# IB Physics HL/SL: Space, Time & Motion, Particulate Nature of Matter, Wave Behaviour, Fields & Nuclear/Quantum Physics

> Complete IBDP Physics (Themes A–E, 2023+ syllabus) revision: kinematics, work/power, rigid body rotational mechanics, special relativity, thermal/greenhouse physics, SHM & wave phenomena, Doppler effect, gravitational/electric/magnetic fields, and quantum/nuclear physics.

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- **Level:** intermediate
- **Languages:** en → en
- **Total Cards:** 32

## Flashcards (32 Cards)

| # | Front (Term / Prompt) | Back (Definition / Answer) | Example | Multiple-Choice Options |
| :--- | :--- | :--- | :--- | :--- |
| 1 | State the First and Second Laws of Thermodynamics and the equations for Isothermal, Isobaric, Isochoric, and Adiabatic gas processes and Carnot Efficiency (HL B.4). | Internal energy of an ideal monatomic gas: U = (3/2)nRT = (3/2)Nk_B T. First Law of Thermodynamics: Q = ΔU + W, where work done BY the gas is W = PΔV (area under a P–V diagram). 1) Isochoric (constant V): W = 0, so Q = ΔU. 2) Isobaric (constant P): W = PΔV. 3) Isothermal (constant T): ΔU = 0, so Q = W. 4) Adiabatic (no heat exchange, rapid/insulated): Q = 0, so ΔU = −W and PV^(5/3) = constant (steeper than isothermals on P–V graph). Entropy change: ΔS = ΔQ / T and S = k_B ln Ω. Maximum Carnot heat engine efficiency: η_Carnot = 1 − (T_cold / T_hot). |  |  |
| 2 | Compare Standing Waves in strings fixed at both ends, open pipes (open at both ends), and closed pipes (closed at one end, open at the other) (C.4). | Displacement Nodes (N) occur at fixed ends/closed pipe ends; Antinodes (A) occur at open pipe ends. 1) String fixed at both ends OR Pipe open at both ends: ALL integer harmonics are present (n = 1, 2, 3, ...), with λ_n = 2L / n and f_n = n × (v / 2L). 2) Pipe closed at one end and open at the other: ONLY ODD harmonics are present (n = 1, 3, 5, ...), with λ_n = 4L / n and f_n = n × (v / 4L) (fundamental L = ¼λ₁). |  |  |
| 3 | In HL Electromagnetic Induction, write the equations for an AC Generator's sinusoidal EMF (ε = N BAω sin(ωt)) and how changing rotation speed ω affects peak EMF and period. | As a coil of N turns and area A rotates at constant angular velocity ω in a uniform magnetic field B, flux linkage is NΦ = NBA cos(ωt). By Faraday's Law, the induced EMF is the negative derivative: ε(t) = −d(NΦ)/dt = NBAω sin(ωt), so peak EMF is ε₀ = NBAω. If the rotational speed ω is DOUBLED, the peak induced EMF (ε₀) DOUBLES AND the period of the AC output (T = 2π/ω) HALVES (frequency doubles). |  |  |
| 4 | State the Doppler Effect equations for Sound (moving source vs moving observer) and Electromagnetic Waves (SL & HL C.5). | For Electromagnetic waves (when Δv ≪ c): Δf / f = Δλ / λ ≈ v / c. For Sound waves (speed v in air, HL): 1) Moving source (speed u_s): f' = f [ v / (v ∓ u_s) ] (use MINUS for source moving TOWARDS observer so frequency increases, PLUS for moving away); 2) Moving observer (speed u_o): f' = f [ (v ± u_o) / v ] (use PLUS for observer moving TOWARDS source, MINUS for moving away). |  |  |
| 5 | State the Single-Slit Diffraction equation (θ = λ / b), Rayleigh Criterion for Resolution, and Multiple-Slit / Diffraction Grating effects (HL C.3). | Single-slit diffraction: angular half-width of the central bright maximum (from centre to first minimum) is θ = λ / b (in radians, where b is slit width). When a double-slit pattern is modulated by single-slit diffraction, bright fringes of spacing s = λD / d lie inside the single-slit envelope. Increasing the number of slits N (towards a diffraction grating, d sin θ = nλ) makes the primary maxima much SHARPER (narrower) and much MORE INTENSE (I ∝ N²), while secondary maxima become negligible. |  |  |
