The coordination number of an FCC lattice is:
A 6
B 8
C 12
D 4
Each atom in FCC has 12 nearest neighbors.
The plane (100) in a cubic crystal has a normal along:
A y-axis
B x-axis
C z-axis
D body diagonal
(100) plane is perpendicular to x-axis.
Zone folding in reciprocal space causes:
A New Bravais lattices
B Increase in atomic radius
C Opening of band gaps at zone boundaries
D Reduction of electron mass
Folding introduces gaps at Brillouin zone edges.
Rietveld refinement is primarily used to:
A Measure electron mass
B Analyze optical spectra
C Refine crystal structures from powder XRD
D Study nuclear reactions
Rietveld method fits XRD pattern to structural model.
Debye temperature θD relates to:
A Nuclear vibrations
B Fermi energy
C Sound velocity and phonon cutoff
D Band gap
θD is linked to maximum phonon frequency.
Umklapp processes cause:
A Increased electrical conduction
B Momentum non-conservation and thermal resistance
C Perfect heat conduction
D No phonon scattering
Umklapp scatters phonons, increasing resistance.
Fermi energy for free electrons is measured from:
A Core level
B Vacuum level
C Bottom of the energy band
D Lattice potential minimum
EF is defined relative to band bottom.
A band insulator has:
A Overlapping bands
B Partially filled bands
C Completely filled valence band and large band gap
D No band gap
Large Eg prevents conduction.
The critical field Hc(T) of a Type I superconductor decreases with temperature following:
A Exponential law
B Linear law
C Hc(0)[1 − (T/Tc)²]
D Hc(0)/T
Empirical relation for Type I superconductors.
Conductivity of intrinsic semiconductors increases with temperature because:
A Mobility increases
B Band gap widens
C Carrier concentration increases
D Lattice constant expands
More electrons/holes thermally excited.
The dynamic resistance of a Zener diode in breakdown is:
A Very high
B Moderate
C Low
D Zero
Zener region has small slope resistance.
Peak inverse voltage (PIV) of a diode must exceed:
A Average output voltage
B Forward voltage
C Maximum reverse voltage applied
D RMS voltage
To avoid breakdown, PIV ≥ max reverse voltage.
A current mirror reproduces:
A Voltage
B Temperature
C A reference current in another branch
D Power gain
Current mirrors copy bias currents.
Transconductance (gm) of a FET is:
A ∂Vgs/∂Id
B ∂Id/∂Vgs
C Id/Vds
D Vgs/Id
gm indicates sensitivity of drain current to gate voltage.
Barkhausen criterion for oscillation requires:
A Loop gain < 1
B Loop gain = 0
C Loop gain = 1 and phase shift = 0° or 360°
D No feedback
Exact conditions for sustained oscillation.
Liquid drop model treats nucleus as:
A A rigid lattice
B A gas of neutrons and protons
C A charged liquid droplet
D A crystal structure
Accounts for volume, surface, Coulomb, and asymmetry energies.
Radioisotope dating determines:
A Temperature of a sample
B Charge of nucleus
C Age from parent/daughter ratio
D Pressure of sample
Decay law allows computing age.
Positron emission requires threshold energy because:
A Proton is converted to neutron
B Electron is created
C Neutrino is emitted
D Must create e+e⁻ pair mass difference
Requires ≥ 2mₑc² energy.
Semiconductor detectors have good resolution because:
A They are heavy
B Ionization energy is high
C Ionization energy is low
D They use scintillation
Low energy per e–h pair improves resolution.
A LINAC accelerates particles using:
A Magnetic potentials
B DC voltage
C RF electric fields in drift tubes
D Optical lasers only
Alternating RF fields accelerate particles.
Strange particle behavior was explained by introducing:
A Electric charge
B Strangeness quantum number
C Color charge
D Hypercharge only
Conserved in strong interactions but violated in weak.
In elastic scattering, which quantities are conserved?
A Charge only
B Kinetic energy & momentum
C Momentum only
D Mass only
Total kinetic energy remains constant.
Heavy nuclei undergo fission more easily because:
A High binding energy
B Low Coulomb repulsion
C Low binding energy per nucleon
D No shell structure
Lower binding energy makes splitting favorable.
Violation of CPT symmetry would imply:
A Conservation of parity
B Lorentz invariance holds
C No mass–energy equivalence
D Breakdown of fundamental QFT principles
CPT requires Lorentz invariance and locality.
