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Engineering Physics* Question Paper - May 18 - First Year Engineering (Semester 1) - Pune University (PU)
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Engineering Physics* - May 18
First Year Engineering (Semester 1)
Total marks: 80
Total time: 3 Hours
INSTRUCTIONS
(1) Neat diagram must be drawn wherever necessary.
(2) Figure to the right indicate full marks.
(3) Use of logarithmic table, slide rule, mollier charts, Electronics Calculator, and
steam table is allowed.
(4) Assume suitable data, if necessary.
1.a.
How are Newton’s Rings experimentally obtained? Derive an expression
for the diameter of bright rings in reflected system and show that it is
proportional to the square root of an odd natural number.
(6 marks)
00
1.b.
Find the half angular width of the central maxima in the Fraunhofer
diffraction pattern due to a single slit having a width of $7.07 \times 10^{-5} cm$,
when illuminated by light having wavelength 5000 AU.
(3 marks)
00
1.c.
Find the echo time of ultrasonic's pulse which is travelling with the velocity
$3.1 \times 10^{3} m/s$ in mild steel. The correct thickness measured by Gauss
meter is 9 mm.
(3 marks)
00
OR
2.a.
What is reverberation? Give Sabine’s formula for reverberation time. What
are the factors affecting reverberation time? Explain how it can be
optimized by controlling these factors.
(6 marks)
00
2.b.
Calculate the natural frequency of vibrations for a quartz plate of thickness
5.5 mm. $(Y = 8 \times 10^{10} N/m^{2}$ and $\rho = 2650 kg/m^{3})$
(3 marks)
00
2.c.
Explain with a suitable diagram how the principle of interference is used
in an anti-reflection coating. Derive an expression for its thickness.
(3 marks)
00
3.a.
State the phenomena of double refraction. Hence explain Huygen’s theory
of double refraction.
(6 marks)
00
3.b.
State the characteristics of laser beam and explain any one of them in
brief.
(3 marks)
00
3.c.
What is Fermi Dirac probability distribution function? Give the meaning
of all terms in it.
(3 marks)
00
OR
4.a.
What is photo-voltaic effect? Explain the construction and working of
solar cell. Also draw the IV characteristics of solar cell & define fill
factor.
(6 marks)
00
4.b.
Calculate the number of acceptors to be added in germanium sample to
obtain the resistivity of 20 $\Omega$ cm. Given:- $\mu_{h} = 1700 cm^{2}/V.sec, e =1.6 \times 10^{-19}C$
(3 marks)
00
4.c.
What is difference between normal photography and holography? which
property of lasers is most useful to record a hologram?
(3 marks)
00
5.a.
State and explain Heisenberg’s uncertainty principle. Illustrate it by an
experiment of diffraction at a single slit.
(6 marks)
00
5.b.
State de-Broglie hypothesis of matter waves. Derive the expression for
matter waves for an accelerating particle in terms of its kinetic energy.
(4 marks)
00
5.c.
Calculate the first energy eigen value of electron in eV trapped in rigid
box of length 1 AU. $(e = 1.6 \times 10^{-19} C, h = 6.63 \times 10-^{-34} J-sec, m_{e} = 9.1 \times 10^{-31} kg)$
(3 marks)
00
OR
6.a.
Derive equation of energy when a particle is confined to an infinite potential
well. Draw first three energy levels for an electron confined in it.
(6 marks)
00
6.b.
Explain wave-function $\psi$. Give the physical significance of $| \psi^{2}|$ .
(4 marks)
00
6.c.
A proton and an alpha particle are accelerated by the same potential
difference. Find the ratio of their de-Broglie wavelength. ($m_{\alpha} = 6.68 0^{-27}
kg$, charge on alpha particle = 2 $\times$ Charge on electron, $m_{p}= 1.673 \times 10^{-27} kg$)
(3 marks)
00
7.a.
What is superconductivity? Explain BCS theory of superconductors.
(6 marks)
00
7.b.
Explain the mechanical method, high energy ball milling to synthesize
nanoparticles with the help of a neat and suitable diagram.
(4 marks)
00
7.c.
The critical temperature for lead is 7.2 K. However at 5 K it loses its
superconductivity when subjected to a magnetic field of $3.3×10^{4} A/m$.
Find the maximum value of critical magnetic field which will allow the
metal to retain its superconductivity at 0 K.
(3 marks)
00
OR
8.a.
Explain the optical and electrical properties of nano particles.
(6 marks)
00
8.b.
Give any four points to distinguish between Type I & Type II
superconductors.
(4 marks)
00
8.c.
List the applications of nanotechnology in the field of automobile. Explain
any one application in brief.
(3 marks)
00
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