Are flashcards effective for the GRE Physics test?

Yes. The GRE Physics exam rewards instant recall of laws, equations, and constants across nine areas, so active recall — pulling an answer from memory — is ideal. Short, spaced flashcard sessions make formulas like the Lorentz factor, the Schrodinger equation, and Carnot efficiency automatic, which is exactly what the timed test demands.

What topics do the GRE Physics flashcards cover?

All nine content areas: classical mechanics (energy, momentum, rotation, Lagrangian), electromagnetism (Maxwell's equations, circuits, induction), optics and waves, thermodynamics and statistical mechanics, quantum mechanics (the Schrodinger equation, operators, spin), atomic physics, special relativity, laboratory methods, and specialized topics in nuclear, particle, condensed-matter, and astrophysics.

How should I study with these GRE Physics flashcards?

Lead with the highest-weighted areas — Classical Mechanics and Electromagnetism are about 38% of the test combined — then quantum mechanics and atomic physics. Mix the modes: flip to learn, type to test recall, match for speed, and quiz to check yourself before working full practice questions.

Are the GRE Physics flashcards free?

Yes — 100% free, all four study modes, no paywall.

Do these flashcards match the current GRE Physics Subject Test?

Yes. The cards are organized to the current ETS GRE Physics content areas and their approximate weighting, covering the undergraduate physics the test measures. They pair with our free GRE Physics practice test and study guide for a complete prep loop.

$ \vec F = m\vec a $ — net force equals mass times acceleration (more generally $ \vec F = d\vec p/dt $).

Net work equals the change in kinetic energy: $ W_{net} = \Delta KE = \tfrac{1}{2}mv_f^2 - \tfrac{1}{2}mv_i^2 $.

$ \vec p = m\vec v $; conserved when no net external force acts.

Impulse-momentum theorem

$ \vec J = \int \vec F\,dt = \Delta \vec p $ — impulse equals change in momentum.

Elastic collision (equal masses, one at rest)

The velocities are exchanged: the incoming mass stops and the struck mass moves off at the original speed.

Perfectly inelastic collision

Objects stick together; momentum is conserved (they move at the center-of-mass velocity) but kinetic energy is not.

Centripetal acceleration

$ a_c = \dfrac{v^2}{r} $, directed toward the center of the circular path.

$ F_c = \dfrac{mv^2}{r} = m\omega^2 r $, pointing toward the center.

Acceleration on a frictionless incline (angle θ)

$ a = g\sin\theta $ down the slope.

$ F = -kx $ — the restoring force of an ideal spring, proportional to displacement.

Angular frequency of a mass-spring system

$ \omega = \sqrt{\dfrac{k}{m}} $.

Period of a simple pendulum

$ T = 2\pi\sqrt{\dfrac{L}{g}} $ (small oscillations).

Simple harmonic motion

Motion under a restoring force proportional to displacement: $ x(t) = A\cos(\omega t + \phi) $.

$ \vec\tau = \vec r\times\vec F $; the rotational analog of force, with $ \tau = I\alpha $.

$ I = \sum m_i r_i^2 $ (or $ \int r^2\,dm $) — rotational analog of mass.

Parallel-axis theorem

$ I = I_{cm} + Md^2 $, where $ d $ is the distance from the center-of-mass axis to the parallel axis.

Moment of inertia of a thin rod about its end

$ I = \tfrac{1}{3}ML^2 $ (about its center it is $ \tfrac{1}{12}ML^2 $).

Moment of inertia of a solid sphere (center)

$ I = \tfrac{2}{5}MR^2 $; about a tangent axis it is $ \tfrac{7}{5}MR^2 $.

$ \vec L = I\vec\omega $ (or $ \vec r\times\vec p $); conserved when no external torque acts.

Rotational kinetic energy

$ KE_{rot} = \tfrac{1}{2}I\omega^2 $.

Why a spinning skater speeds up pulling in her arms

Conservation of angular momentum $ I\omega = $ constant — reducing $ I $ raises $ \omega $; her rotational KE increases (work done pulling in).

Newton's law of universal gravitation

$ F = \dfrac{Gm_1 m_2}{r^2} $.

$ v_{esc} = \sqrt{\dfrac{2GM}{R}} $; independent of the escaping object's mass, $ \sqrt{2}\times $ the surface orbital speed.

$ T^2 \propto a^3 $ — the square of the orbital period is proportional to the cube of the semi-major axis.

A planet sweeps equal areas in equal times — a consequence of angular-momentum conservation; it moves fastest at perihelion.

$ L = T - V $ (kinetic minus potential energy) in generalized coordinates.

Euler-Lagrange equation

$ \dfrac{d}{dt}\dfrac{\partial L}{\partial \dot q} - \dfrac{\partial L}{\partial q} = 0 $ for each generalized coordinate.

$ H = T + V $ — total energy in coordinates and momenta; Hamilton's equations $ \dot q = \partial H/\partial p,\ \dot p = -\partial H/\partial q $.

