Stacking fault energy in crystals affects:
A Dislocation mobility
B Band gap
C Nuclear radius
D Electron mass
Lower stacking fault energy widens partial dislocations and increases ductility.
A reciprocal lattice vector G satisfies:
A G·R = 0
B e^(iG·R) = 1
C G = R
D G = 0
This ensures periodicity in reciprocal space.
ARPES (Angle-resolved photoemission spectroscopy) is used to study:
A Nuclear levels
B Phonons only
C Electronic band structure
D Magnetic dipoles
ARPES maps energy–momentum relations in solids.
Thermal expansion in solids occurs because of:
A Harmonic potential
B Anharmonic potential
C Zero-point motion
D Electron drift
Anharmonicity causes average spacing to increase with temperature.
Larmor radius of a charged particle is proportional to:
A Magnetic field
B Electric field
C Perpendicular momentum
D Charge squared
r = p⊥ / (qB).
Effective density of states in a semiconductor conduction band is proportional to:
A T
B (m* T)^(3/2)
C E²
D √E
Nc ∝ (m*_e T)^(3/2).
Thermionic emission follows:
A Planck’s law
B Newton cooling law
C Richardson–Dushman equation
D Coulomb’s law
J ∝ T² e^(−ϕ/kT).
Schottky barrier height depends mainly on:
A Doping level only
B Gate voltage
C Semiconductor thickness
D Metal work function and semiconductor electron affinity
ΦB = Φ_m – χ_s.
Crossover distortion in push–pull amplifiers is caused by:
A Excessive gain
B Delay in capacitors
C Dead zone around zero voltage
D High-frequency instability
Transistors do not conduct until threshold is exceeded.
Negative feedback improves amplifier:
A Noise
B Stability and bandwidth
C Distortion
D Input resistance
Feedback increases linearity and widens bandwidth.
Constant Fraction Discriminator (CFD) is used to:
A Measure charge
B Reduce pile-up
C Reduce timing walk
D Increase pulse height
CFD triggers at same fraction of pulse amplitude.
Cyclotron frequency is independent of:
A Charge
B Magnetic field
C Mass
D Particle velocity (non-relativistic)
f = qB / (2πm) if v ≪ c.
Nuclear force is:
A Long range
B Electromagnetic in nature
C Short range and charge independent
D Strongly repulsive at all distances
Strong force is short range and nearly independent of charge.
Gamow factor explains:
A Fission
B Alpha decay tunneling
C Fusion barrier reduction
D β-decay
Gamow factor calculates tunneling probability through Coulomb barrier.
Neutron activation analysis detects elements by:
A Measuring electron capture
B Counting alpha particles
C Detecting gamma rays from activated nuclei
D Measuring lattice vibrations
Capture → radioactive nucleus → γ emission.
Beam emittance describes:
A Beam charge
B Beam energy only
C Area in phase space
D Number of electrons
Emittance measures transverse beam quality.
Quark model classifies hadrons using:
A Charge only
B Color only
C Flavor and color quantum numbers
D Only mass
Hadrons are color singlets with specific quark flavors.
Gluons mediate:
A Electromagnetic force
B Strong force between quarks
C Weak force
D Gravitational force
Gluons are gauge bosons of QCD.
CP violation implies:
A Parity always conserved
B Time reversal must also violate to preserve CPT
C Mass increases
D Charge conservation breaks
If CP is violated but CPT holds, then T must violate.
Lepton universality means:
A All leptons have same mass
B Leptons do not participate in weak force
C Coupling strength of W boson to e, μ, τ is same
D Neutrinos never mix
SM assumes identical weak coupling for all leptons.
The ratio c/a helps identify:
A Atomic mass
B Crystal symmetry (e.g., tetragonal, hexagonal)
C Electron energy levels
D Nuclear spin
Lattice symmetry depends on axis lengths.
Dislocation climb is caused by:
A Electron movement
B Vacancy diffusion
C Shear stress
D Phonon scattering
Dislocations move perpendicular to slip plane via vacancy motion.
Hume–Rothery rules predict:
A Nuclear fission probability
B Magnetic susceptibility
C Solid-solution formation
D Beta decay probability
Rules relate atomic size, valence, and electronegativity.
Band bending in semiconductors occurs due to:
A Zero temperature
B Surface states and built-in electric fields
C Magnetic fields
D Optical absorption
Surface charges modify energy bands near interface.