| 6 | How do parallel-plate Capacitors behave when connected in Parallel vs in Series, and what happens when a dielectric (ε_r) is inserted? | Note that capacitor combination formulas are the OPPOSITE of resistor formulas: 1) Capacitors in Parallel (same V across each): C_total = C₁ + C₂ + ...; 2) Capacitors in Series (same Q on each plate): 1 / C_total = 1 / C₁ + 1 / C₂ + ... Inserting a dielectric material of relative permittivity ε_r > 1 polarises its molecules, creating an opposing internal electric field that increases capacitance (C = ε_r ε₀ A / d). If isolated (Q constant), V drops and E_stored = ½Q²/C decreases; if connected to a battery (V constant), Q increases and E_stored = ½CV² increases. |  |  |
| 7 | How do you propagate fractional/percentage uncertainties for powers and products in IB Physics Topic A (Data Booklet rules)? | If y = a ± b, absolute uncertainties add: Δy = Δa + Δb. If y = (a × b) / c, fractional uncertainties add: Δy / y = Δa / a + Δb / b + Δc / c. If y = a^n, fractional uncertainty is multiplied by \|n\|: Δy / y = \|n\| (Δa / a) (e.g., for period squared T², % uncertainty = 2 × %ΔT; for √L, % uncertainty = ½ × %ΔL). |  |  |
| 8 | Compare the roles of the Moderator, Control Rods, Heat Exchanger, and Shielding inside a pressurized water Nuclear Fission Reactor (E.4). | 1) Moderator (water, heavy water D2O, or graphite): slows down fast fission neutrons (~2 MeV) via elastic collisions to thermal energies (~0.025 eV) so they have a high cross-section for capture by Uranium-235 nuclei (without absorbing them). 2) Control Rods (boron or cadmium): raised or lowered into the reactor core to absorb excess neutrons and keep the reaction self-sustaining at criticality (1 neutron per fission triggers 1 further fission). 3) Heat Exchanger: transfers thermal energy from the pressurized primary coolant loop to boil water into high-pressure steam for turbines. |  |  |
| 9 | Derive the Orbital Speed (v_orb), Escape Speed (v_esc), and Total Mechanical Energy of an orbiting satellite of mass m at radius r around planet M (HL D.1). | 1) Orbital speed: equate gravitational force to centripetal force (GMm / r² = mv² / r) → v_orb = √(GM / r), so Kinetic Energy Ek = ½mv² = +GMm / (2r). 2) Gravitational Potential Energy: Ep = −GMm / r. 3) Total Mechanical Energy: E_total = Ek + Ep = +GMm/(2r) − GMm/r = −GMm / (2r) (if atmospheric drag reduces E_total, orbital radius r decreases and speed v_orb actually INCREASES!). 4) Escape speed (where Ek + Ep = 0 at infinity): ½mv_esc² − GMm/R = 0 → v_esc = √(2GM / R) = √2 v_orb. |  |  |
| 10 | Explain Stellar Parallax (d in parsecs = 1 / p in arcseconds) and why standard candles (Cepheid variables and Type Ia supernovae) are used for greater cosmic distances. | As Earth orbits the Sun (baseline = 1 AU), nearby stars shift against background stars by parallax angle p (in arcseconds): distance in parsecs d(pc) = 1 / p(arcsec) (1 pc = 3.26 light-years = 3.09 × 10¹⁶ m). Above ~100–1,000 pc, p becomes too small to measure accurately. Astronomers then use Standard Candles of known luminosity L (Cepheid variables via their Period–Luminosity relationship, or Type Ia supernovae peaking at L ≈ 10¹⁰ L_☉ when a white dwarf exceeds the 1.4 M_☉ Chandrasekhar limit) and calculate distance from b = L / (4πd²). |  |  |