Generalized (canonical) momentum

$ p_i = \dfrac{\partial L}{\partial \dot q_i} $ — conserved if $ L $ does not depend on $ q_i $ (a cyclic coordinate).

Coriolis acceleration

$ \vec a_{Cor} = -2\,\vec\omega\times\vec v $ in a rotating frame; deflects motion to the right in the Northern Hemisphere.

Centrifugal acceleration (rotating frame)

$ -\vec\omega\times(\vec\omega\times\vec r) $, pointing outward; magnitude $ \omega^2 r $.

Tsiolkovsky rocket equation

$ \Delta v = v_e \ln\!\dfrac{m_i}{m_f} $ — change in speed from exhaust speed and the initial-to-final mass ratio.

Reduced mass (two-body problem)

$ \mu = \dfrac{m_1 m_2}{m_1 + m_2} $ — converts a two-body problem into an equivalent one-body problem.

Period of a physical pendulum

$ T = 2\pi\sqrt{\dfrac{I}{mgd}} $, where $ d $ is the pivot-to-center-of-mass distance.

$ P = \dfrac{dW}{dt} = \vec F\cdot\vec v $.

A force whose work is path-independent and equals minus a potential-energy change; $ \vec F = -\nabla U $.

Friction force (kinetic)

$ f_k = \mu_k N $, opposing motion; static friction satisfies $ f_s \le \mu_s N $.

The constant speed where drag balances gravity, so net force and acceleration are zero.

$ F = \dfrac{1}{4\pi\varepsilon_0}\dfrac{q_1 q_2}{r^2} $ — force between two point charges.

Electric field of a point charge

$ E = \dfrac{1}{4\pi\varepsilon_0}\dfrac{q}{r^2} $, directed radially.

$ \oint \vec E\cdot d\vec A = \dfrac{Q_{enc}}{\varepsilon_0} $ — electric flux through a closed surface equals enclosed charge over $ \varepsilon_0 $.

Electric field inside a conductor (electrostatic equilibrium)

Zero; any excess charge resides on the conductor's surface.

Electric potential energy / potential

$ U = \dfrac{1}{4\pi\varepsilon_0}\dfrac{q_1 q_2}{r} $; potential of a point charge $ V = \dfrac{1}{4\pi\varepsilon_0}\dfrac{q}{r} $.

