AP Physics 2: Algebra-Based Vocabulary

Absolute temperature scale

Scale, such as Kelvin, with a zero point that is absolute zero.

Example: "When calculating the efficiency of a heat engine using e = 1 - TC/TH, both temperatures must be expressed in Kelvin on the         , since a temperature of 0 K represents the complete absence of thermal energy and cannot be expressed as a negative value."

Absorption spectrum

Absorption spectroscopy is spectroscopy that involves techniques that measure the absorption of electromagnetic radiation, as a function of frequency or wavelength, due to its interaction with a sample. The sample absorbs energy, i.e., photons, from the radiating field. The intensity of the absorption varies as a function of frequency, and this variation is the absorption spectrum.

Example: "When white light passes through a cool gas of hydrogen atoms, the resulting          shows dark lines at 656 nm, 486 nm, and 434 nm, corresponding to the specific photon energies that electrons absorb to jump from lower to higher energy levels."

AC circuit

Alternating current (AC) is an electric current that periodically reverses direction and changes its magnitude continuously with time, in contrast to direct current (DC), which flows only in one direction. Alternating current is the form in which electric power is delivered to businesses and residences, and it is the form of electrical energy that consumers typically use when they plug kitchen appliances, televisions, fans and electric lamps into a wall socket. The abbreviations AC and DC are of.

Example: "In an          powered by a 120 V (rms) source at 60 Hz, an inductor and capacitor connected in series will exhibit a resonant frequency at which their reactances cancel, allowing maximum current to flow through the resistive load."

Ac current

Current that fluctuates sinusoidally with time at a fixed frequency.

Example: "The          in a household circuit follows the relation i(t) = Imax sin(2πft), where Imax is the peak current and f = 60 Hz, meaning the current reverses direction 120 times per second."

Ac voltage

Voltage that fluctuates sinusoidally with time at a fixed frequency.

Example: "A transformer steps up the          from 120 V to 12,000 V for long-distance transmission because power losses (P = I²R) are minimized when the current is reduced by increasing the voltage."

Action-at-a-distance

Electric force is an action-at-a-distance force. In Lesson 4 of this unit, we will explore this concept of action-at-a-distance using a different concept known as the electric field .

Example: "The fact that a proton exerts a repulsive Coulomb force of F = kq₁q₂/r² on another proton across empty space, without any physical contact between them, is a classic example of          mediated by the electric field."

Adiabatic process

An adiabatic process (adiabatic from Ancient Greek ἀδιάβατος (adiábatos) 'impassable') is a type of thermodynamic process whereby a transfer of energy between the thermodynamic system and its environment is neither accompanied by a transfer of entropy nor of amounts of constituents. Unlike an isothermal process, an adiabatic process transfers energy to the surroundings only as work and/or mass flow. As a key concept in thermodynamics, the adiabatic process supports the theory that explains the.

Example: "When a gas in a well-insulated cylinder is compressed rapidly so that Q = 0, the          causes the internal energy to increase entirely from work done on the gas, raising its temperature according to ΔU = W."

Alpha (α) rays

One of the types of rays emitted from the nucleus of an atom as alpha particles.

Example: "Alpha rays emitted from a radium nucleus are deflected by a magnetic field, confirming they carry a positive charge of +2e and a mass of approximately 4 u, consistent with a helium-4 nucleus."

Alpha decay

Alpha decay or α-decay is a type of radioactive decay in which an atomic nucleus emits an alpha particle (helium nucleus). The parent nucleus transforms or "decays" into a daughter product, with a mass number that is reduced by four and an atomic number that is reduced by two. An alpha particle is identical to the nucleus of a helium-4 atom, which consists of two protons and two neutrons.

Example: "When uranium-238 undergoes         , the nucleus emits a helium-4 nucleus, producing thorium-234 and reducing the atomic number by 2 and the mass number by 4, as represented by ²³⁸U → ²³⁴Th + ⁴He."

Alternating current

It’s probably no surprise that we call this alternating current . The wall outlets in your home supply alternating current to the electrical cord that you plug into them. Like it or not, alternating current is what gets generated when we have a loop of wire spinning in a magnetic field. Whenever we generate electricity, we produce alternating current. That’s where alternating current comes from in the first place!

