AP Physics 2
AP Physics 2 is an algebra-based, introductory college-level physics course administered by the College Board as part of its Advanced Placement program, designed to cultivate students' understanding of physics through inquiry-based classroom study, hands-on activities, and laboratory investigations.[1] The course emphasizes key scientific practices, including creating representations of physical situations, applying mathematical routines to model physical phenomena, posing scientific questions, and constructing arguments based on evidence.[1] It serves as a full-year equivalent to a second-semester introductory algebra-based physics course at the college level, building upon foundational concepts from AP Physics 1 by exploring more advanced topics such as thermodynamics, electric forces and fields, electric circuits, magnetism and electromagnetism, geometric and physical optics, waves and sound, and modern physics.[2] The curriculum is structured into flexible units that allow educators to sequence content as needed, with a strong focus on systems, fields, force interactions, change over time, conservation laws, and wave phenomena, with units on thermodynamics, electric force, field, and potential, and electric circuits each comprising 15%–18% of the multiple-choice exam, and units on magnetism and electromagnetism, geometric optics, waves, sound, and physical optics, and modern physics each comprising 12%–15%.[1] Students engage in guided-inquiry laboratory work, maintaining portfolios or notebooks of investigations to develop experimental skills and evidence-based reasoning, which are essential for college-level science.[1] The AP Physics 2 exam, administered annually in May, assesses student mastery through a hybrid digital format featuring multiple-choice questions (50% of the score) that test conceptual understanding and problem-solving, and free-response questions (50%) that require experimental design, qualitative/quantitative analysis, and data interpretation, with updates planned for the May 2026 administration.[3] Successful performance on the exam, typically a score of 3 or higher, can earn students college credit or advanced placement at many institutions, depending on individual university policies.[4]Overview
Course Description
AP Physics 2: Algebra-Based is an introductory college-level physics course that uses algebra and basic trigonometry to explore fundamental concepts in physics, equivalent to the second semester of a two-semester algebra-based university physics sequence.[5] The course builds on the foundational mechanics covered in AP Physics 1, extending students' understanding to more advanced topics through a structured framework of seven units.[5] The pedagogical approach emphasizes inquiry-based learning, where students engage in hands-on investigations to develop conceptual understanding, apply physical principles, and refine scientific practices such as experimental design, data analysis, and argumentation from evidence.[5] Approximately 25% of instructional time is dedicated to laboratory work, fostering skills in quantitative analysis and model-building using everyday equipment or more advanced tools.[5] This full-year course, typically spanning an academic year, aligns with expectations for introductory college physics by promoting deep comprehension over rote memorization.[5] The curriculum covers thermodynamics, electric force, field, and potential; electric circuits; magnetism and electromagnetism; geometric and physical optics; waves and sound; and modern physics, with exam weightings distributed across these units to reflect their relative emphasis.[5] Notably, the course previously included a dedicated unit on fluid statics and dynamics, but effective for the 2024–2025 school year, this content was transferred to AP Physics 1 to better balance the two courses.[6]Prerequisites
Successful completion of AP Physics 1 or an equivalent introductory high school physics course is strongly recommended for students enrolling in AP Physics 2, as it provides the foundational knowledge necessary for the course's advanced topics.[7][5] Proficiency in algebra, including solving equations, graphing, and working with vectors, along with basic trigonometry, is essential; completion of or concurrent enrollment in precalculus is also recommended but not strictly required.[7][5] Students should have familiarity with key concepts from AP Physics 1, such as kinematics, dynamics, work, energy, and power; linear momentum; torque and rotational motion.[8][9] This background assumes an understanding of Newtonian mechanics as a foundation for the thermodynamics and electromagnetism explored in AP Physics 2, building on fluid dynamics covered in AP Physics 1.[5] In addition, prior experience with laboratory skills is important, including data collection through observation and measurement, data analysis using graphical and mathematical techniques, and experimental design to test hypotheses.[5][1] Mathematical competencies required include unit conversions, adherence to significant figures, and basic statistical methods for error analysis in experimental results.[5][10]History
Introduction and Redesign
AP Physics 2 was introduced by the College Board in the 2014-15 school year as part of a major redesign of its Advanced Placement physics offerings, specifically to replace the longstanding AP Physics B exam.[1] AP Physics B, which had been administered from the 1950s until 2014, encompassed a broad survey of introductory physics topics including mechanics, electricity and magnetism, waves, optics, and modern physics, all within a single year-long algebra-based course.[1] However, it faced significant criticism for its superficial coverage and lack of rigor, as an in-depth study by the National Research Council in 2002 described it as a "gigantic course" that encouraged cursory treatment of topics, prioritizing breadth over deep conceptual understanding and failing to align closely with college-level expectations.[11] The redesign addressed these shortcomings by dividing the content of AP Physics B into two separate year-long courses: AP Physics 1, focused primarily on Newtonian mechanics, and AP Physics 2, which covers more advanced topics such as fluids, thermodynamics, electricity and magnetism, optics, and modern physics.