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GRE Physics Flashcards

Newton's second law: $\vec F = m\vec a$ — net force equals mass times acceleration (more generally $\vec F = d\vec p/dt$ ).
Work-energy theorem: Net work equals the change in kinetic energy: $W_{net} = \Delta KE = \tfrac{1}{2}mv_f^2 - \tfrac{1}{2}mv_i^2$ .
Kinetic energy: $KE = \tfrac{1}{2}mv^2$ .
Gravitational potential energy (near Earth): $U = mgh$ .
Momentum: $\vec p = m\vec v$ ; conserved when no net external force acts.
Impulse-momentum theorem: $\vec J = \int \vec F\,dt = \Delta \vec p$ — impulse equals change in momentum.
Elastic collision (equal masses, one at rest): The velocities are exchanged: the incoming mass stops and the struck mass moves off at the original speed.
Perfectly inelastic collision: Objects stick together; momentum is conserved (they move at the center-of-mass velocity) but kinetic energy is not.
Centripetal acceleration: $a_c = \dfrac{v^2}{r}$ , directed toward the center of the circular path.
Centripetal force: $F_c = \dfrac{mv^2}{r} = m\omega^2 r$ , pointing toward the center.
Acceleration on a frictionless incline (angle θ): $a = g\sin\theta$ down the slope.
Hooke's law: $F = -kx$ — the restoring force of an ideal spring, proportional to displacement.
Angular frequency of a mass-spring system: $\omega = \sqrt{\dfrac{k}{m}}$ .
Period of a simple pendulum: $T = 2\pi\sqrt{\dfrac{L}{g}}$ (small oscillations).
Simple harmonic motion: Motion under a restoring force proportional to displacement: $x(t) = A\cos(\omega t + \phi)$ .
Torque: $\vec\tau = \vec r\times\vec F$ ; the rotational analog of force, with $\tau = I\alpha$ .
Moment of inertia: $I = \sum m_i r_i^2$ (or $\int r^2\,dm$ ) — rotational analog of mass.
Parallel-axis theorem: $I = I_{cm} + Md^2$ , where $d$ is the distance from the center-of-mass axis to the parallel axis.
Moment of inertia of a thin rod about its end: $I = \tfrac{1}{3}ML^2$ (about its center it is $\tfrac{1}{12}ML^2$ ).
Moment of inertia of a solid sphere (center): $I = \tfrac{2}{5}MR^2$ ; about a tangent axis it is $\tfrac{7}{5}MR^2$ .
Angular momentum: $\vec L = I\vec\omega$ (or $\vec r\times\vec p$ ); conserved when no external torque acts.
Rotational kinetic energy: $KE_{rot} = \tfrac{1}{2}I\omega^2$ .
Why a spinning skater speeds up pulling in her arms: Conservation of angular momentum $I\omega =$ constant — reducing $I$ raises $\omega$ ; her rotational KE increases (work done pulling in).
Newton's law of universal gravitation: $F = \dfrac{Gm_1 m_2}{r^2}$ .
Escape velocity: $v_{esc} = \sqrt{\dfrac{2GM}{R}}$ ; independent of the escaping object's mass, $\sqrt{2}\times$ the surface orbital speed.
Kepler's third law: $T^2 \propto a^3$ — the square of the orbital period is proportional to the cube of the semi-major axis.
Kepler's second law: A planet sweeps equal areas in equal times — a consequence of angular-momentum conservation; it moves fastest at perihelion.
Lagrangian: $L = T - V$ (kinetic minus potential energy) in generalized coordinates.
Euler-Lagrange equation: $\dfrac{d}{dt}\dfrac{\partial L}{\partial \dot q} - \dfrac{\partial L}{\partial q} = 0$ for each generalized coordinate.
Hamiltonian: $H = T + V$ — total energy in coordinates and momenta; Hamilton's equations $\dot q = \partial H/\partial p,\ \dot p = -\partial H/\partial q$ .
Generalized (canonical) momentum: $p_i = \dfrac{\partial L}{\partial \dot q_i}$ — conserved if $L$ does not depend on $q_i$ (a cyclic coordinate).
Coriolis acceleration: $\vec a_{Cor} = -2\,\vec\omega\times\vec v$ in a rotating frame; deflects motion to the right in the Northern Hemisphere.
Centrifugal acceleration (rotating frame): $-\vec\omega\times(\vec\omega\times\vec r)$ , pointing outward; magnitude $\omega^2 r$ .
Tsiolkovsky rocket equation: $\Delta v = v_e \ln\!\dfrac{m_i}{m_f}$ — change in speed from exhaust speed and the initial-to-final mass ratio.
Reduced mass (two-body problem): $\mu = \dfrac{m_1 m_2}{m_1 + m_2}$ — converts a two-body problem into an equivalent one-body problem.
Period of a physical pendulum: $T = 2\pi\sqrt{\dfrac{I}{mgd}}$ , where $d$ is the pivot-to-center-of-mass distance.
Power: $P = \dfrac{dW}{dt} = \vec F\cdot\vec v$ .
Conservative force: A force whose work is path-independent and equals minus a potential-energy change; $\vec F = -\nabla U$ .
Friction force (kinetic): $f_k = \mu_k N$ , opposing motion; static friction satisfies $f_s \le \mu_s N$ .
Terminal velocity: The constant speed where drag balances gravity, so net force and acceleration are zero.
Coulomb's law: $F = \dfrac{1}{4\pi\varepsilon_0}\dfrac{q_1 q_2}{r^2}$ — force between two point charges.
Electric field of a point charge: $E = \dfrac{1}{4\pi\varepsilon_0}\dfrac{q}{r^2}$ , directed radially.
