Examination — I

Course: Physics Lab (Engineering Physics Laboratory) (BAS151)Programme: B.Tech. — Semester I (Common to all branches)
Time: 3 HoursMaximum Marks: 50

General Instructions:

  1. The examiner will allot one experiment from Group A and one from Group B.
  2. Marks are distributed as: Aim/Theory 5, Procedure & Observations 15, Calculation & Result 15, Viva-voce 15.
  3. Maintain the observation table directly in ink; no rough sheets are allowed for final readings.
  4. Handle glass optical components and mercury/sodium lamps with care.

Section A — Short Answer (Compulsory)

  1. What is the least count of the travelling microscope you are using? (2 marks)
  2. Why must the light source be monochromatic in the Newton's rings experiment? (2 marks)
  3. Why is the centre of the Newton's rings pattern dark in the reflected system? (2 marks)
  4. What is the physical significance of the Hall coefficient? (2 marks)
  5. State Stefan's law and define the Stefan constant. (2 marks)
  6. What precautions are taken while using a ballistic galvanometer? (2 marks)
  7. Define numerical aperture. Why is it important in fibre-optic communication? (2 marks)

Section B — Attempt any two parts of each

  1. Perform the Newton's rings experiment: measure the diameters of at least six dark rings and determine the wavelength of the sodium light used. (5 marks)
  2. Perform the Carey Foster's bridge experiment to determine the specific resistance of the given wire. (5 marks)
  3. Perform the Hall effect experiment on the given semiconductor sample and calculate the Hall coefficient, carrier density and mobility. (5 marks)
  4. Determine the coefficient of viscosity of the given liquid using the terminal velocity (Stokes') method. (5 marks)

Section C — Attempt any two questions in full

  1. Derive the expression for the radius of the nth dark ring in the Newton's rings experiment and explain how you would use your data to find the wavelength of light or the radius of curvature of the lens. (10 marks)
  2. Explain, with a labelled circuit diagram, the working of Carey Foster's bridge and derive the formula used for computing the unknown resistance/resistivity. (10 marks)
  3. Describe the theory of the Hall effect. Derive the expressions used to compute the Hall coefficient, carrier concentration and mobility from your observations. (10 marks)