Example: "A generator produces          as a rectangular coil rotates at angular frequency ω in a uniform magnetic field B, inducing an EMF given by ε = NBAω sin(ωt) that continuously reverses polarity."

Ampere's law

In classical electromagnetism, Ampère's circuital law, often simply called Ampère's law, and sometimes Oersted's law, relates the circulation of a magnetic field around a closed loop to the electric current passing through that loop. The law was inspired by Hans Christian Ørsted's 1820 discovery that an electric current generates a magnetic field. This finding prompted theoretical and experimental work by André-Marie Ampère and others, eventually leading to the formulation of the law in its mode.

Example: "Applying         , ∮ B·dl = μ₀I_enc, to a circular Amperian loop of radius r around a long straight wire carrying current I gives B(2πr) = μ₀I, yielding a magnetic field B = μ₀I/(2πr) that decreases with distance."

Ampère’s law

Physical law that states that the line integral of the magnetic field around an electric current is proportional to the current.

Example: "To find the magnetic field inside a solenoid with n turns per unit length,          applied to a rectangular Amperian loop gives B = μ₀nI, showing the field is uniform inside and zero outside."

Angle of deviation

The amount of overall refraction caused by the passage of a light ray through a prism is often expressed in terms of the angle of deviation ( ). The angle of deviation is the angle made between the incident ray of light entering the first face of the prism and the refracted ray that emerges from the second face of the prism. Because of the different indices of refraction for the different wavelengths of visible light, the angle of deviation varies with wavelength.

Example: "When white light passes through a glass prism, violet light experiences a greater          than red light because violet has a shorter wavelength and a higher index of refraction in the glass, demonstrating dispersion."

Angle of incidence

The angle between the incident ray and the normal is known as the angle of incidence . (These two angles are labeled with the Greek letter "theta" accompanied by a subscript; read as "theta-i" for angle of incidence and "theta-r" for angle of reflection.) The law of reflection states that when a ray of light reflects off a surface, the angle of incidence is equal to the angle of reflection.

Example: "A laser beam strikes a mirror at an          of 30° measured from the normal; by the law of reflection, the angle of reflection is also 30°, so the beam bounces away at 30° on the opposite side of the normal."

Angle of reflection

The angle between the reflected ray and the normal is known as the angle of reflection . (These two angles are labeled with the Greek letter "theta" accompanied by a subscript; read as "theta-i" for angle of incidence and "theta-r" for angle of reflection.) The law of reflection states that when a ray of light reflects off a surface, the angle of incidence is equal to the angle of reflection.

Example: "A ray of light hitting a flat mirror with an angle of incidence of 45° will leave with an          of 45°, meaning the reflected ray is symmetric to the incident ray about the normal to the mirror's surface."

Angle of refraction

Similarly, the angle that the refracted ray makes with the normal line is referred to as the angle of refraction . The angle of incidence and angle of refraction are denoted by the following symbols:.

Example: "Using Snell's law, n₁ sin θ₁ = n₂ sin θ₂, when a light ray travels from air (n = 1.00) into glass (n = 1.50) at an angle of incidence of 30°, the          is approximately 19.5°, bending the ray toward the normal."

Antinodal lines

The antinodes (points where the waves always interfere constructively) seem to be located along lines - creatively called antinodal lines . The two-point source interference pattern is characterized by a pattern of alternating nodal and antinodal lines. The nodal and antinodal lines are included on the diagram below.

Example: "In Young's double-slit experiment with two coherent sources separated by distance d,          occur where the path difference equals an integer multiple of the wavelength (Δr = mλ), producing bright fringes on the screen."

Archimedes principle

Archimedes' principle states that the upward buoyant force that is exerted on a body immersed in a fluid, whether fully or partially, is equal to the weight of the fluid that the body displaces. Archimedes' principle is a law of physics fundamental to fluid mechanics. It was formulated by Archimedes of Syracuse.