Gauss's law: $\oint \vec E\cdot d\vec A = \dfrac{Q_{enc}}{\varepsilon_0}$ — electric flux through a closed surface equals enclosed charge over $\varepsilon_0$ .
Electric field inside a conductor (electrostatic equilibrium): Zero; any excess charge resides on the conductor's surface.
Electric potential energy / potential: $U = \dfrac{1}{4\pi\varepsilon_0}\dfrac{q_1 q_2}{r}$ ; potential of a point charge $V = \dfrac{1}{4\pi\varepsilon_0}\dfrac{q}{r}$ .
Relation between E and V: $\vec E = -\nabla V$ — the field points down the steepest decrease of potential.
Capacitance of a parallel-plate capacitor: $C = \dfrac{\kappa\varepsilon_0 A}{d}$ ; inserting a dielectric $\kappa$ raises the capacitance.
Energy stored in a capacitor: $U = \tfrac{1}{2}CV^2 = \dfrac{Q^2}{2C} = \tfrac{1}{2}QV$ .
Ohm's law: $V = IR$ .
Power dissipated in a resistor: $P = IV = I^2 R = \dfrac{V^2}{R}$ .
Resistors in series vs parallel: Series: $R = R_1 + R_2 + \dots$ . Parallel: $\dfrac{1}{R} = \dfrac{1}{R_1} + \dfrac{1}{R_2} + \dots$ .
Capacitors in series vs parallel: Parallel: $C = C_1 + C_2 + \dots$ . Series: $\dfrac{1}{C} = \dfrac{1}{C_1} + \dfrac{1}{C_2} + \dots$ (opposite of resistors).
RC time constant: $\tau = RC$ — charge on the capacitor relaxes as $e^{-t/\tau}$ .
RL time constant: $\tau = \dfrac{L}{R}$ .
Kirchhoff's rules: Junction rule: currents into a node sum to zero (charge conservation). Loop rule: voltages around a closed loop sum to zero (energy conservation).
Lorentz force: $\vec F = q\vec E + q\vec v\times\vec B$ — force on a charge from electric and magnetic fields.
Magnetic field of a long solenoid: $B = \mu_0 n I$ , where $n$ is turns per unit length.
Ampere's law: $\oint \vec B\cdot d\vec l = \mu_0 I_{enc}$ — gives B from current with high symmetry.
Biot-Savart law: $d\vec B = \dfrac{\mu_0}{4\pi}\dfrac{I\,d\vec l\times\hat r}{r^2}$ — field from a current element.
Force between parallel currents: Attractive when the currents are in the same direction, repulsive when opposite.
Faraday's law of induction: $\varepsilon = -\dfrac{d\Phi_B}{dt}$ — a changing magnetic flux induces an EMF.
Lenz's law: The induced current flows so as to oppose the change in magnetic flux that produced it (the minus sign in Faraday's law).
Self-inductance of a solenoid: Proportional to the square of the number of turns, $L \propto N^2$ (also to area and core permeability).
Energy stored in an inductor: $U = \tfrac{1}{2}LI^2$ .
SI unit of magnetic flux: The weber (Wb); $1\ \text{Wb} = 1\ \text{T}\cdot\text{m}^2$ .
Maxwell's equations: Gauss's law, Gauss's law for magnetism ( $\nabla\cdot\vec B = 0$ ), Faraday's law, and the Ampere-Maxwell law — the four laws of electromagnetism.
Speed of an EM wave in vacuum: $c = \dfrac{1}{\sqrt{\mu_0\varepsilon_0}} \approx 3.0\times10^8$ m/s.
Properties of electromagnetic waves: Transverse, require no medium, travel at $c$ in vacuum, consist of oscillating $\vec E$ and $\vec B$ fields perpendicular to each other and to the motion.
Poynting vector: $\vec S = \dfrac{1}{\mu_0}\vec E\times\vec B$ — energy flux (power per area) carried by an EM field.
Capacitive reactance: $X_C = \dfrac{1}{\omega C}$ ; in a capacitor, current leads voltage by 90°.
Inductive reactance: $X_L = \omega L$ ; in an inductor, current lags voltage by 90°.
Resonance in an LC / RLC circuit: $\omega_0 = \dfrac{1}{\sqrt{LC}}$ — where $X_L = X_C$ and the impedance is minimized.
Magnetic flux: $\Phi_B = \int \vec B\cdot d\vec A$ — the field component through a surface times its area.
Cyclotron frequency: $\omega = \dfrac{qB}{m}$ — angular frequency of a charge circling in a magnetic field.
Principle of superposition (fields): The net electric (or magnetic) field at a point is the vector sum of the fields from each source.
Wave speed relation: $v = \lambda f$ — speed equals wavelength times frequency.
What stays constant when a wave changes medium?: The frequency. The wavelength and speed change, but the frequency is fixed by the source.
Snell's law: $n_1\sin\theta_1 = n_2\sin\theta_2$ — governs refraction at an interface.
Index of refraction: $n = \dfrac{c}{v}$ ; light slows ( $v$ decreases) in a higher-index medium.
Total internal reflection: Occurs when light in a denser medium hits the boundary beyond the critical angle $\theta_c = \sin^{-1}(n_2/n_1)$ ; confines light in optical fibers.
Thin-lens / mirror equation: $\dfrac{1}{f} = \dfrac{1}{d_o} + \dfrac{1}{d_i}$ ; magnification $m = -\dfrac{d_i}{d_o}$ .
Double-slit bright fringes: $d\sin\theta = m\lambda$ — constructive interference at integer path differences.
Single-slit diffraction minima: $a\sin\theta = m\lambda$ ( $m = \pm1, \pm2, \dots$ ) — dark fringes for a slit of width $a$ .
Double-slit fringe spacing: Proportional to the wavelength and inversely proportional to the slit separation: $\Delta y = \dfrac{\lambda L}{d}$ .
Brewster's angle: $\theta_B = \tan^{-1}(n)$ — the incidence angle at which reflected light is fully polarized.