| 11 | In IB Wave Behaviour (Theme C), state the equations for Simple Harmonic Motion (SHM) displacement, velocity, acceleration, and kinetic/potential energy (SL & HL C.1). | Defining SHM equation: a = −ω²x, where angular frequency ω = 2π / T = 2πf. For x = x₀ sin(ωt + φ): Velocity v = ωx₀ cos(ωt + φ) = ±ω√(x₀² − x²). Total Mechanical Energy in SHM (constant with no damping): E_total = ½mω²x₀². Potential Energy at displacement x: Ep = ½mω²x² (parabola); Kinetic Energy: Ek = ½mω²(x₀² − x²). Under light damping, amplitude decays exponentially while period remains nearly constant; in forced oscillations, resonance occurs when driving frequency equals natural frequency (f_d = f₀). |  |  |
| 12 | State the IB Physics equations for Work Done (W), Elastic Potential Energy, Power (P = Fv), and Efficiency (A.3). | Work done by a constant force at angle θ to displacement: W = Fs cos θ. Elastic potential energy stored in a spring of constant k: E_H = ½k(Δx)². Mechanical power output of a force moving an object at constant velocity v: P = ΔW / Δt = Fv. Efficiency: η = E_useful / E_total = P_useful / P_total. |  |  |
| 13 | How do you read a Minkowski Spacetime Diagram (ct vs x) and use the Spacetime Interval Invariant in HL Special Relativity (A.5)? | On a spacetime diagram (vertical axis = ct, horizontal axis = x): light worldlines always have gradient ±1 (angle 45°), and the worldline of an object moving at speed v has gradient = c / v = 1 / tan θ (where tan θ = v / c; the moving frame's x' and ct' axes scissor symmetrically towards the 45° light line by angle θ). Between any two events, the Spacetime Interval is invariant across all inertial frames: (Δs)² = (cΔt)² − (Δx)² = (cΔt')² − (Δx')². |  |  |
| 14 | In IB Astrophysics / Stellar Processes (E.5), explain Hydrostatic Equilibrium, the Proton–Proton Chain, the Hertzsprung–Russell (H–R) Diagram, and the Chandrasekhar & Oppenheimer–Volkoff Limits. | Main sequence stars are in hydrostatic equilibrium: inward gravitational pressure balances outward thermal/radiation pressure from core hydrogen fusion (p–p chain or CNO cycle; for main sequence stars, Luminosity L ∝ M^3.5). On the H–R Diagram (Luminosity vs Decreasing Surface Temperature OBAFGKM): Main Sequence runs diagonally from hot/luminous top-left to cool/dim bottom-right; Red Giants/Supergiants are top-right (cool but huge R in L = σ4πR²T⁴); White Dwarfs are bottom-left (hot but tiny R). Stellar remnants: if core remnant mass < 1.4 M_☉ (Chandrasekhar limit), electron degeneracy pressure halts collapse to form a White Dwarf; if 1.4 M_☉ < M_core < ~2.5–3 M_☉ (Oppenheimer–Volkoff limit), neutron degeneracy pressure forms a Neutron Star; above ~3 M_☉, it collapses into a Black Hole. |  |  |
| 15 | How do you linearize a power-law relationship y = a x^n or an exponential relationship y = a e^(bx) for IB Physics Paper 1B and Internal Assessment? | 1) Power law y = a x^n: take logs of both sides → log(y) = n log(x) + log(a). Plot log(y) on the vertical axis against log(x) on the horizontal axis to get a straight line with gradient = n and y-intercept = log(a). 2) Exponential relationship y = a e^(bx): take natural logs → ln(y) = bx + ln(a). Plot ln(y) against x to get a straight line with gradient = b and y-intercept = ln(a). |  |  |
| 16 | In IB Physics Theme D.3 & D.4, state the magnetic force on a current (F = BIL sin θ), on a moving charge (F = qvB sin θ), and Faraday's Law of Induction (HL). | Magnetic force on wire of length L carrying current I at angle θ to magnetic field B: F = BIL sin θ. Force on charge q moving at velocity v: F = qvB sin θ (circular radius r = mv / qB; in a velocity selector with crossed electric and magnetic fields, undeflected particles satisfy qE = qvB → v = E / B). Motional EMF induced in a straight rod of length L moving at speed v perpendicular to B: ε = BvL. Faraday's & Lenz's Law: ε = −N ΔΦ / Δt, where magnetic flux Φ = BA cos θ. |  |  |