Diffusion length of minority carriers is:
A L = μτ
B L = Eτ
C L = √(Dτ)
D L = Dτ
Follows diffusion equation.
A varactor diode operates by:
A Forward conduction
B Changing depletion capacitance with reverse bias
C Thermal breakdown
D Tunneling current
Reverse bias changes depletion width → capacitance changes.
For large open-loop gain, closed-loop gain of an amplifier is approximately:
A A
B 1/A
C 1/β
D β
When Aβ ≫ 1, closed-loop gain ≈ 1/β.
Thermal runaway in BJTs happens because:
A Negative feedback
B Decreasing temperature
C Collector resistance increases
D Higher temperature → higher collector current → more heating
Positive feedback loop between heat and current.
Neutrino was proposed to conserve:
A Charge
B Mass
C Angular momentum & energy in β-decay
D Pressure
Explains continuous β-spectrum and conservation laws.
In two-neutrino double beta decay, emitted particles include:
A One electron
B Two electrons + two antineutrinos
C Two positrons
D Only gamma rays
(A, Z) → (A, Z+2) + 2e⁻ + 2ν̄.
Time-of-flight detectors measure:
A Energy directly
B Charge
C Velocity from path length and elapsed time
D Nuclear charge
v = L/t.
Transition radiation is emitted when:
A Particles slow down
B Particles collide
C Relativistic charged particles cross boundaries of different media
D Neutrons are absorbed
Caused by dielectric discontinuity.
Gell-Mann–Nishijima formula relates charge to:
A Spin
B Strangeness and isospin
C Fermi energy
D Lattice spacing
Q = I₃ + (B + S)/2.
Baryon number conservation forbids:
A β-decay
B p → e⁺ + γ
C n → p + e⁻ + ν̄
D α-decay
Baryon number changes by 1 → forbidden.
Running coupling in QFT means:
A Coupling constant stays fixed
B Mass increases with time
C Coupling depends on energy scale
D Momentum becomes imaginary
Renormalization group describes scale dependence.
Trap states in semiconductors cause:
A Increased band gap
B Infinite carrier mobility
C Carrier capture and recombination
D Superconductivity
Traps reduce carrier lifetime and increase noise.
Mott transition refers to:
A Insulator → metal due to temperature
B Metal → insulator due to electron correlations
C Melting of solids
D Nuclear fusion
Strong interactions localize electrons.
Drude model explains conductivity using:
A Electrons as waves
B Electrons with mean free time τ
C Quantum states only
D Proton motion
σ = ne²τ/m.
Fowler–Nordheim equation describes:
A Avalanche current
B Breakdown voltage
C Field emission tunneling
D Superconducting gap
High-field tunneling through triangular barrier.
CMOS circuits consume low power because:
A They are superconducting
B Transistors are bipolar
C Static current is nearly zero
D Output resistance is high
Only switching events consume power.
The r-process in astrophysics forms heavy nuclei by:
A Rapid proton capture
B Slow neutron capture
C Rapid neutron capture
D Fusion
Occurs in neutron-rich environments like supernovae.
Muons traveling near light speed appear to live longer due to:
A Length contraction
B Time dilation
C Mass increase
D Energy loss
Observers see extended lifetime due to relativistic time dilation.
Cherenkov angle θ satisfies cosθ = c/(nv). Thus increasing velocity:
A Decreases θ to zero
B Has no effect
C Increases θ
D Eliminates radiation
Larger v → larger Cherenkov angle.
CP violation requires CKM matrix to have:
A Zero entries
B Infinite mass
C Real parameters
D A complex phase
Complex phase leads to CP violation.
Phonons are bosons because they have:
A Spin 1/2
B Spin 1
C Integer (zero) spin
D Undefined spin
Phonons have spin 0.
Fermi–Dirac distribution at T = 0 is:
A Linear
B Step function
C Gaussian
D Constant
All states below EF filled, above EF empty.
Johnson–Nyquist noise depends on:
A Pressure
B Voltage
C Temperature
D Light
Thermal noise voltage ∝ √(kT).
Shot noise originates from:
A Thermal agitation
B Quantized charge carriers
C Magnetic field
D Lattice vibrations
Comes from discrete arrival of electrons.
The top quark was discovered in 1995 at:
A CERN
B Fermilab Tevatron
C Brookhaven
D SLAC
Discovered by CDF and DØ collaborations.
CPT theorem implies that if CP is violated, then:
A C must be conserved
B T must be violated
C P must be conserved
D CPT must break
CP violation + CPT conservation → T violation.