Malus's law: $I = I_0\cos^2\theta$ — intensity of polarized light through a polarizer at angle $\theta$ .
Unpolarized light through a polarizer: Exactly half the intensity, $\tfrac{1}{2}I_0$ , is transmitted (and the output is polarized).
Doppler effect (light): Approaching source → blueshift (higher frequency); receding source → redshift (lower frequency).
Interference vs diffraction: Interference = superposition of waves from multiple sources; diffraction = bending/spreading of a single wave around edges or apertures.
Which phenomenon needs the particle theory of light?: The photoelectric effect. Interference, diffraction, and polarization are all explained by the wave theory.
Diffraction-grating maxima: $d\sin\theta = m\lambda$ ; a grating gives sharp, widely separated orders for spectroscopy.
Rayleigh criterion (resolution): $\theta \approx 1.22\dfrac{\lambda}{D}$ — minimum angular separation a circular aperture of diameter $D$ can resolve.
Standing wave on a string fixed at both ends: $\lambda_n = \dfrac{2L}{n},\ f_n = \dfrac{nv}{2L}$ — harmonics for $n = 1, 2, 3, \dots$ .
Color with the shortest visible wavelength: Violet (refracted/dispersed most by a prism); red has the longest visible wavelength.
Why does a prism disperse light?: The index of refraction depends on wavelength (dispersion), so different colors bend by different amounts.
First law of thermodynamics: $\Delta U = Q - W$ — change in internal energy equals heat added minus work done by the system.
Second law of thermodynamics: The entropy of an isolated system never decreases; heat does not spontaneously flow from cold to hot.
Third law of thermodynamics: The entropy of a perfect crystal approaches zero as the temperature approaches absolute zero.
Ideal gas law: $PV = nRT$ (or $PV = Nk_B T$ ).
Isothermal process: $T$ constant, so $\Delta U = 0$ and $Q = W$ for an ideal gas.
Isobaric process: $P$ constant; work done by the gas is $W = P\,\Delta V$ .
Isochoric (isovolumetric) process: $V$ constant, so $W = 0$ and $Q = \Delta U$ .
Adiabatic process: No heat exchange, $Q = 0$ , so $\Delta U = -W$ ; for an ideal gas $PV^\gamma =$ constant.
Adiabatic free expansion (ideal gas): No work and no heat, so $\Delta U = 0$ ; since $U$ depends only on $T$ , the temperature stays constant.
Carnot efficiency: $\eta = 1 - \dfrac{T_c}{T_h}$ (kelvin) — the maximum efficiency of any engine between two reservoirs.
Entropy change (reversible): $dS = \dfrac{dQ_{rev}}{T}$ ; for a reversible cycle the total entropy change of the universe is zero.
Boltzmann entropy formula: $S = k_B \ln \Omega$ — entropy in terms of the number of accessible microstates $\Omega$ .
Equipartition theorem: Each quadratic degree of freedom contributes $\tfrac{1}{2}k_B T$ to the average energy.
Average translational kinetic energy of a gas molecule: $\langle KE\rangle = \tfrac{3}{2}k_B T$ — independent of molecular mass.
RMS speed of gas molecules: $v_{rms} = \sqrt{\dfrac{3k_B T}{m}}$ — heavier molecules move slower at the same temperature.
Maxwell-Boltzmann distribution: The classical distribution of molecular speeds in an ideal gas; raising $T$ broadens it and shifts the peak to higher speed.
Stefan-Boltzmann law: $P = \sigma A T^4$ — total power radiated by a blackbody is proportional to $T^4$ .
Wien's displacement law: $\lambda_{max} T =$ constant — a hotter blackbody peaks at a shorter wavelength.
Boltzmann constant: $k_B \approx 1.38\times10^{-23}$ J/K — links temperature to energy ( $k_B = R/N_A$ ).
Heat capacity / specific heat: $Q = mc\,\Delta T$ ; for a gas, $C_P - C_V = R$ per mole (Mayer's relation).
Heat pump / refrigerator: Moves heat from cold to hot using external work — a consequence (and demonstration) of the second law.
Fermi-Dirac vs Bose-Einstein statistics: Fermi-Dirac governs fermions (one per state, Pauli); Bose-Einstein governs bosons (many can share a state).
Internal energy of an ideal gas: Depends only on temperature; for a monatomic ideal gas $U = \tfrac{3}{2}nRT$ .
Schrodinger equation (time-independent): $\hat H\psi = E\psi$ — gives the stationary states $\psi$ and their energies $E$ .
Schrodinger equation (time-dependent): $i\hbar\dfrac{\partial \psi}{\partial t} = \hat H\psi$ .
Born rule (probability density): $|\psi(x)|^2$ is the probability density; the probability in $[a,b]$ is $\int_a^b |\psi|^2\,dx$ .
Normalization condition: $\int_{-\infty}^{\infty} |\psi|^2\,dx = 1$ — total probability is one.
Infinite square well energies: $E_n = \dfrac{n^2 h^2}{8mL^2} = \dfrac{n^2\pi^2\hbar^2}{2mL^2}$ , $n = 1, 2, 3, \dots$
Infinite square well wave functions: $\psi_n(x) = \sqrt{\dfrac{2}{L}}\sin\!\left(\dfrac{n\pi x}{L}\right)$ .
Quantum harmonic oscillator energies: $E_n = \left(n + \tfrac{1}{2}\right)\hbar\omega$ — evenly spaced levels with zero-point energy $\tfrac{1}{2}\hbar\omega$ .