| 17 | State the Phase Change and Phase Difference equations for travelling waves, and distinguish Refractive Index n₁ / n₂ = sin θ₂ / sin θ₁ = v₂ / v₁ = λ₂ / λ₁. | Phase difference Δφ (in radians) for path difference Δx: Δφ = (2π / λ) Δx. Constructive interference occurs when path difference Δx = nλ (Δφ = 2nπ); Destructive interference occurs when Δx = (n + ½)λ (Δφ = (2n + 1)π). When a wave refracts from medium 1 into medium 2, its frequency f stays CONSTANT while speed and wavelength change proportionally: n₁ / n₂ = sin θ₂ / sin θ₁ = v₂ / v₁ = λ₂ / λ₁. |  |  |
| 18 | Explain Radioactive Decay (N = N₀e^(−λt)), Why Beta-Minus Decay Produces a Continuous Energy Spectrum, and how Nuclear Binding Energy per Nucleon drives Fission and Fusion (E.3 & E.4). | In Alpha decay, emitted α particles have discrete energies because it is a 2-body decay. In Beta-minus decay (n → p + e⁻ + ν̄_e), the released decay energy is shared in variable proportions between three bodies (daughter nucleus, beta particle, and electron antineutrino ν̄_e), giving β⁻ particles a continuous energy spectrum up to a maximum endpoint energy (which led Pauli to postulate the neutrino). Activity A = λN = λN₀e^(−λt) with t₁/₂ = ln 2 / λ. |  |  |
| 19 | Explain Archimedes' Principle of Buoyancy (F_b = ρ_f V_f g) and Stokes' Law of Viscous Drag (F_d = 6πηrv) for a sphere falling at terminal velocity. | Archimedes' Buoyancy Force (upthrust) equals the weight of fluid displaced: F_b = ρ_fluid V_submerged g. Stokes' Law viscous drag on a small sphere of radius r moving slowly (laminar flow) through a fluid of viscosity η: F_d = 6πηrv. At terminal velocity v_t, downward weight balances upward buoyancy + viscous drag: mg = F_b + F_d → (4/3)πr³ρ_sphere g = (4/3)πr³ρ_fluid g + 6πηrv_t, so v_t = [2r²g(ρ_sphere − ρ_fluid)] / (9η). |  |  |
| 20 | State the two Postulates of Einstein's Special Relativity and the equations for Time Dilation and Length Contraction using the Lorentz Factor γ (HL A.5). | Postulates: 1) The laws of physics are identical in all inertial (non-accelerating) reference frames; 2) The speed of light in a vacuum (c = 3.00 × 10⁸ m s⁻¹) is constant for all inertial observers regardless of the motion of the source or observer. Lorentz factor: γ = 1 / √(1 − v²/c²) (always ≥ 1). Time Dilation: Δt = γ Δt₀ (where proper time Δt₀ is measured in the frame where the two events occur at the same spatial point—moving clocks run slow). Length Contraction: L = L₀ / γ (where proper length L₀ is measured at rest relative to the object—contracted only parallel to motion). Muon decay at Earth's surface confirms both. |  |  |
| 21 | Define Linear Impulse (J = FΔt = Δp) and distinguish between Elastic, Inelastic, and Totally Inelastic Collisions (IB Physics A.2). | Impulse J = F_net Δt = Δp (equal to the area under a Force–Time graph). In ALL isolated collisions (zero external resultant force), Total Linear Momentum is conserved (Σp_before = Σp_after). In an Elastic collision, Total Kinetic Energy is ALSO conserved (and relative speed of approach equals relative speed of separation). In an Inelastic collision, some kinetic energy is converted to thermal/sound/deformation energy (maximum Ek loss occurs when objects stick together in a totally inelastic collision). |  |  |