Example: "A steel ball with a volume of 50 cm³ submerged in water experiences an upward buoyant force equal to the weight of water displaced: Fb = ρwater × V × g = (1000 kg/m³)(50 × 10⁻⁶ m³)(9.8 m/s²) ≈ 0.49 N, as described by Archimedes' principle."

Atomic nucleus

The atomic nucleus is the small, dense region consisting of protons and neutrons at the center of an atom, discovered in 1911 by Ernest Rutherford at the University of Manchester based on the 1909 Geiger–Marsden gold foil experiment. After the discovery of the neutron in 1932, models for a nucleus composed of protons and neutrons were quickly developed by Dmitri Ivanenko and Werner Heisenberg. An atom is composed of a positively charged nucleus, with a cloud of negatively charged electrons surr.

Example: "Rutherford's gold foil experiment demonstrated that the          is a tiny, dense, positively charged core because most alpha particles passed straight through the gold atoms, while a small fraction scattered at large angles."

Atomic number

The atomic number or nuclear charge number (symbol Z) of a chemical element is the charge number of its atomic nucleus. For ordinary nuclei composed of protons and neutrons, this is equal to the proton number (np) or the number of protons found in the nucleus of every atom of that element. The atomic number can be used to uniquely identify ordinary chemical elements.

Example: "Carbon has an          Z = 6, meaning every neutral carbon atom contains exactly 6 protons in its nucleus, which determines its chemical identity and its position in the periodic table."

Away from the normal

From this analogy and the diagram above, we see that the refracted ray (in red) is further away from the normal then the incident ray (in blue). In such an instance as this, we would say that the path of the students has bent away from the normal .

Example: "When light travels from glass (n = 1.5) into air (n = 1.0), it bends         , increasing its angle of refraction relative to the angle of incidence, as required by Snell's law n₁ sin θ₁ = n₂ sin θ₂."

Back emf

Emf generated by a running motor, because it consists of a coil turning in a magnetic field; it opposes the voltage powering the motor.

Example: "As an electric motor speeds up, the          it generates grows and opposes the supply voltage, reducing the net voltage driving current through the armature coil and limiting the motor's current draw at operating speed."

Background radiation

Background radiation is a measure of the level of ionizing radiation present in the environment at a particular location which is not due to deliberate introduction of radiation sources. Background radiation originates from a variety of sources, both natural and artificial. These include both cosmic radiation and environmental radioactivity from naturally occurring radioactive materials (such as radon and radium), as well as man-made medical X-rays, fallout from nuclear weapons testing and nucle.

Example: "Before measuring the activity of a weak radioactive sample, a physicist subtracts the          count rate—caused by cosmic rays and naturally occurring radon gas—to obtain the sample's true activity in becquerels."

Balmer series

Spectral lines corresponding to electron transitions to/from the n=2n=2 state of the hydrogen atom, described by the Balmer formula.

Example: "The visible red line at 656 nm in hydrogen's emission spectrum belongs to the          and corresponds to an electron transitioning from the n = 3 level down to the n = 2 level, releasing a photon of energy E = hc/λ ≈ 1.89 eV."

Baryon number

Baryon number has the value B=+1B=+1 for baryons, –1–1 for antibaryons, and 0 for all other particles and is conserved in particle interactions.

Example: "In the reaction p + p → p + p + p + p̄,          is conserved because the initial          is B = +2 and the final          is also +2 (three protons at B = +1 and one antiproton at B = −1)."

Base current

Current drawn from the base n-type material in a transistor.

Example: "In an NPN transistor biased in the active region, a small          of 10 μA controls a much larger collector current of 1 mA, demonstrating a current gain (β) of 100 that makes the transistor useful as an amplifier."

Bernoulli's principle

Bernoulli's principle is a key concept in fluid dynamics that relates pressure, speed and height. For example, for a fluid flowing horizontally, Bernoulli's principle states that an increase in the speed occurs simultaneously with a decrease in pressure. The principle is named after the Swiss mathematician and physicist Daniel Bernoulli, who published it in his book Hydrodynamica in 1738.