Canonical commutator: $[\hat x,\hat p] = i\hbar$ — position and momentum operators do not commute.
Heisenberg uncertainty principle: $\Delta x\,\Delta p \ge \dfrac{\hbar}{2}$ ; an energy-time form is $\Delta E\,\Delta t \ge \dfrac{\hbar}{2}$ .
Hamiltonian operator: $\hat H$ represents the total energy of the system; its eigenvalues are the allowed energies.
Momentum operator: $\hat p = -i\hbar\dfrac{\partial}{\partial x}$ .
Orthonormality of eigenstates: Energy eigenstates are orthogonal and normalized: $\int \psi_m^* \psi_n\,dx = \delta_{mn}$ .
Expectation value: $\langle A\rangle = \int \psi^* \hat A\,\psi\,dx$ — the average measured value of observable $\hat A$ .
Quantum tunneling: A particle has a nonzero probability of passing through a potential barrier even when its energy is below the barrier height.
Electron spin quantum number: $s = \tfrac{1}{2}$ ; the electron is a spin-½ fermion with two spin projections $m_s = \pm\tfrac{1}{2}$ .
Pauli exclusion principle: No two identical fermions can occupy the same quantum state simultaneously.
de Broglie wavelength: $\lambda = \dfrac{h}{p}$ — every particle has a wave nature, demonstrated by electron diffraction.
Ehrenfest's theorem: Quantum expectation values obey the classical equations of motion ( $m\,d\langle x\rangle/dt = \langle p\rangle$ ).
Eigenvalue equation: $\hat A\psi = a\psi$ : a measurement of $\hat A$ on eigenstate $\psi$ yields the eigenvalue $a$ with certainty.
Angular-momentum quantization: $L^2 = l(l+1)\hbar^2$ and $L_z = m_l\hbar$ — magnitude and projection are both quantized.
Bohr model energy levels (hydrogen): $E_n = -\dfrac{13.6\,\text{eV}}{n^2}$ ; the ground state is $-13.6$ eV.
Bohr quantization of angular momentum: $L = n\hbar$ — orbital angular momentum is an integer multiple of $\hbar$ .
Photon energy: $E = hf = \dfrac{hc}{\lambda}$ ; emitted photon energy equals the gap between two atomic levels.
Rydberg formula: $\dfrac{1}{\lambda} = R\left(\dfrac{1}{n_1^2} - \dfrac{1}{n_2^2}\right)$ — wavelengths of hydrogen spectral lines.
Lyman, Balmer, Paschen series: Transitions ending at $n = 1$ (Lyman, UV), $n = 2$ (Balmer, visible), $n = 3$ (Paschen, IR).
Longest-wavelength visible hydrogen line: The $n = 3 \to 2$ Balmer transition (H-alpha) — the smallest energy gap gives the longest wavelength.
Four atomic quantum numbers: Principal $n$ , azimuthal $l$ , magnetic $m_l$ , and spin $m_s$ — they label every electron state.
Photoelectric effect: $KE_{max} = hf - \phi$ ; below a threshold frequency no electrons are emitted, evidence for photons.
Work function: $\phi$ , the minimum energy to free an electron from a metal surface.
Fine structure: Small spectral-line splitting from spin-orbit coupling — the electron's spin interacting with its orbital motion.
Hyperfine structure: Even smaller splitting from the interaction between the nuclear spin and the electron cloud.
Zeeman effect: Splitting of atomic energy levels (and spectral lines) in an external magnetic field.
Stark effect: Shifting and splitting of spectral lines in an external electric field (the electric analog of the Zeeman effect).
Stern-Gerlach experiment: An atomic beam splits into discrete components in a non-uniform magnetic field — proof that angular momentum (spin) is quantized.
Compton scattering: $\Delta\lambda = \dfrac{h}{m_e c}(1-\cos\theta)$ — wavelength shift of an X-ray photon scattering off an electron; evidence for photon momentum.
Electron diffraction (Davisson-Germer): Electrons form interference patterns, demonstrating their wave nature (wave-particle duality).
Hund's rule: Electrons fill degenerate orbitals singly with parallel spins before pairing, to minimize energy.
Aufbau principle: Electrons fill the lowest-energy orbitals first when building up an atom's ground-state configuration.
Selection rule for dipole transitions: $\Delta l = \pm1$ (and $\Delta m_l = 0, \pm1$ ) — allowed electric-dipole transitions.
X-ray production (characteristic lines): An inner-shell vacancy filled by an outer electron emits a characteristic X-ray; K-alpha is $n=2 \to 1$ .
What keeps the electron from falling into the nucleus?: The uncertainty principle: confining the electron more tightly raises its momentum (and energy), setting a minimum-energy ground state.
Two postulates of special relativity: (1) The laws of physics are the same in all inertial frames. (2) The speed of light $c$ is the same for every observer.
Lorentz factor: $\gamma = \dfrac{1}{\sqrt{1 - v^2/c^2}}$ — scales time dilation, length contraction, and energy.
Time dilation: $\Delta t = \gamma\,\Delta t_0$ — a moving clock runs slow; $\Delta t_0$ is the proper time in the clock's rest frame.
Length contraction: $L = \dfrac{L_0}{\gamma}$ — a moving object is shortened along its direction of motion; $L_0$ is the proper length.