| 22 | Compare Gravitational Fields and Electrostatic Fields in IB Physics Theme D (SL & HL D.1 & D.2). | Gravitational (always attractive): Force F_g = Gm₁m₂ / r²; Field strength g = GM / r²; Potential V_g = −GM / r (J kg⁻¹); Potential energy Ep = mV_g = −GMm / r; Field strength equals negative potential gradient: g = −ΔV_g / Δr; Equipotential surfaces are perpendicular to field lines (zero work done moving along an equipotential: W = mΔV_g). Electrostatic (attractive or repulsive): F_e = kq₁q₂ / r² (k = 1 / 4πε₀ = 8.99 × 10⁹ N m² C⁻²); E = kQ / r²; V_e = kQ / r (V = J C⁻¹); E = −ΔV_e / Δr; Work done W = qΔV_e. |  |  |
| 23 | State Hubble's Law (v = H₀d), show how 1 / H₀ estimates the Age of the Universe, and state the two key observations supporting the Big Bang Model. | Hubble's Law: the recession speed v of a distant galaxy (found from cosmological redshift z = Δλ / λ₀ ≈ v / c) is directly proportional to its distance d: v = H₀d (where H₀ ≈ 70 km s⁻¹ Mpc⁻¹). Assuming constant expansion rate, Hubble Time (Age of the Universe) is T ≈ d / v = 1 / H₀ ≈ 13.8 billion years. Two pillars of the Big Bang: 1) Cosmological Redshift of galaxies (expansion of space itself: z = R / R₀ − 1); 2) Cosmic Microwave Background (CMB) radiation—isotropic black-body radiation at T = 2.73 K (λ_max ≈ 1.1 mm) left over from recombination. |  |  |
| 24 | How do you find the maximum and minimum gradients (uncertainty in slope and y-intercept) on a graph with error bars in IB Physics? | Draw the line of best fit through the data points. Then draw two worst-fit lines passing through all error bars: 1) Maximum gradient line (m_max): from the bottom of the first error bar to the top of the last error bar; 2) Minimum gradient line (m_min): from the top of the first error bar to the bottom of the last error bar. Uncertainty in gradient: Δm = (m_max − m_min) ÷ 2; Uncertainty in y-intercept: Δc = (c_max − c_min) ÷ 2. |  |  |
| 25 | State the equations for DC Circuits: Kirchhoff's Laws, Potential Divider, and Electric Cells with Internal Resistance (B.5). | Kirchhoff's First Law (conservation of charge at a junction): ΣI_in = ΣI_out. Kirchhoff's Second Law (conservation of energy around any closed loop): ΣV = 0 (sum of EMFs = sum of IR drops). Terminal voltage of a cell with EMF ε and internal resistance r: V = ε − Ir. Potential divider with resistors R₁ and R₂ in series across V_in: V_out (across R₂) = V_in × [R₂ / (R₁ + R₂)]. |  |  |
| 26 | State the four SUVAT equations and explain how air resistance (fluid drag) alters the trajectory of a projectile (IB Physics A.1). | SUVAT (constant acceleration only): 1) v = u + at; 2) s = ut + ½at²; 3) v² = u² + 2as; 4) s = ½(u + v)t. With air resistance (acting opposite to instantaneous velocity v): 1) Maximum height is LOWER; 2) Horizontal range is SHORTER; 3) Peak of trajectory is reached earlier in horizontal distance, and the descent path is steeper than the ascent (asymmetric trajectory). |  |  |
| 27 | State the Stefan–Boltzmann Law, Wien's Displacement Law, Albedo, and the Solar Constant in IB Thermal & Greenhouse Physics (B.1 & B.2). | Black-body radiation power: L = σAT⁴ (Stefan–Boltzmann constant σ = 5.67 × 10⁻⁸ W m⁻² K⁻⁴). Wien's Displacement Law: λ_max T = 2.9 × 10⁻³ m K (hotter stars peak at shorter, bluer wavelengths). Apparent brightness / Intensity at distance d: b = L / (4πd²) (at Earth's orbit, Solar Constant S ≈ 1360 W m⁻²; average incident intensity across Earth's spherical surface is S/4 ≈ 340 W m⁻²). Albedo α = Total scattered/reflected power ÷ Total incident power; Emissivity e = Power radiated by surface ÷ Power radiated by a black body of same A and T. |  |  |