Example: "According to         , P₁ + ½ρv₁² + ρgh₁ = P₂ + ½ρv₂² + ρgh₂, when water flowing through a horizontal pipe speeds up in a constricted section, its pressure drops proportionally, which can be measured with a manometer."

Beta (ββ) rays

One of the types of rays emitted from the nucleus of an atom as beta particles.

Example: "Beta rays emitted from a cobalt-60 source are deflected toward the positive plate in an electric field, confirming they carry negative charge and consist of high-energy electrons (β⁻ particles) ejected from the nucleus."

Beta decay

In nuclear physics, beta decay (β-decay) is a type of radioactive decay in which an atomic nucleus emits a beta particle (fast energetic electron or positron), transforming into an isobar of that nuclide. For example, beta decay of a neutron transforms it into a proton by the emission of an electron accompanied by an antineutrino; or, conversely a proton is converted into a neutron by the emission of a positron with a neutrino in what is called positron emission. Neither the beta particle nor it.

Example: "In         , carbon-14 decays to nitrogen-14 as a neutron converts to a proton: ¹⁴C → ¹⁴N + e⁻ + ν̄_e, conserving both charge and lepton number while the atomic number increases by one."

Binding energy

Nuclear binding energy in experimental physics is the minimum energy that is required to disassemble the nucleus of an atom into its constituent protons and neutrons, known collectively as nucleons. The binding energy for stable nuclei is always a positive number, as the nucleus must gain energy for the nucleons to move apart from each other. Nucleons are attracted to each other by the strong nuclear force.

Example: "The          per nucleon for iron-56 is approximately 8.8 MeV/nucleon—the highest of any isotope—which explains why nuclear fusion reactions below iron release energy while fission reactions above iron also release energy."

Biot-Savart law

An equation giving the magnetic field at a point produced by a current-carrying wire.

Example: "Using the         , dB = (μ₀/4π)(I dl × r̂)/r², one can calculate the magnetic field at the center of a circular current loop of radius R as B = μ₀I/(2R), directed perpendicular to the plane of the loop."

Blackbody radiation

Black-body radiation is the thermal electromagnetic radiation within, or surrounding, a body in thermodynamic equilibrium with its environment, emitted by a black body (an idealized opaque, non-reflective body). It has a specific continuous spectrum that depends only on the body's temperature. A perfectly-insulated enclosure which is in thermal equilibrium internally contains black-body radiation and will emit it through a hole made in its wall, provided the hole is small enough to have a neglig.

Example: "A star with a surface temperature of 6000 K emits          with a peak wavelength of λ_max = b/T = (2.9 × 10⁻³ m·K)/(6000 K) ≈ 480 nm, placing it in the visible blue-green range of the spectrum."

Bohr magneton

Magnetic moment of an electron, equal to 9.3×10−24J/T9.3×10−24J/T or 5.8×10−5eV/T5.8×10−5eV/T.

Example: "The intrinsic magnetic moment of an electron is approximately one          (μ_B = 9.3 × 10⁻²⁴ J/T), which determines how strongly the electron interacts with an external magnetic field, as seen in the Zeeman effect."

Bohr model

In atomic physics, the Bohr model or Rutherford–Bohr model is an obsolete model of the atom that incorporated some early quantum concepts. Developed from 1911 to 1918 by Niels Bohr and building on Ernest Rutherford's discovery of the atom's nucleus, it supplanted the plum pudding model of J. J.

Example: "The          predicts that an electron in the n = 3 orbit of hydrogen has a radius of r = n²a₀ = 9 × 0.053 nm = 0.476 nm and an energy of E = −13.6 eV/n² = −1.51 eV."

Boltzmann constant

The Boltzmann constant (kB or k) is the proportionality factor that relates the average relative thermal energy of particles in a gas with the thermodynamic temperature of the gas. It occurs in the definitions of the kelvin (K) and the molar gas constant, in Planck's law of black-body radiation and Boltzmann's entropy formula, and is used in calculating thermal noise in resistors. The Boltzmann constant has dimensions of energy divided by temperature, the same as entropy and heat capacity.