[1] This split aimed to provide greater depth in each area, better mirroring the typical two-semester sequence of introductory college physics courses and ultimately improving student preparation and outcomes for postsecondary success.[12] The development process involved collaborative committees comprising college faculty, experienced high school AP teachers, and input from physics education experts, including representatives from organizations like the American Association of Physics Teachers (AAPT).[12] Key goals included shifting toward inquiry-based learning through hands-on labs and scientific practices, while reducing emphasis on rote memorization and formulaic problem-solving to foster genuine conceptual mastery.[1] The inaugural AP Physics 2 exam was administered in May 2015, marking the first full implementation of the redesigned curriculum.[1] Early administration revealed challenges stemming from the increased difficulty and depth, with a pass rate of approximately 55.7% (scores of 3 or higher) compared to about 61% for AP Physics B in 2014, reflecting the steeper demands on students transitioning to the new format.[13]Recent Updates
In response to feedback from educators and alignment with introductory college-level curricula, the College Board implemented significant revisions to AP Physics 2 effective fall 2024 for the May 2025 exam, building on the principles of the 2014 redesign by further streamlining content to emphasize conceptual understanding.[5] These updates addressed early post-redesign challenges in the algebra-based courses, including low pass rates for a score of 3 or higher in AP Physics 1 that hovered around 35-40% in the initial years (e.g., 39.3% in 2015), while AP Physics 2 maintained higher rates of 55-65%; the revisions aimed to balance loads and deepen exploration of core topics.[14][6] A key structural change involved relocating the entire Fluids unit from AP Physics 2 to AP Physics 1 to balance course loads between the two algebra-based physics courses and improve logical sequencing, as fluids concepts build on Newtonian mechanics covered in Physics 1.[5][6] This shift freed up instructional time in AP Physics 2, enabling enhanced coverage of remaining units, particularly Waves and Optics, which were split into two distinct units—Geometric Optics and Waves, Sound, and Physical Optics—for more focused and in-depth treatment of topics like interference, diffraction, and the Doppler effect.[5] The exam format was unified across all four AP Physics courses to promote consistency and reduce administrative complexity, shortening the total exam time to 3 hours with approximately 40 multiple-choice questions and 4 free-response questions; notably, multi-select multiple-choice questions were eliminated in AP Physics 2 to streamline assessment of foundational skills.[15][16] Clarifications to the Course and Exam Description (CED) were released in fall 2024 to better align with college curricula, including minor refinements to sample free-response questions for clearer scaffolding and accessibility in digital testing formats, alongside updated guidance on lab expectations to emphasize inquiry-based investigations without altering core learning objectives.[17][15] The May 2025 AP Physics 2 exam, the first under these revisions, resulted in a pass rate of 72.6% (scores of 3 or higher), demonstrating continued improvement in student outcomes.[18] The College Board continues to conduct periodic reviews through expert committees, incorporating teacher and higher education feedback; as of November 2025, no major overhauls beyond these 2024-2025 revisions are planned.[15]Curriculum
Thermodynamics
The thermodynamics unit in AP Physics 2 examines the behavior of thermal energy in physical systems, building on the conservation of energy principle from prerequisite courses to analyze heat transfer, work, and internal energy changes.[5] Students explore how macroscopic properties like pressure, volume, and temperature relate to microscopic particle motion, emphasizing qualitative and quantitative models for processes in ideal gases and other systems.[5] This unit, comprising 15–18% of the exam, integrates science practices such as deriving equations from kinetic theory and interpreting PV diagrams to represent thermodynamic paths.[5] Kinetic molecular theory forms the foundation, positing that gases consist of many particles in constant, random motion with elastic collisions, negligible particle volume compared to container volume, and no intermolecular forces except during collisions.[5] These assumptions define an ideal gas, where temperature corresponds to the average kinetic energy of the particles, given by KE_{avg} = \frac{3}{2} kT, with k as Boltzmann's constant and T as absolute temperature in kelvin.[5] From this theory, the root-mean-square speed of particles is v_{rms} = \sqrt{\frac{3kT}{m}}, where m is the particle mass, linking microscopic motion to observable pressure via momentum transfer during wall collisions.[5] Thermal equilibrium occurs when systems reach the same temperature, with no net heat flow between them.[5] The ideal gas law, PV = nRT (or PV = NkT for N particles), quantifies the relationship among pressure P, volume V, number of moles n (or particles N), gas constant R (or Boltzmann's constant k), and temperature T.[5] Derived from kinetic molecular theory by equating pressure from particle collisions to macroscopic measurements, it applies under ideal conditions of low density and high temperature.[5] For isothermal processes (constant T), the law implies PV = constant, as volume inversely varies with pressure while internal energy remains unchanged for ideal gases.[5] In isobaric processes (constant P), V \propto T, allowing derivations of volume changes with temperature at fixed pressure.[5] Thermal expansion describes how materials change dimensions with temperature due to increased particle vibrations.[5] For linear expansion, the change in length is \Delta L = \alpha L_0 \Delta T, where \alpha is the coefficient of linear expansion, L_0 the initial length, and \Delta T the temperature change; volumetric expansion follows \Delta V = \beta V_0 \Delta T with \beta \approx 3\alpha.[5] Specific heat capacity quantifies the heat Q needed to raise the temperature of mass m by \Delta T, via Q = mc \Delta T, where c is the specific heat, independent of the temperature interval for most substances.