| 28 | How do you determine the Half-Life of a short-lived vs a very long-lived radioactive isotope in IB Physics E.3? | 1) Short-lived isotope (minutes/hours): measure count rate with a Geiger–Müller (GM) tube, subtract the background count rate to get corrected activity A, and plot ln(A) against time t; the gradient equals −λ, and t₁/₂ = ln 2 / λ. 2) Extremely long-lived isotope (millions/billions of years, where activity appears constant over a lab session): measure the mass of the pure sample to find the number of nuclei N = (m / M_r) N_A, measure the corrected activity A, calculate λ = A / N, and then find t₁/₂ = ln 2 / λ. |  |  |
| 29 | State the HL Rotational Mechanics equations for Torque (τ), Moment of Inertia (I), Angular Momentum (L), and Rotational Kinetic Energy (A.4). | Rotational equivalents of linear mechanics: Angular kinematics: ω_f = ω_i + αt; θ = ω_i t + ½αt²; ω_f² = ω_i² + 2αθ (with v = ωr and a_t = αr). Torque: τ = Fr sin θ = Iα. Moment of Inertia: I = Σmr² (resistance to angular acceleration). Angular Momentum: L = Iω (conserved when net external torque τ_ext = 0, e.g., ice skater pulling arms in decreases I so ω increases, and ΔL = τΔt). Rotational Kinetic Energy: Ek_rot = ½Iω² = L² / (2I) (a rolling sphere/cylinder has total Ek = ½mv² + ½Iω²). |  |  |
| 30 | What happens to the phase of a wave upon reflection at a fixed boundary (or higher refractive index medium) vs a free boundary? | When a mechanical wave reflects at a fixed boundary (or when light reflects off a medium of HIGHER refractive index n₂ > n₁), it undergoes a phase change of π radians (180° inversion, equivalent to a half-wavelength ½λ path difference). When a wave reflects at a free boundary (or off a medium of lower refractive index n₂ < n₁), there is zero phase change (0 rad). |  |  |
| 31 | Compare the three mechanisms of Thermal Energy Transfer: Conduction (Fourier's Law), Convection, and Radiation. | 1) Conduction: transfer of kinetic energy through lattice vibrations (phonons) and collisions of delocalised free electrons in metals without bulk movement of matter; rate of heat transfer through area A and thickness Δx is ΔQ / Δt = kA(ΔT / Δx), where k is thermal conductivity. 2) Convection: bulk movement of fluids driven by density differences (heated fluid expands, becomes less dense, and rises). 3) Thermal Radiation: electromagnetic infrared waves requiring no medium (L = eσAT⁴). |  |  |
| 32 | In IB Quantum & Nuclear Physics (Theme E), explain Rutherford's Closest Approach / Deviations, Compton Scattering, and Bohr's Angular Momentum Quantisation (HL E.1 & E.2). | 1) Rutherford Alpha Scattering: at closest head-on approach d to a gold nucleus (Z=79), initial kinetic energy Ek of the alpha particle (q = 2e) converts entirely to electrostatic potential energy: Ek = k(2e)(Ze) / d → estimates upper bound of nuclear radius (~10⁻¹⁴ m); deviations from Rutherford scattering at very high alpha energies occur because the alpha particle gets close enough (<10⁻¹⁵ m) for the attractive Strong Nuclear Force to act. 2) Bohr model quantisation condition (standing de Broglie electron wave around orbit 2πr = nλ): mvr = nh / (2π), giving E_n = −13.6 / n² eV for Hydrogen. 3) Compton Scattering (particle nature of photons): X-ray photon scatters off a stationary electron, losing energy and shifting to a longer wavelength: Δλ = λ' − λ = (h / m_e c)(1 − cos θ). |  |  |

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