Example: "The average kinetic energy of a monatomic ideal gas molecule at temperature T is KEavg = (3/2)kBT, so at room temperature (T = 300 K) the average kinetic energy is approximately (3/2)(1.38 × 10⁻²³ J/K)(300 K) ≈ 6.2 × 10⁻²¹ J."

Born interpretation

States that the square of a wave function is the probability density.

Example: "According to the         , if the wave function of an electron is ψ(x), then |ψ(x)|² gives the probability density of finding the electron at position x, so the probability of detection in a region dx is |ψ(x)|² dx."

Boundary behavior

The behavior of a wave (or pulse) upon reaching the end of a medium is referred to as boundary behavior . When one medium ends, another medium begins; the interface of the two media is referred to as the boundary and the behavior of a wave at that boundary is described as its boundary behavior. The questions that are listed above are the types of questions we seek to answer when we investigate the boundary behavior of waves.

Example: "When a wave pulse on a string reaches the boundary where the string is tied to a heavier rope, part of the pulse is transmitted into the heavier rope and part is reflected back inverted—this          depends on the change in medium impedance."

Braking radiation

Radiation produced by targeting metal with a high-energy electron beam (or radiation produced by the acceleration of any charged particle in a material).

Example: "When high-energy electrons in an X-ray tube are rapidly decelerated by the tungsten target, they emit          (Bremsstrahlung) across a continuous spectrum, with maximum photon energy equal to the full kinetic energy of the incident electrons: E_max = eV."

Breakdown voltage

In a diode, the reverse bias voltage needed to cause an avalanche of current.

Example: "A Zener diode has a specified          of 5.1 V; when the reverse bias across it reaches this value, an avalanche of current flows through it, allowing it to function as a voltage regulator in a DC circuit."

Brewster's angle

Brewster's angle (also known as the polarization angle) is the angle of incidence at which light with a particular polarization is perfectly transmitted through a transparent dielectric surface, with no reflection. When unpolarized light is incident at this angle, the light that is reflected from the surface is perfectly polarized. The angle is named after the Scottish physicist Sir David Brewster (1781–1868).

Example: "When light in air strikes a glass surface (n = 1.52) at          θ_B = arctan(n₂/n₁) = arctan(1.52) ≈ 56.7°, the reflected light is completely polarized parallel to the surface, a property exploited in polarizing filters."

Brewster’s law

Tanθb=n2n1tanθb=n2n1, where n1n1 is the medium in which the incident and reflected light travel and n2n2 is the index of refraction of the medium that forms the interface that reflects the light.

Example: "         states that tan θB = n₂/n₁; for light passing from water (n₁ = 1.33) into a glass lens (n₂ = 1.50), Brewster's angle is θB = arctan(1.50/1.33) ≈ 48.4°, at which angle reflected light is fully polarized."

Carnot cycle

A Carnot cycle is an ideal thermodynamic cycle proposed by French physicist Sadi Carnot in 1824 and expanded upon by others in the 1830s and 1840s. By Carnot's theorem, it provides an upper limit on the efficiency of any classical thermodynamic engine during the conversion of heat into work, or conversely, the efficiency of a refrigeration system in creating a temperature difference through the application of work to the system. In a Carnot cycle, a system or engine transfers energy in the form.

Example: "A          operating between a hot reservoir at TH = 600 K and a cold reservoir at TC = 300 K achieves a maximum theoretical efficiency of e = 1 - TC/TH = 1 - 300/600 = 50%, which no real engine can exceed."

Carnot engine

Carnot heat engine, refrigerator, or heat pump that operates on a Carnot cycle.

Example: "A          absorbs 1000 J of heat from a reservoir at 500 K and rejects 600 J to a reservoir at 300 K, performing 400 J of work with an efficiency of 40%, matching the theoretical limit e = 1 - TC/TH = 40%."

Carnot principle

Principle governing the efficiency or performance of a heat device operating on a Carnot cycle: any reversible heat device working between two reservoirs must have the same efficiency or performance coefficient, greater than that of an irreversible heat device operating between the same two reservoirs.

Example: "The          establishes that any irreversible heat engine operating between reservoirs at 800 K and 400 K must have an efficiency less than the Carnot limit of 50%, regardless of the working substance or engine design."