[5] Calorimetry applies this in isolated systems where heat lost by one object equals heat gained by another, incorporating phase changes through latent heat Q = mL, with L_f for fusion (melting/freezing) and L_v for vaporization (boiling/condensation).[5] During phase changes at constant temperature, energy alters molecular potential energy without temperature rise, as seen in PV diagrams where horizontal lines represent isobaric phase transitions.[5] The first law of thermodynamics expresses energy conservation for a system: \Delta U = Q - W, where \Delta U is the change in internal energy, Q is heat added to the system (positive if absorbed), and W is work done by the system (positive for expansion).[5] For an ideal monatomic gas, internal energy depends only on temperature, U = \frac{3}{2} nRT, so \Delta U = \frac{3}{2} nR \Delta T, independent of volume or pressure changes.[5] Work in volume changes is W = P \Delta V for isobaric processes or \int P \, dV generally, visualized on PV diagrams where area under the curve represents work.[5] Isothermal processes on PV diagrams follow hyperbolas (PV = constant), adiabatic processes (no heat exchange) obey PV^\gamma = constant with \gamma = C_p / C_v (ratio of specific heats), isobaric lines are horizontal, and isochoric (constant volume) are vertical.[5] The second law states that entropy, a measure of disorder, increases in spontaneous processes within an isolated system, implying heat flows naturally from hot to cold bodies and no process can convert heat entirely to work without waste.[5] For reversible processes at constant temperature, entropy change is \Delta S = \frac{Q}{T}, with total entropy unchanging in reversible cycles but increasing overall in irreversible ones.[5] Heat engines convert heat Q_h from a hot reservoir to work W, exhausting Q_c to a cold reservoir, with efficiency \eta = W / Q_h = 1 - Q_c / Q_h.[5] The Carnot cycle, an ideal reversible engine, achieves maximum efficiency \eta = 1 - \frac{T_c}{T_h}, where T_h and T_c are hot and cold reservoir temperatures in kelvin, setting the theoretical limit for real engines.[5]Electric Force, Field, and Potential
Electric charge is a fundamental property of matter that comes in two types: positive and negative. The law of conservation of charge states that the total electric charge in an isolated system remains constant, as charge cannot be created or destroyed, only transferred. Charge is also quantized, meaning it occurs in discrete packets that are integer multiples of the elementary charge e = 1.602 \times 10^{-19} C, a principle experimentally verified by Robert Millikan's oil-drop experiment in 1909./University_Physics_II_-Thermodynamics_Electricity_and_Magnetism(OpenStax)/06%3A_Gauss's_Law/6.02%3A_The_Electric_Field) In the AP Physics 2 curriculum, students explore these properties to understand charge interactions in electrostatic systems.[5] The interaction between point charges is governed by Coulomb's law, which quantifies the electrostatic force \mathbf{F} between two charges q_1 and q_2 separated by a distance r: \mathbf{F} = k \frac{q_1 q_2}{r^2} \hat{r} where k = 8.99 \times 10^9 Nm²/C² is Coulomb's constant, and the force is repulsive for like charges and attractive for unlike charges. This inverse-square law, first experimentally established by Charles-Augustin de Coulomb in 1785, describes the magnitude and direction of the force along the line joining the charges./18%3A_Electric_Charge_and_Electric_Field/18.03%3A_Coulombs_Law) In AP Physics 2, calculations using this law are limited to systems with up to four point charges, emphasizing vector addition for net forces.[5] The electric field \mathbf{E} provides a vector description of the electrostatic influence at a point in space, defined as the force per unit positive test charge: \mathbf{E} = \frac{\mathbf{F}}{q_0} where q_0 is a small positive test charge that does not disturb the field. For a single point charge q, the electric field at distance r is \mathbf{E} = k \frac{q}{r^2} \hat{r}. This field points away from positive charges and toward negative charges. Uniform electric fields, such as those between parallel charged plates, have constant magnitude and direction, with E = \sigma / \epsilon_0 where \sigma is the surface charge density and \epsilon_0 = 8.85 \times 10^{-12} C²/Nm² is the vacuum permittivity./University_Physics_II_-Thermodynamics_Electricity_and_Magnetism(OpenStax)/06%3A_Gauss's_Law/6.03%3A_Electric_Field) AP Physics 2 students calculate fields from point charges and apply superposition for multiple charges.[5] Electric field lines visualize the field's direction and strength, originating from positive charges and terminating on negative charges, with density proportional to field magnitude; lines never cross and are perpendicular to equipotential surfaces. The superposition principle states that the net electric field from multiple charges is the vector sum of individual fields, allowing complex configurations to be analyzed by adding contributions linearly. This principle, fundamental to electrostatics, enables predictions of field patterns in charge distributions./University_Physics_II_-Thermodynamics_Electricity_and_Magnetism(OpenStax)/06%3A_Gauss's_Law/6.03%3A_Electric_Field) In the AP curriculum, students use these concepts to sketch field lines and compute net fields for systems of two to four charges.[5] Electric potential energy U for two point charges is the work required to assemble them from infinite separation: U = k \frac{q_1 q_2}{r}. Positive for like charges (repulsive) and negative for unlike charges (attractive), this scalar quantity depends on charge signs and separation. The electric potential V at a point due to a charge q is the potential energy per unit charge: V = \frac{U}{q_0} = k \frac{q}{r}, measured relative to infinity where V = 0. For multiple charges, potentials superpose algebraically as scalars. These concepts build on energy conservation, linking electrostatics to mechanical prerequisites./University_Physics_II_-Thermodynamics_Electricity_and_Magnetism(OpenStax)/07%3A_Electric_Potential/7.02%3A_Electric_Potential_Energy) AP Physics 2 emphasizes calculations for systems with limited charges, focusing on conceptual energy changes.