Proper time: The time interval measured by a clock at rest relative to the two events — the shortest possible interval between them.
Lorentz transformation: $x' = \gamma(x - vt),\ t' = \gamma\!\left(t - \dfrac{vx}{c^2}\right)$ — relates coordinates between inertial frames.
Relativistic energy: $E = \gamma mc^2$ ; rest energy is $E_0 = mc^2$ .
Relativistic momentum: $\vec p = \gamma m\vec v$ .
Energy-momentum relation: $E^2 = (pc)^2 + (mc^2)^2$ ; for a photon $E = pc$ , at rest $E = mc^2$ .
Relativistic kinetic energy: $KE = (\gamma - 1)mc^2$ — reduces to $\tfrac{1}{2}mv^2$ at low speed and grows without bound as $v\to c$ .
Relativistic velocity addition: $u' = \dfrac{u + v}{1 + uv/c^2}$ — keeps the result below $c$ .
Invariant spacetime interval: $\Delta s^2 = (c\Delta t)^2 - \Delta x^2$ — the same for all inertial observers.
Relativistic Doppler effect: Includes time dilation, so it differs from the classical Doppler shift; receding source → redshift, approaching → blueshift.
Twin paradox resolution: The traveling twin accelerates and decelerates, breaking the symmetry, so that twin ages less.
Why can't a massive object reach c?: Its kinetic energy $(\gamma-1)mc^2$ diverges as $v\to c$ — infinite energy would be required.
Random vs systematic error: Random error scatters measurements (reduced by averaging); systematic error biases them in one direction (a calibration/offset problem).
Adding independent uncertainties: They add in quadrature: $\sigma = \sqrt{\sigma_1^2 + \sigma_2^2}$ .
Poisson counting statistics: A count of $N$ events has uncertainty $\sqrt{N}$ ; the fractional uncertainty $1/\sqrt{N}$ shrinks with more data.
Standard deviation vs standard error: Standard deviation measures spread; the standard error of the mean is $\sigma/\sqrt{N}$ .
Lock-in amplifier: Extracts a small signal at a known reference frequency from heavy noise, by mixing and low-pass filtering, hugely improving signal-to-noise.
Faraday cage: A conducting enclosure that shields its contents from external electric fields (charges redistribute to cancel the field inside).
Cryostat with liquid helium: Provides thermal insulation to reach and hold temperatures near absolute zero; liquid helium boils at 4.2 K.
Laser (Doppler) cooling: Slows and cools atoms using laser light tuned just below an atomic transition, reducing their kinetic energy.
Optical tweezers: Trap and move microscopic particles using the radiation pressure (momentum) of a focused laser beam.
Hall effect measurement: Measures the carrier density (and sign of charge carriers) in a material from the transverse Hall voltage in a magnetic field.
Time-of-flight mass spectrometry: Determines an ion's mass-to-charge ratio from the time it takes to travel a known distance after acceleration.
FTIR spectroscopy advantage: Fourier-transform IR offers higher resolution, faster acquisition, and better signal-to-noise (Fellgett's advantage) over dispersive IR.
Oscilloscope: Displays voltage versus time, used to view waveforms, measure amplitude, frequency, and phase.
Significant figures rule: A computed result is limited by the least-precise input; report uncertainty to one or two significant figures.
Photomultiplier tube: Detects single photons by cascading secondary-electron emission, producing a measurable pulse from very weak light.
Geiger-Muller counter: Detects ionizing radiation via gas ionization producing electrical pulses; counts follow Poisson statistics.
Nuclear magic numbers: 2, 8, 20, 28, 50, 82, 126 — proton or neutron counts that fill nuclear shells and give extra stability.
Nuclear binding energy: The energy released forming a nucleus from its nucleons; the mass defect times $c^2$ . Iron-56 has the highest binding energy per nucleon.
Alpha, beta, gamma decay: Alpha emits a $\ce{^4_2He}$ nucleus; beta emits an electron/positron (plus a neutrino); gamma emits a high-energy photon.
Radioactive decay law: $N(t) = N_0 e^{-\lambda t}$ ; the half-life is $t_{1/2} = \dfrac{\ln 2}{\lambda}$ .
Color confinement: Quarks carry color charge and can never be isolated — only color-neutral hadrons (mesons, baryons) are observed.
Quark model: Baryons are three quarks (e.g. proton = uud), mesons are a quark-antiquark pair; the six flavors are u, d, c, s, t, b.
The four fundamental forces: Strong, electromagnetic, weak, and gravity — mediated by gluons, photons, W/Z bosons, and (hypothetically) gravitons.
Superconductivity: Zero electrical resistance below a critical temperature; expels magnetic fields (Meissner effect).
Superfluidity: Flow with zero viscosity, seen in liquid helium-4 below 2.17 K — particles flow without losing kinetic energy.
Chandrasekhar limit: The maximum white-dwarf mass (≈ 1.4 solar masses) supported by electron degeneracy pressure; above it the core collapses.

