Download 102 Applied Physics B.Tech. 1st Year (Term – II)

Roll No. …………………..
Lingaya’s University
B .T ech . 1 s t Year (T er m – I I )
E xami n ati on – Feb 2011
Ap p l i ed Ph ysi cs (PH - 1 02)
[Time: 3 Hours]
[Max. Marks: 100]
Before answering the question, candidate should ensure that they
have been supplied the correct and complete question paper. No
complaint in this regard, will be entertained after examination.
Note: – Attempt five questions in all. All questions carry equal
marks. Question no. 1 is compulsory. Select two questions from
Section B and two questions from Section C.
Section – A
Q-1. Part – A
Select the correct answer of the following multiple
choice questions.
[10x1=10]
(i)
(ii)
(iii)
(iv)
Which of the following has the highest packing fraction?
(a) Simple cubic structure
(b) Body centered cubic structure
(c) face centered cubic structure (d) Diamond structure
The Miller indices of a plane in a simple cubic lattice crystal are
(123), the coordinates of the plane are
(a) (a, b/2, c/2)
(b) (a, b, c)
(c) (a, 2b, 3c)
(d) none of these
Schrodinger wave equation can be written as
(a) H=0
(b) E=0
(c) H-E=0
(d) H +E=0
In case of black body for distribution of energy radiated by a black
body Planck’s formula reduces to Rayleigh Jean’s formula for
(a) Long wavelength region
(b) Short wavelength region
(c) Equal wavelength of radiation (d) none of these
1
(v)
If the Fermi energy of silver at 0K is 5 eV, the mean energy of
electron in silver at 0K will be
(a) 2.5 eV
(b) 3 eV
(c) 5 eV
(d) 10 eV
(vi) The unit of Hall coefficient is
(a) Vm3A-1 Wb-1
(b) Vm2Wb-1
(c) Vm3 AWb-1
(d) Vm2 A-2 Wb
(vii) The E-k curve in the extended zone has discontinuity at n=1,2,3, …
etc. and ‘a’ is the length of the primitive cell
n
( 2 )
a
n
(c) k= 
2a
(a) k= 
n
a
n 2 2
(d) k= 
a
(b) k= 
(viii) Joule Thomson’s coefficient for perfect gas is
(a) zero
(b) positive
(c) negative
(d) none of these
(ix)
(x)
In a ferromagnetic material, susceptibility is
(a) very small and positive
(b) very small and negative
(c) very large and negative
(d) very large and positive
Meissner effect is related to
(a) Optical properties of super conductors
(b) Magnetic properties of super conductors
(c) Thermal properties of super conductors
(d) None of these
Part – B
(a)
(b)
Write a short note on Laue method for crystal structure
determination.
[5]
Distinguish among metals, semiconductors and insulators on
the basis of band theory.
[5]
2
Section – B
Q-2. (a)
(b)
What are the drawbacks of classical free electron theory? [4]
Derive Richardson – Dushman equation of thermionic
emission.
[16]
Q-3. (a)
Derive London’s equations with reference to superconductivity
and define Type I and Type II superconductors.
[10+4]
An electron has a de – Broglie wavelength of 2 pm. Find its
kinetic energy.
(Rest mass energy of electron = 511 keV and velocity of light
C = 3 x 108 m/s)
[6]
(b)
Q-4. (a)
Derive time independent Schrödinger wave equation. Give
physical significance of .
[10+5]
(b)
Calculate the ground state energy of an electron confined to a
1-D box of length 1 Å.
[5]
Section – C
Q-5. (a)
(b)
Q-6. (a)
(b)
What do you mean by point defects in solids? Derive an
expression for the concentration of Schottky defects in a
crystal.
[2+13]
In a simple cubic crystal, find the ratio of spacings of (110) and
(111) planes.
[5]
Give an account of Langevin’s theory of paramagnetism and
prove that susceptibility  of paramagnetic substance is
inversely proportional to the absolute temperature.
There are 2.54 x 1022 free electrons per cm3 in sodium.
Calculate its Fermi energy and Fermi velocity (h = 6.63 x 10-34
J s, m=9.11 x 10-31 kg, kB= 1.38 x 10-23 J/K, 1eV,= 1.6 x 10-19 J)
[12+8]
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Q-7. (a)
(b)
Q-8. (a)
(b)
Define mean square speed, average speed and most probable
speed. Obtain expressions for average speed and most probable
speed.
A 42 kilowatt engine is operating between 227 oC and 177 oC.
Calculate the efficiency of the engine.
[15+5]
What is Hall effect? Give an experimental method of
calculating concentration and type of charges in a given
semiconductor.
Luminosity of Rigel star in Orion constellation is 17000 times
that of the Sun. If the surface temperature of the Sun is 6000 K,
calculate the temperature of the star.
[15+5]
4