[5] The potential difference \Delta V between two points is the work per unit charge to move a test charge along a path: \Delta V = -\int_a^b \mathbf{E} \cdot d\mathbf{l}, negative because the field points toward decreasing potential. For uniform fields, this simplifies to \Delta V = E d, where d is the perpendicular distance. Equipotential surfaces are perpendicular to field lines, forming regions of constant potential where no work is done on charges moving along them. In AP Physics 2, students derive these relations and apply them to uniform fields and point charge systems./University_Physics_II_-Thermodynamics_Electricity_and_Magnetism(OpenStax)/07%3A_Electric_Potential/7.03%3A_Electric_Potential_and_Potential_Difference) In electrostatic equilibrium, conductors exhibit unique charge behaviors: excess charge resides on the surface, with free electrons redistributing until the internal electric field is zero. The surface charge density is higher at sharper points, influencing field strength nearby. Electrostatic shielding occurs as induced charges on a conductor's surface cancel external fields inside cavities or the conductor itself, protecting enclosed regions from external influences. These properties, derived from Gauss's law applications, are key to understanding Faraday cages and conductor behavior in AP Physics 2./University_Physics_II_-Thermodynamics_Electricity_and_Magnetism(OpenStax)/06%3A_Gauss's_Law/6.05%3A_Conductors_in_Electrostatic_Equilibrium)[5]Electric Circuits
In AP Physics 2, the Electric Circuits unit explores the behavior of direct current (DC) circuits, emphasizing steady-state analysis with resistors and batteries, as well as transient phenomena in circuits involving capacitors. Students learn to model circuits using schematic diagrams and apply conservation principles to predict currents, voltages, and energy transfers. This unit builds on electric potential by applying potential differences to drive charge flow in conductive paths.[5] Electric current is defined as the rate at which charge flows through a conductor, given by the equation I = \frac{\Delta q}{\Delta t}, where I is current in amperes (A), \Delta q is the change in charge in coulombs (C), and \Delta t is the time interval in seconds (s). In circuits, current represents the net flow of positive charge from higher to lower electric potential, conserving charge at junctions. Resistance opposes current flow in a conductor and depends on the material's resistivity \rho, the length L, and the cross-sectional area A, according to R = \frac{\rho L}{A}, where R is resistance in ohms (\Omega). Materials like copper have low resistivity (approximately $1.7 \times 10^{-8} , \Omega \cdot \mathrm{m}$ at room temperature), making them suitable for wires.[19][20][5] Ohm's law relates voltage V, current I, and resistance R in ohmic devices via V = IR, indicating that current is directly proportional to the potential difference across a resistor at constant temperature. This linear relationship holds for many conductors but not for non-ohmic elements like diodes. For example, a 10 \Omega resistor with a 5 V potential difference carries 0.5 A of current. Power dissipation in resistors, representing the rate of energy conversion to heat, is expressed as P = IV = I^2 R = \frac{V^2}{R}, with units in watts (W). A 100 W bulb on a 120 V line draws about 0.83 A, illustrating efficient energy use in household circuits.[21][22][19][5] In series networks, resistors share the same current, yielding an equivalent resistance R_\mathrm{eq} = R_1 + R_2 + \cdots + R_n, which increases total opposition to flow. For parallel networks, the voltage is the same across branches, so \frac{1}{R_\mathrm{eq}} = \frac{1}{R_1} + \frac{1}{R_2} + \cdots + \frac{1}{R_n}, reducing overall resistance and allowing higher total current. For instance, two 6 \Omega resistors in series equivalent 12 \Omega, while in parallel they equivalent 3 \Omega. Complex circuits combine these configurations, requiring step-by-step reduction to a single equivalent resistance for analysis.[23][24][5] Kirchhoff's junction rule, based on charge conservation, states that the algebraic sum of currents at any junction is zero: \sum I = 0, with incoming currents positive and outgoing negative. Kirchhoff's loop rule, from energy conservation, requires the sum of potential differences around any closed loop to be zero: \sum V = 0. These rules enable solving for unknowns in multi-branch circuits; for example, in a loop with a 12 V battery and two resistors, the voltage drops must balance the battery's emf. Students apply these alongside Ohm's law to derive currents and voltages systematically.[25][5] Capacitors store charge and energy in electric circuits, with capacitance C for a parallel-plate device given by C = \frac{Q}{V} = \frac{\epsilon_0 A}{d}, where \epsilon_0 = 8.85 \times 10^{-12} \, \mathrm{F/m} is the permittivity of free space, A is plate area, and d is separation. The stored energy is U = \frac{1}{2} Q V = \frac{1}{2} C V^2, representing work done to separate charges against their mutual attraction. In steady-state DC circuits, capacitors act as open circuits once charged, blocking current.[26][27][5] RC circuits exhibit transient behavior during charging or discharging, characterized by the time constant \tau = RC, which sets the scale for how quickly the capacitor reaches steady state (about 5\tau for near-full charge). For charging from a battery of emf \mathcal{E}, the charge on the capacitor is q(t) = Q (1 - e^{-t/\tau}), where Q = C \mathcal{E} is the maximum charge, approaching Q asymptotically. Discharging through a resistor follows q(t) = Q e^{-t/\tau}, with current i(t) = \frac{q(t)}{R}. Graphs of q(t) versus t show exponential curves, emphasizing that current decreases as the capacitor charges.[28][5] Ammeters measure current by being placed in series, ideally with zero internal resistance to avoid altering the circuit; real ammeters use low-resistance shunts. Voltmeters measure potential difference in parallel, requiring high internal resistance (often $10 \, \mathrm{M}\Omega) to draw negligible current. Batteries have internal resistance r, modeled as an ideal emf \mathcal{E} in series with r, so terminal voltage V = \mathcal{E} - Ir under load, dropping from the open-circuit value. For a 1.5 V battery with r = 0.1 \, \Omega supplying 1 A, V = 1.4 V. These concepts highlight practical measurement limitations and real-world deviations from ideal components.[29][5]Magnetism and Electromagnetism
