UPTU Old Question Papers
B Tech 8th Semester
Optical Instrumentation 2007
Notes : (1) Attempt all questions.
(2) All questions carry equal marks.
(3) In case of numerical problem assume data wherever not provided.
(4) Be precise in your answers.
1. Attempt any four parts of the following :
(a) What are the process that are responsible for the emission of light from a source.
(b) What do you mean by quantum numbers ? How, on the basis of quantum numbers energy state of an electron in an atom is defined ?
(c) What are the various electrical and optical characteristics of LED ? Explain any one characteristic.
(d) What is the phenomenon of total internal reflection ? What is the importance of this phenomenon in optical fibers ? What is the phath change a light wave undergoes due to reflection at the interface of the two media :
(i) When it is travelling from rarer to denser medium and
(ii) When it is travelling from denser to rarer medium.
(e) What do you mean by dispersive medium ? Explain why, in a dispersive medium sprading of light pulse occurs ?
(f) Consider the superposition of two waves which are coherent. Show that resultant intensity due to them is not just the sum of their individual intensity.
2. Attempt any four parts from the following :
(a) What is a photodetector ? Explain the classification of a photodetector based on intrinsic and extrinsic process.
(b) Explain, PIN Diode is a more sensitive device than a photoconductor.
(c) What do you mean by injection efficiency of light emitting diode (LED) ? Explain.
(d) What do you understand by coherent detection ? Where this type of detection is important ? Explain with schematic diagram working of a coherent detection system.
(e) Differentiate, white light and monochromatic light. Which source is considered as a monochromatic source in terms of its spectral width ? How spectral width and coherence length of a source an related ?
(f) Why flatness testing is important ? What do you mean by flatness ofWhere the countour testing is required ?
3. Attempt any two parts of the followings :
(a) What do you meant by term ‘LASER’ ? Describe the basic requirement for lasing. How they are achieved in a semiconductor laser ?
(b) Determine the ratio of spontaneous emission transition to the stimulated emission transition under thermal equilibrium.
(c) Explain, how ‘LASER’ is used to measure distance and velocity, Give, experimental technique for the same.
4. Attempt any two parts of the following :
(a) Classify and explain the various type of holograms.
(b) Explain an experimental technique to construct and reconstruct a hologram.
(c) Describe various application of holography.
5. Attempt any two parts of the followings :
(a) What is an optical fiber ? What do you meant
by step index and graded index fiber ? Give an schematic of light propagation in both the types of optical fiber. Give one importance of graded index fiber over the step index fiber.
(b) What are the various mechanisms which limits the information carrying capacity of an optical fiber ? What are the various wavelength windows of a fiber optic communication systems ? Write the advantages of optical fiber over other means of communication medium.
(c) Write a note on erasable optical discs.