Bloch theorem states ψk(r) is:
A Pure plane wave
B Pure periodic function
C Plane wave × periodic function
D Random function
ψk(r)=u_k(r)e^(ikr).
Effective mass of electrons in crystals:
A Always equals free electron mass
B Can be positive or negative
C Is constant for all bands
D Does not affect transport
m* relates to curvature of E(k).
Electron diffraction uses de Broglie wavelength because electrons:
A Are particles only
B Have no mass
C Exhibit wave–particle duality
D Travel at c
Matter waves produce diffraction.
X-ray absorption edges correspond to:
A Conduction band energies
B Lattice energies
C Core electron binding energies
D Nuclear energies
Sudden jumps occur when photon energy exceeds core-level binding energy.
Thermal conductivity in metals is dominated by:
A Phonons
B Electrons
C Ions
D Vacancies
Electrons carry most heat in metals.
Minority carrier lifetime affects:
A Refractive index
B Diffusion length and switching speed
C Band gap
D Resistivity only
L = √(Dτ); shorter lifetime → faster devices.
Avalanche breakdown occurs due to:
A Thermal vibration
B Photon absorption
C Impact ionization
D Hole diffusion
Carriers accelerate and create secondary carriers.
A Darlington pair is used to:
A Reduce current gain
B Reduce input resistance
C Provide very high current gain
D Lower voltage gain
Overall β ≈ β₁β₂.
At –3 dB frequency, output power is:
A Half of input power
B Equal to input power
C Twice input power
D Zero
–3 dB corresponds to 50% power.
Channel-length modulation in MOSFET causes:
A Infinite output resistance
B Finite output resistance
C No current flow
D Breakdown
Effective channel shortens with Vds.
Type I superconductors exhibit:
A Partial flux penetration
B Two critical fields
C Complete Meissner effect
D No superconductivity at low T
Type I = perfect diamagnetism below Hc.
Non-spherical nuclear charge distribution leads to:
A Dipole moment
B No moments
C Quadrupole moment
D Octupole moment
Quadrupole moment arises from shape deformation.
Radioactive activity A decreases with time as:
A A = A₀e^(−λt)
B A = A₀ + λt
C A = λ/t
D A = constant
Exponential decay law.
Electron capture results in:
A Z increases by 1
B Z decreases by 1
C A increases
D A decreases
p + e⁻ → n → atomic number decreases.
In a proportional counter, pulse height is proportional to:
A Detector voltage
B Background radiation
C Energy deposited by incident radiation
D Gas pressure only
Gas multiplication remains proportional.
Undulators in synchrotron sources produce:
A Weak radiation
B Broad spectrum
C Intense, narrow-band radiation
D No radiation
Interference between periodic magnets.
Baryons consist of:
A 2 quarks
B 3 quarks
C 4 quarks
D 1 quark
Baryons are qqq.
CKM matrix describes:
A Neutrino mixing
B Quark flavor mixing
C Lepton mixing
D Strong interactions
Weak interaction mixes quark flavors.
Rutherford scattering suggested the atom has:
A Uniform charge
B No nucleus
C A small, dense nucleus
D Equal mass distribution
Large-angle scattering proved concentrated positive charge.
Parity violation occurs in:
A Electromagnetic interaction
B Strong interaction
C Weak interaction
D Gravitational interaction
Weak force violates P symmetry.
Miller index (210) represents a plane that:
A Cuts axes at 2a, a, ∞
B Cuts axes at a/2, a/1, a/0
C Cuts axes at a/2, a, ∞
D Is parallel to all axes
(210) intercepts: x=a/2, y=a, z=∞.
A screw dislocation has Burgers vector:
A Perpendicular to dislocation line
B Parallel to dislocation line
C Zero
D Random
Screw dislocation → Burgers vector parallel to line.
Wiedemann–Franz law suggests:
A Electrons and phonons carry heat equally
B Only phonons conduct heat
C Same carriers transport heat and charge
D Resistivity is constant
Electrons carry both heat and charge.
At very low temperatures, an intrinsic semiconductor behaves as:
A Metal
B Semiconductor
C Conductor
D Insulator
Nearly no thermally excited carriers.
Open-circuit voltage of a solar cell depends mainly on:
A Doping only
B Band gap and illumination
C Resistivity
D Thickness only
Voc limited by Eg and recombination.
Control rods in a nuclear reactor work by:
A Absorbing protons
B Absorbing neutrons
C Absorbing electrons
D Absorbing alpha particles
Neutron absorption reduces reactivity.