In AP Physics 2, the Magnetism and Electromagnetism unit explores the interactions between magnetic fields and charged particles or currents, as well as the principles of electromagnetic induction that link changing magnetic fields to electric effects. This unit, comprising 12–15% of the exam, builds on prior knowledge of electric circuits by incorporating magnetic influences on currents, emphasizing conceptual understanding of field behaviors, forces, and induced electromotive forces (EMFs). Students learn to apply vector-based calculations and qualitative rules to predict directions and magnitudes, with practical applications like generators and transformers illustrating energy transfer.[5] The magnetic force on a moving charged particle is given by \vec{F} = q \vec{v} \times \vec{B}, where the magnitude is F = q v B \sin \theta, with \theta the angle between the velocity \vec{v} and magnetic field \vec{B}. This force is always perpendicular to both \vec{v} and \vec{B}, causing circular or helical paths for charged particles without changing their speed. The direction is determined by the right-hand rule: fingers in the direction of \vec{v}, palm facing \vec{B}, thumb points to \vec{F} for positive charges. For a current-carrying wire, the force is \vec{F} = I \vec{L} \times \vec{B}, with magnitude F = I L B \sin \theta, where L is the wire length and I the current; this arises from the collective forces on individual charge carriers.[5][30] Magnetic fields originate from moving charges and currents, with no isolated monopoles—fields form closed loops around sources. For a long straight wire carrying current I, the magnetic field at distance r is B = \frac{\mu_0 I}{2\pi r}, circling the wire according to the right-hand rule (thumb along I, fingers curl in \vec{B} direction). Inside a solenoid—a coil of n turns per unit length carrying I—the uniform field is B = \mu_0 n I, approximating an ideal solenoid with tightly wound turns and negligible end effects. The Earth's magnetic field, approximately 25–65 μT at the surface, acts like a bar magnet's dipole field, influencing compass needles and providing context for geomagnetic phenomena. The Biot-Savart law provides a general method to calculate fields from current elements: d\vec{B} = \frac{\mu_0}{4\pi} \frac{I d\vec{l} \times \hat{r}}{r^2}, integrating over the current path for complex geometries. Ampère's law, \oint \vec{B} \cdot d\vec{l} = \mu_0 I_{\rm enc}, simplifies calculations for symmetric sources like wires or solenoids by relating field circulation to enclosed current. Maxwell's addition includes displacement current, \mu_0 \epsilon_0 \frac{d\Phi_E}{dt}, accounting for changing electric fields as a magnetic field source, ensuring consistency in electromagnetic wave propagation.[5][31][32][33] Electromagnetic induction occurs when a changing magnetic flux \Phi_B = \int \vec{B} \cdot d\vec{A} induces an EMF, quantified by Faraday's law: \mathcal{E} = -\frac{d\Phi_B}{dt}. For N loops, it generalizes to \mathcal{E} = -N \frac{d\Phi_B}{dt}. Lenz's law specifies the direction: the induced current creates a magnetic field opposing the flux change, conserving energy by resisting the cause. Motional EMF arises when a conductor of length L moves at velocity v perpendicular to \vec{B}, yielding \mathcal{E} = B L v, as charges experience the Lorentz force separating them across the conductor. In transformers, two coils share a magnetic core; the voltage ratio follows \frac{V_s}{V_p} = \frac{N_s}{N_p}, where subscripts denote secondary and primary, enabling efficient AC voltage stepping without direct connection, assuming ideal conditions with no energy loss. These concepts unify electricity and magnetism, foreshadowing electromagnetic waves.[5][34][35]Geometric Optics
Geometric optics in AP Physics 2 employs the ray approximation to model light propagation, treating light as straight-line rays that interact with optical elements like mirrors and lenses through reflection and refraction, which is valid when wavelengths are much smaller than the scales of interest.[5] This approach simplifies analysis of image formation without considering wave phenomena such as interference or diffraction. Light rays originate from point sources and travel in straight lines until encountering a boundary or optical device.[36] Reflection occurs when light rays encounter a surface and bounce off according to the law of reflection, which states that the angle of incidence equals the angle of reflection, with both angles measured relative to the normal at the point of incidence.[36] For plane mirrors, images are virtual, upright, and the same size as the object, appearing at the same distance behind the mirror as the object is in front.[5] Spherical mirrors, either concave or convex, have a focal length f = R/2, where R is the radius of curvature (positive for concave, negative for convex).[36] The mirror equation relates object distance d_o, image distance d_i, and focal length: \frac{1}{f} = \frac{1}{d_o} + \frac{1}{d_i}, with magnification m = -\frac{d_i}{d_o}, where a negative m indicates an inverted image.[5] Concave mirrors can form real, inverted images for objects beyond the focal point, while convex mirrors always produce virtual, upright, diminished images.[36] Refraction describes the bending of light rays at the interface between two media due to a change in speed, governed by Snell's law: n_1 \sin \theta_1 = n_2 \sin \theta_2, where n is the index of refraction and \theta the angle from the normal.[36] The index of refraction n for a medium is defined as n = c / v, with c the speed of light in vacuum and v the speed in the medium; for example, n \approx 1.33 for water and n \approx 1.50 for glass./25:_Geometric_Optics/25.03:_The_Law_of_Refraction) When light travels from a higher-n medium to a lower-n one, total internal reflection can occur if the angle of incidence exceeds the critical angle \theta_c, where \sin \theta_c = n_2 / n_1.[5] This phenomenon is exploited in optical fibers and prisms.[36] Thin lenses, converging (convex) or diverging (concave), focus light using the lensmaker's equation for focal length in air: \frac{1}{f} = (n - 1) \left( \frac{1}{R_1} - \frac{1}{R_2} \right), where n is the lens material's index, and R_1, R_2 are the radii of curvature (sign convention: positive if the center is to the right of the surface for light from the left).[36] The thin lens equation mirrors the mirror equation: \frac{1}{f} = \frac{1}{d_o} + \frac{1}{d_i}, with the same magnification formula.[5] Converging lenses form real, inverted images for distant objects and virtual, upright images for nearby ones, while diverging lenses always yield virtual, upright, diminished images.