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By Career EmployerUpdated Sep 12, 2026

200+ free GRE Physics flashcards — 4 ways to study

GRE Physics Flashcard of the DayNew daily

The classic card. Do you know this one?

Click Study Flashcards above to open the flashcard hub — 200 GRE Physics cards you can flip, match, type, or quiz yourself on. Every card is drawn from the ETS content areas, so you study exactly what the test measures.^[1] Pair them with our free practice test and study guide.

GRE Physics Flashcard Study Modes

Four modes run on the same deck. Flip is plain study, front to back, at your own pace. Match is a timed term-to-definition game that rewards fast recognition. Type shows the definition and asks you to produce the term, so a card like Brewster’s angle has to come from memory, not from a list. Quiz turns the cards into multiple choice for a quick check.

Free GRE Physics flashcards from Career Employer — active recall for the GRE Physics Subject Test

Why Flashcards Work for the GRE Physics Test

Classical Mechanics is the largest domain at 40 cards, and it drills the vocabulary and relations that show up everywhere else on the GRE Physics test. You get core quantities such as Torque and Momentum alongside the formalism cards, including Lagrangian and Hamiltonian, plus staples like Hooke’s law and Escape velocity that you should be able to state without hesitation.

Electromagnetism follows with 35 cards built around the named laws and the definitions that hang off them. Gauss’s law, Ampere’s law, and Lenz’s law sit next to Coulomb’s law and the Lorentz force, with supporting terms like Magnetic flux and Ohm’s law filling in the circuit and field language you need to read a problem quickly.

Thermodynamics & Statistical Mechanics carries 23 cards covering process types and constants, from Adiabatic process and Isothermal process to Carnot efficiency and the Equipartition theorem. Atomic Physics adds 21 cards on spectra and structure, where the Zeeman effect, the Stark effect, and Hund’s rule appear beside the Rydberg formula and Work function.

Optics & Wave Phenomena has 20 cards on propagation and interference, including Snell’s law, Malus’s law, and Total internal reflection. Quantum Mechanics also has 20, drilling operators and results such as the Momentum operator, the Canonical commutator, and de Broglie wavelength.

The remaining three domains reward cheap points. Laboratory Methods holds 16 cards on instruments like the Lock-in amplifier and the Photomultiplier tube. Special Relativity has 15, covering Proper time, Length contraction, and the Lorentz factor. Specialized Topics closes with 10, including Superconductivity and the Chandrasekhar limit.

The GRE Physics Subject Test rewards instant recall of laws, equations, and constants across nine areas under tight time pressure.^[2] Spaced flashcards are the most efficient way to make that knowledge automatic. Used alongside our practice test and study guide, they turn review time into measurable progress.

GRE Physics Flashcards by Area

The cards are organized by the GRE Physics test’s nine ETS content areas. Drill the highest-weighted ones first — Classical Mechanics and Electromagnetism anchor the test at about 38% combined:^[1]

GRE Physics flashcards by content area and approximate weighting
Content area	Approx. weight
Classical Mechanics	~20%
Electromagnetism	~18%
Quantum Mechanics	~12%
Atomic Physics	~10%
Thermodynamics & Statistical Mechanics	~10%
Optics & Wave Phenomena	~9%
Specialized Topics (nuclear, particle, condensed matter, astrophysics)	~9%
Special Relativity	~6%
Laboratory Methods	~6%

How to Get the Most Out of These Flashcards

Start heavy. Classical Mechanics is 40 cards and feeds every other domain, so clear it in Flip first, then move to the 35 Electromagnetism cards while the definitions are fresh.
Type the formalism. Cards like Lagrangian and Canonical commutator are easy to recognize and hard to reproduce, so drill them in Type until the wording comes out cleanly.
Match the named laws. The law cards across Electromagnetism and Optics & Wave Phenomena, such as Lenz’s law and Malus’s law, are ideal for timed recognition under Match.
Switch when Quiz stops teaching. Once Quiz rounds run clean across Special Relativity and Thermodynamics & Statistical Mechanics, move to the practice test and let the study guide fill the gaps.
Keep a rotating cadence. Work one or two domains a sitting, then re-Match yesterday’s set, so the 200 cards cycle through review instead of getting studied once and dropped.

GRE Physics Flashcards FAQ

Two hundred free GRE Physics flashcards, organized across all nine ETS content areas — Classical Mechanics, Electromagnetism, Optics and Wave Phenomena, Thermodynamics and Statistical Mechanics, Quantum Mechanics, Atomic Physics, Special Relativity, Laboratory Methods, and Specialized Topics. They're free with no account required.

References

1.ETS. “GRE Subject Tests: Content and Structure.” ETS. ↑
2.ETS. “GRE Physics Test Practice Book.” ETS. ↑
3.NIST. “The NIST Reference on Constants, Units, and Uncertainty.” National Institute of Standards and Technology. ↑

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