Hall Ticket No Question Paper Code: AHS008
INSTITUTE OF AERONAUTICAL ENGINEERING
(Autonomous)
B.Tech II Semester End Examinations (Regular) May, 2017
Regulation: IA-R16
MODERN PHYSICS
(Common for AE/CE/ME)
Time: 3 Hours Max Marks: 70
Answer ONE Question from each Unit
All Questions Carry Equal Marks
All parts of the question must be answered in one place only
UNIT I
1. Define coordination number and atomic packing factor. Calculate the atomic packing factor for
SC and BCC structures.
Draw and explain the structure of diamond with a neat sketch and show that atomic packing
factor of diamond is 0.34.
2. DHow do you find Miller indices of a given plane? An X-ray beam of wavelength 0.7 Ao undergoes
minimum order, Bragg reflection from the plane 0 of cubic crystal at glancing angle 350.
Calculate the lattice constant.
Explain the unit cell and bravias lattice with neat figures. Sketch the following plane in a cubic
unit cell 1 2 0 1).
UNIT II
3. State and prove the Braggs law.
Explain the Frenkel defect and Schottky defect with figures.
4. Discuss the Laue equations with figure.
What are the major applications of X-ray techniques in different fields.
UNIT III
5. Explain the construction and working of a semiconductor diode laser.
Explain the two conditions for laser action. A ruby laser omits a pulse of 20ns duration with
average power per pulse being 100 KW. If the numbers of photons in each pulse is 6:98
calculate the wavelength of photons.
6. Explain the working of a pressure sensor with a diagram.
What are active and passive sensors? What are the advantages of optical fiber sensors?
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UNIT IV
7. What is acceptance angle? Obtain an expression for acceptance angle.
Calculate the numerical aperture and acceptance angle for an optical fiber with core and cladding
refractive indices being 1.563 and 1.498 respectively.
8. What is attenuation? Explain the factors contributing to the fibers loss.
Explain the modes of propagation of optical fibers with figure. A fiber with an input power of
9 dBm has a loss of 1.5 db/km. If the fiber is 3000 m long, what is the output power.
UNIT V
9. Obtain the expression for interference due to reflected light in thin films.
what is diffraction of light? A diffraction grating used at normal incidence gives a line (5400 Ao)
in a certain order superposed on the violet line (4000 Ao) of the next higher order. If the angle
of diffraction is 300, how many lines per cm are there in the grating?
10. Distinguish between interference and diffraction. In a Newton's rings experiment, show that the
rings get closer as the order increases.
Calculate the thickness of the air film at 10th dark ring in a Newton's rings system viewed
normally by a reflected light of wavelength 500 nm.The diameter of the 10th dark ring is 2 mm.

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