[36] Combinations of lenses or mirrors are analyzed sequentially using these equations, adjusting object and image distances for each element.[5] Image formation in geometric optics is characterized by whether images are real (formed by converging rays, projectable on a screen) or virtual (formed by diverging rays, appearing to emanate from behind the optic), and by orientation (upright or inverted) and size (magnified or reduced), determined via ray diagrams or equations.[5] For mirrors and lenses, ray diagrams typically trace two or three principal rays: parallel to the axis (passes through focal point after reflection/refraction), through the center (undeviated), and through the focal point (emerges parallel).[36] These characteristics depend on object position relative to focal points and the optic type, enabling predictions of image location and properties in systems like cameras or microscopes.[5]| Image Type | Formation | Orientation | Example |
|---|---|---|---|
| Real | Converging rays on same side as incoming light | Inverted | Concave mirror, object beyond focal point; converging lens, object beyond focal point[36] |
| Virtual | Diverging rays, appears opposite side | Upright | Plane mirror; convex mirror; converging lens, object inside focal point; diverging lens[36] |
Waves, Sound, and Physical Optics
In AP Physics 2, the study of waves, sound, and physical optics builds on the principles of mechanical and electromagnetic wave propagation, emphasizing how waves transfer energy through media without net displacement of matter.[5] Waves are classified as transverse, where particle displacement is perpendicular to the direction of propagation (e.g., waves on a string), or longitudinal, where displacement is parallel to propagation (e.g., sound waves in air)./Book%3A_University_Physics_I_-Mechanics_Sound_Oscillations_and_Waves(OpenStax)/16%3A_Waves/16.01%3A_Traveling_Waves) The fundamental relationship governing periodic waves is the wave speed equation, v = f \lambda, where v is the speed, f is the frequency, and \lambda is the wavelength; this holds for both mechanical and electromagnetic waves in uniform media. Superposition occurs when two or more waves overlap, resulting in constructive interference (amplitudes add) or destructive interference (amplitudes subtract), a principle central to understanding complex wave behaviors./Book%3A_University_Physics_I_-Mechanics_Sound_Oscillations_and_Waves(OpenStax)/16%3A_Waves/16.11%3A_The_Principle_of_Superposition) Standing waves form from the interference of incident and reflected waves on a fixed medium, producing nodes (zero displacement) and antinodes (maximum displacement), with harmonics determined by boundary conditions such as fixed ends on a string.[5] Sound waves, as longitudinal mechanical waves, propagate through elastic media like air, with speed depending on the medium's properties; for example, the speed in air is approximately 343 m/s at room temperature, increasing in denser media like water due to stronger restoring forces. The intensity I of a spherical sound wave decreases with distance as I \propto \frac{1}{r^2}, reflecting the conservation of energy over an expanding wavefront area./Book%3A_University_Physics_I_-Mechanics_Sound_Oscillations_and_Waves(OpenStax)/17%3A_Sound/17.03%3A_Sound_Intensity_and_Intensity_Level) Sound intensity level is quantified in decibels using \beta = 10 \log \left( \frac{I}{I_0} \right), where I_0 = 1.0 \times 10^{-12} W/m² is the reference intensity at the threshold of hearing; this logarithmic scale accounts for the human ear's nonlinear perception of loudness. The Doppler effect for sound describes the observed frequency shift due to relative motion, given by f' = f \frac{v \pm v_o}{v \pm v_s}, where v is the speed of sound, v_o is the observer's speed (positive toward the source), and v_s is the source's speed (positive away from the observer); approaching objects produce higher frequencies, explaining phenomena like siren pitch changes./Book%3A_University_Physics_I_-Mechanics_Sound_Oscillations_and_Waves(OpenStax)/17%3A_Sound/17.08%3A_The_Doppler_Effect) Interference patterns arise from the superposition of coherent waves, demonstrating wave nature in both sound and light. In Young's double-slit experiment with light, bright fringes (maxima) occur where the path difference is an integer multiple of the wavelength, satisfying d \sin \theta = m \lambda, with d as slit separation, \theta the angle from the central maximum, m the order (integer), and \lambda the wavelength; this setup confirms light's wave properties through observable fringe spacing.[37] Thin-film interference, seen in soap bubbles or oil slicks, results from phase shifts upon reflection at boundaries with different refractive indices, leading to constructive interference for condition $2nt \cos \theta = m \lambda, where n is the film's refractive index, t its thickness, and \theta the angle of incidence; destructive interference occurs for half-integer multiples, producing color patterns. Diffraction describes the bending and spreading of waves around obstacles or through apertures, most pronounced when the aperture size is comparable to the wavelength. For single-slit diffraction of light, minima occur at w \sin \theta = m \lambda, where w is the slit width and m = \pm 1, \pm 2, \dots; the central maximum widens as w decreases, blurring sharp geometric images./University_Physics_III_-Optics_and_Modern_Physics(OpenStax)/04%3A_Diffraction/4.02%3A_Single-Slit_Diffraction) Diffraction gratings, with many closely spaced slits, produce sharp maxima at d \sin \theta = m \lambda, where d is the slit spacing; these are used in spectrometers to disperse light by wavelength for analysis. Polarization applies to transverse waves like electromagnetic radiation, where oscillations are confined to a plane; unpolarized light from sources like the sun has random orientations, while polarizers transmit only one direction. Malus's law quantifies transmitted intensity through a polarizer as I = I_{\max} \cos^2 \theta, with \theta the angle between the polarization direction and the polarizer's axis; crossed polarizers (\theta = 90^\circ) block transmission entirely./Book%3A_University_Physics_III_-Optics_and_Modern_Physics(OpenStax)/01%3A_The_Nature_of_Light/1.11%3A_Polarization) Brewster's angle \theta_B, given by \tan \theta_B = n_2 / n_1 for light incident from medium 1 to 2, is the incidence angle where reflected light is fully polarized perpendicular to the plane of incidence, minimizing glare in applications like sunglasses. Physical optics addresses limitations of geometric optics approximations, which treat light as rays ignoring wave effects; these break down when wavelengths approach obstacle or aperture scales, leading to diffraction blurring edges or interference altering predicted paths, as quantified by the Fresnel number or Rayleigh criterion for resolution.[5] In AP Physics 2, this wave model explains unresolved phenomena in ray tracing, such as the spreading of light beams or spectral lines in gratings, bridging classical optics with broader wave principles./University_Physics_III_-Optics_and_Modern_Physics(OpenStax)/03%3A_Interference/3.01%3A_Youngs_Double-Slit_Experiment)Modern Physics
