Find the electric susceptibility of a dielectric gas having dielectric constant of
1.000041.
Calculate the intrinsic carrier concentration for Ge at 270C. [for Ge, Atomic
weight = 72.6, Density = 5400 kg/m3, Band gap = 0.70 eV].
The electronic polarizability of a dielectric material having no ions and permanent dipoles, is 1.5 _ 10�40 farad-m2. The density of the material is 2.5 _
1028 atoms per m3. Calculate the dielectric constant of the material.
Calculate the wavelength of matter wave associated with a neutron whose
kinetic energy is 1.5 times the rest mass of electron.
(Given that Mass of neutron = 1.676 _ 10�27 kg, Mass of electron = 9.1 _
10�31 kg, Planck's constant = 6.62 _ 10�34 J-sec, Velocity of light = 3 _ 108
m/s).
If the effective mass of holes in a semiconductor is 5 times that of electrons, at
what temperature would the Fermi level be shifted by 15% from the middle of
the forbidden energy gap? [Given that the energy gap for the semiconductor
is 1.20 eV].
Calculate the velocity and kinetic energy of an electron having wavelength of
0.21 nm.
An electron is confined to a one dimensional potential box of length 2.12 A0.
Calculate the energies (in eV) corresponding to the second and fourth quantum
states.
Calculate the wavelength of emitted radiation from GaAs which has a band
gap of 1.44 eV.
Find the lowest energy of an electron con_ned to a one-dimensional box of
width 0.1 nm.
The magnetic _eld strength in silicon is 1000 amp/m. If the magnetic field
susceptibility is -0.3 x 10-5, calculate the magnetization and ux density in
silicon. [permeability of vacuum = 4πx10-7 H/m]
The electron concentration in an n-type semiconductor is 5 x1017 per m3.
Calculate the conductivity of the material if the drift velocity of electron is
350 m/s in an electric field of 1000 V/m.
The relaxation time of electrons in a conductor at 300 K is equal to 1.99 x 10-14 sec. Determine the
electrical conductivity of that conductor. [Concentration of electrons = 8.5x1028 per m3]
The numerical aperture of an optical _ber is 0.39. If the di_erence in the
refractive indices of the material of its core and the cladding is 0.05, calculate
the refractive index of material of the core, when the light is launched into it
in air.
Calculate the fractional index change for a given optical _ber if the refractive
indices of the core and the cladding are 1.563 and 1.498 respectively. [8+4+4]
Find the wavelength associated with an electron rose to a potential 1600 V.
Calculate the angle of acceptance of a given optical _ber, if the refractive
indices of the core and the cladding are 1.563 and 1.498 respectively.[6+6+4]
The refractive indices of core and cladding are 1.53 and 1.42 respectively. Then
calculate its critical angle.
Use the Fermi distribution function to obtain the value of F(E) for E - EF =
0.01 eV at 200 K. [6+6+4]
Find the temperature at which there is 1% probability that a state with an
energy of 0.75 eV above Fermi energy will be occupied.
Calculate the refractive indices of core and cladding of an optical _ber with a
numerical aperture of 0.33 and their fractional di_erence of refractive indices
being 0.02.
The Fermi energy of silver is 5.5 eV. An electron in silver has an energy
which is 1% above Fermi energy. At what temperature we can expect a 10%
probability of electron at this energy level?
The dielectric constant of He gas at NTP is 1.0000684. Calculate the electronic
polarizability of He atoms if the gas contains 2.7 × 1025 atoms/m3.
The radias of helium atom is about 0.56AU. Calculate the polarisasbility of
helium and its relative permeability. The number of helium atoms in a volume
of 1 m2 is 2.7 _ 1025 atoms.
The RH of a specimen is 3.66x10-4 m3 c-1. Its resistivity is 8.93x10-3_m. Find mobility
and charge carrier concentration.
A plane transmission grating having 4250 lines per cm is illuminated with sodium light
normally. In second order spectrum the spectral lines are deviated by 30 o are observed.
Find the wavelength of the spectral line.
The optical power launched into an optical fiber is 1.5 mW. The fiber has attenuation of
0.5 db/km. If the power output is 2 μm, calculate the fiber length.
A parallel beam of light ( _ = 5890x10-10m ) is incident on a thin glass plate (μ = 1.5 )
such that the angle of refraction into the plate is 60o. Calculate the smallest thickness of
plate which would appear dark by reflection.
Calculate the number of modes propagating in an optical fiber of core of 6μm diameter,
(given that the indices are 1.45 and 1.44 for core and cladding respectively) while
operated at a wavelength of 0.623 μm.
In Newton’s rings experiment, the diameters of the 4th and 12th dark rings are 0.40 cm
and 0.70 cm respectively. Find the diameter of the 20th dark ring.
A plane transmission grating having 4250 lines per cm is illuminated with sodium light
normally. In second order spectrum the spectral lines are deviated by 30 o are observed.
Find the wavelength of the spectral line.
The optical power launched into an optical fiber is 1.5 mW. The fiber has attenuation of
0.5 db/km. If the power output is 2 μm, calculate the fiber length.
In Newton’s rings experiment, the diameter of the 10th ring changes from 1.40 cm to
1.27
cm when a liquid is introduced between the lens and the plate. Calculate the refractive
index of the liquid.
An electron is bound in one dimensional in_nite well of width 1x10 �10m. Find
the energy value of electron in the ground state and second excited state.
De_ne relaxation time. Find relaxation time of conduction electrons in a
metal of resistivity 1.54 x 10�8 Ohm-m. If the metal has 5.8x1028 conductions
electrons / m3.
The saturation magnetic induction of nickel is 0.65 Wb/m 2. If the density
of nickel is 8906 Kg/m3and its atomic weight is 58.7, calculate the magnetic
moment of the nickel atom in terms of Bohr magneton.
The forbidden gap in pure silicon is 1.1eV. Compare the number of conduction
electrons at temperatures 370C and 270C.
Find the relative permeability of a ferromagnetic material if a _eld of strength
110 A/m produces a magnetization of 3300 A/m.
The dielectric constant of He gas at NTP is 1.0000684. Calculate the electronic
polaizability of He atoms if the gas contains 2.7 x 1025atoms/m3.
An electron is moving in a one dimensional box width 2x10�10m. If the electron
is found in the _rst excited state what is the probability of _nding the electron
between x=0 and x= 1x10�10m. in that state.
Determine the fraction of electrons in conduction band in silicon at 270C and
2270C. given Eg=1.1eV and K=1.38X10�23 J/k.
The area of the hysteresis loop between B and H is 100 m2. Each unit space
along the vertical axis represents 0.001 Wb/m2and each unit space along the
horizontal represents 40A/m. Determine the Hysteresis loss per cycle.
A silicon wafer is doped with 1021 phosphorus atoms. Calculate
(i)The majority carrier concentration (ii)The minority concentration and (iii)The
electrical resistivity of the doped silicon at room temperature of the dopant
(iv)atoms; ni=1.5X1016 /m3, = 0.135m2/V.s and =0.048 m2/V.s
Diamagnetic Al2O3 is subjected to external magnetic field of 105 A/m. Evaluate
magnetization and magnetic flux density in Al2O3. (Susceptibility of Al2O3 = -5x10-5).