The Modern Physics unit in AP Physics 2 explores foundational 20th-century concepts that extend beyond classical mechanics, emphasizing special relativity, quantum phenomena, and nuclear processes. These topics, comprising 12–15% of the exam, introduce students to the limitations of Newtonian physics and the probabilistic nature of subatomic scales, using algebraic manipulations and conceptual analysis.[5] Special relativity, formulated by Albert Einstein in 1905, establishes that the speed of light c is invariant and that physical laws are identical in all inertial frames. A key prediction is time dilation: for an object moving at velocity v relative to an observer, the observed time interval \Delta t relates to the proper time \Delta t_0 (measured in the object's rest frame) by \Delta t = \gamma \Delta t_0, where \gamma = \frac{1}{\sqrt{1 - \frac{v^2}{c^2}}}. This effect has been experimentally verified, such as in muon decay lifetimes extended when cosmic-ray muons travel near light speed. Length contraction complements this, shortening distances parallel to the motion: L = L_0 / \gamma, where L_0 is the proper length, observable in particle accelerator experiments. Einstein's framework culminates in mass-energy equivalence, E = mc^2, linking inertial mass m to rest energy, which underpins nuclear reactions and has been confirmed through pair production and annihilation processes. The photoelectric effect illustrates light's particle-like behavior, as Einstein explained in 1905 by treating electromagnetic radiation as discrete photons. When monochromatic light of frequency f strikes a metal surface, electrons are ejected only if f exceeds a threshold determined by the material's work function \phi; the maximum kinetic energy of photoelectrons is given by K_{\max} = hf - \phi, where h is Planck's constant. This equation predicts a linear relationship between stopping potential V_s (which halts electron emission) and frequency, eV_s = K_{\max}, verified by Millikan's 1916 experiments and central to technologies like photodetectors. The effect resolves classical wave theory's failure to explain instantaneous emission and intensity dependence solely on electron count, not energy per electron.[38][38] Niels Bohr's 1913 model of the hydrogen atom reconciles classical orbits with quantum stability by quantizing angular momentum in circular paths. Electrons occupy discrete energy levels E_n = -\frac{13.6 \, \text{eV}}{n^2}, where n is the principal quantum number; transitions between levels emit or absorb photons with energy \Delta E = h f, producing characteristic spectral lines like the Lyman, Balmer, and Paschen series. This quantized structure explains hydrogen's emission spectrum, where electron de-excitation from higher to lower n yields discrete wavelengths, as observed in discharge tube experiments, and laid groundwork for quantum mechanics despite its limitations for multi-electron atoms.[39][39] Wave-particle duality extends to matter, as proposed by Louis de Broglie in 1924, asserting that any particle with momentum p has an associated wavelength \lambda = h / p. This hypothesis, confirmed by electron diffraction experiments like Davisson-Germer in 1927, unifies light's dual nature (waves in interference, particles in Compton scattering) with matter's, evident in atomic electron waves stabilizing Bohr orbits. Complementing this, Werner Heisenberg's 1927 uncertainty principle quantifies measurement limits: \Delta x \Delta p \geq \hbar / 2, where \hbar = h / 2\pi, \Delta x is position uncertainty, and \Delta p is momentum uncertainty; it arises from non-commuting quantum observables and prohibits simultaneous precise knowledge of conjugate variables, as demonstrated in single-slit diffraction broadening position-momentum trade-offs./06%3A_Photons_and_Matter_Waves/6.06%3A_De_Broglies_Matter_Waves)/06%3A_Photons_and_Matter_Waves/6.06%3A_De_Broglies_Matter_Waves)[40] Nuclear physics in AP Physics 2 centers on stability and reactions, starting with the mass defect \Delta m = Z m_p + N m_n - M, where Z is the proton number, N the neutron number, m_p and m_n are nucleon masses, and M is the atomic mass; the binding energy B = \Delta m c^2 represents the energy required to disassemble the nucleus, peaking around iron-56 for maximum stability. Radioactive decay follows the exponential law N = N_0 e^{-\lambda t}, with decay constant \lambda and half-life t_{1/2} = \ln 2 / \lambda, derived from the probabilistic rate dN/dt = -\lambda N and verified in carbon-14 dating. Decay modes include alpha emission (helium-4 nucleus, reducing Z by 2 and mass by 4), beta-minus (neutron to proton, emitting electron and antineutrino, increasing Z by 1), beta-plus (proton to neutron, emitting positron and neutrino), and gamma (excited nucleus de-exciting via high-energy photon). Fission of heavy nuclei like uranium-235, induced by neutron absorption, splits into fragments with higher binding energy per nucleon, releasing ~200 MeV per event and sustaining chain reactions in reactors; fusion of light nuclei, such as in stellar cores, combines deuterium and tritium to form helium, yielding ~17.6 MeV and powering the sun via proton-proton chains.[41]/10%3A__Nuclear_Physics/10.04%3A_Radioactive_Decay)/10%3A__Nuclear_Physics/10.04%3A_Radioactive_Decay)Examination
Format and Content
The AP Physics 2 exam is a 3-hour assessment administered annually in May, available in a hybrid digital format where multiple-choice questions are completed via the College Board’s Bluebook app and free-response questions are handwritten in provided booklets.[3] This structure ensures accessibility while integrating technology for efficiency. Section I consists of multiple-choice questions, accounting for 50% of the total score, with approximately 40 questions to be completed in 80 minutes. Calculators are permitted throughout this section, aligning with the policy for all AP Physics exams starting in 2025. Questions are distributed proportionally across the exam's content units, reflecting the curriculum's emphasis—for instance, 15–18% on thermodynamics, 15–18% on electric force, field, and potential, and 15–18% on electric circuits, with the remaining units (magnetism and electromagnetism, geometric optics, waves, sound, and physical optics, and modern physics) each comprising 12–15%.[5] Section II, also 50% of the score, features four free-response questions over 100 minutes, with calculators allowed. These include one experimental design question (worth 12–20 points), one qualitative-quantitative translation question (7–10 points), one paragraph argument question (7 points), and one mathematical routines question (12 points). The questions draw from the curriculum units and emphasize application through scenarios involving graphs, diagrams, and laboratory contexts, avoiding isolated factual recall. The multiple-choice section is scored out of 40 points, while the free-response section is scored out of approximately 40 points based on detailed rubrics for each question; these raw scores from both sections are scaled and equally weighted (50% each) to compute the final composite score.[5] In 2025, the exam adopted a unified format across all AP Physics courses, reducing the overall length and eliminating multi-select multiple-choice questions to focus solely on single-select formats, enhancing clarity and alignment with course objectives.[3]Science Practices
The AP Physics 2 course integrates six science practices that emphasize the development of essential skills for scientific inquiry and problem-solving in physics. These practices are assessed across the multiple-choice and free-response sections of the exam and are woven throughout the curriculum to foster a deep understanding of physical concepts. Students are expected to apply these practices in analyzing systems, conducting investigations, and communicating scientific reasoning.[5] Practice 1: Modeling involves constructing and using representations, such as free-body diagrams, graphs, and circuit diagrams, to analyze physical systems and predict their behavior. This practice helps students simplify complex phenomena for deeper analysis, accounting for 10-16% of multiple-choice questions and 20-35% of free-response questions on the exam.[5] Practice 2: Mathematical Routines requires students to justify the selection of equations, perform calculations, and estimate numerical values to solve problems quantitatively. It supports the application of algebraic manipulations and functional relationships in physics contexts, representing 15-27% of multiple-choice questions and 30-40% of free-response questions.[5] Practice 3: Scientific Questioning focuses on designing experiments, selecting relevant data, and evaluating the validity of models to address scientific inquiries. Students learn to pose testable questions and refine approaches based on evidence, comprising 5-13% of multiple-choice questions and 35-45% of free-response questions.[5] Practice 4: Experimental Design entails planning detailed procedures, identifying sources of error, and interpreting experimental results to draw conclusions about physical laws. This practice is primarily integrated into free-response questions that simulate laboratory scenarios, emphasizing procedural rigor and error analysis.[5] Practice 5: Data Analysis, often intertwined with Practices 3 and 4, involves applying statistical methods, linearizing graphs, and identifying patterns in data sets to validate hypotheses or models. It equips students with tools to handle experimental uncertainties and graphical interpretations effectively.[5] Practice 6: Argumentation centers on making claims supported by evidence, justifying reasoning, and explaining physical phenomena using principles from the course. This practice promotes clear communication of scientific ideas, covering 12-20% of multiple-choice questions and 20-30% of free-response questions.[5] Laboratory work is a cornerstone of the course, requiring at least 8 hands-on investigations that dedicate 25% of instructional time to inquiry-based activities. These labs particularly emphasize Practices 3 through 6, where students design experiments, analyze data from real-world setups like measuring electric fields or wave interference, and argue conclusions based on results, bridging theoretical content with practical application.[5]Scoring and Distributions
The AP Physics 2 exam employs a criterion-referenced scoring system, converting students' raw performance into a 1-5 scale that reflects mastery of course content and science practices, without curving based on peer performance; scores of 3 or higher typically qualify for college credit at many institutions.[42] The multiple-choice section includes 40 questions, each awarded 1 point for correct answers and machine-scored, while the free-response section features 4 questions evaluated via rubrics that grant partial credit for partial understanding. A chief reader, who is a college or university faculty member, develops the scoring guidelines and oversees the annual AP Reading to ensure consistent and fair evaluation of free-response answers.[42] Final composite scores are released to students and educators in July.[43] Global score distributions for AP Physics 2 have shown steady improvement since the course redesign in 2015, with the percentage of students scoring 3 or higher rising from 55.6% that year to 72.6% in 2025, reflecting greater familiarity with the exam's emphasis on conceptual understanding and inquiry-based skills.[44] This trend includes higher proportions of top scores (4 and 5), as seen in the table below summarizing select years:| Year | % Score 5 | % Score 4 | % Score 3 | % 3+ | Mean Score | Test Takers |
|---|---|---|---|---|---|---|
| 2015 | 8.5 | 13.7 | 33.5 | 55.6 | 2.77 | 20,533 |
| 2020 | 14.0 | 24.3 | 35.0 | 73.3 | 3.20 | 21,835 |
| 2024 | 19.1 | 18.0 | 33.4 | 70.5 | 3.20 | 22,804 |
| 2025 | 21.8 | 28.8 | 22.0 | 72.6 | 3.38 | 24,211 |