Cassegrain design

Arrangement of an objective and eyepiece such that the light-gathering concave mirror has a hole in the middle, and light then is incident on an eyepiece lens.

Example: "The Hubble Space Telescope uses a          in which a large primary concave mirror collects light and reflects it onto a smaller convex secondary mirror, which then directs the converging beam back through a hole in the primary to the detector."

Celsius scale

Temperature scale in which the freezing point of water is 0°C0°C and the boiling point of water is 100°C100°C.

Example: "To convert a temperature of 25°C to the absolute Kelvin scale for use in the ideal gas law PV = nRT, one adds 273.15 to obtain T = 298.15 K, since the          is offset from the Kelvin scale by 273.15 degrees."

Center of curvature

The point in the center of the sphere from which the mirror was sliced is known as the center of curvature and is denoted by the letter C in the diagram below. Midway between the vertex and the center of curvature is a point known as the focal point ; the focal point is denoted by the letter F in the diagram below. The distance from the vertex to the center of curvature is known as the radius of curvature (represented by R ). Since the focal point is the midpoint of the line segment adjoining th.

Example: "A concave mirror has a radius of curvature R = 20 cm, so its          C is 20 cm from the vertex and its focal point F lies halfway between them at f = R/2 = 10 cm from the mirror's surface."

Central antinodal line

This antinodal line is referred to as the central antinodal line . More antinodal lines are present to the left and to the right of the central antinodal line. The nodal lines are also named; the first nodal line to the left or to the right of the central antinodal line is referred to as the first nodal line .

Example: "In a two-source interference pattern, the          lies along the perpendicular bisector of the two sources, where the path difference is zero (Δr = 0) and waves always arrive in phase to produce maximum constructive interference."

Charge conservation

In physics, charge conservation is the principle, of experimental nature, that the total electric charge in an isolated system never changes. The net quantity of electric charge, the amount of positive charge minus the amount of negative charge in the universe, is always conserved. Charge conservation, considered as a physical conservation law, implies that the change in the amount of electric charge in any volume of space is exactly equal to the amount of charge flowing into the volume minus th.

Example: "When a beta particle (electron, charge −e) is emitted during beta decay, the daughter nucleus gains a charge of +e to compensate, ensuring total charge is conserved in the isolated system just as required by         ."

Charging by conduction

In this section of Lesson 2, a third method of charging - charging by conduction - will be discussed.

Example: "When a negatively charged rod is touched directly to an uncharged metal sphere, electrons flow from the rod into the sphere by         , leaving the sphere with a net negative charge after the rod is removed."

Charging by induction

In this section of Lesson 2, the charging by induction method will be discussed. An understanding of charging by induction requires an understanding of the nature of a conductor and an understanding of the polarization process.

Example: "By bringing a positively charged rod near (but not touching) a neutral metal sphere and then grounding the sphere momentarily,          leaves the sphere with a net negative charge after the ground connection is broken and the rod removed."

Chemical group

Group of elements in the same column of the periodic table that possess similar chemical properties.

Example: "Lithium, sodium, and potassium all belong to the same          (Group 1, the alkali metals) in the periodic table, each having one valence electron that is easily ionized, giving them similar electrochemical properties."

Ciliary muscles

The lens is attached to the ciliary muscles . By carefully adjusting the lenses shape, the ciliary muscles assist the eye in the critical task of producing an image on the back of the eyeball.

Example: "When a person focuses on a nearby object, the          contract, allowing the crystalline lens to become more convex and increase its converging power, thereby decreasing the focal length to form a sharp image on the retina."

Classical (Galilean) velocity addition

Method of adding velocities when v<<c;v<<c; velocities add like regular numbers in one-dimensional motion: u=v+u′,u=v+u′, where v is the velocity between two observers, u is the velocity of an object relative to one observer, and u′u′ is the velocity relative to the other observer.

Example: "A ball thrown at 10 m/s forward inside a train moving at 30 m/s is observed from the ground to travel at u = v + u' = 30 + 10 = 40 m/s using         , valid because both speeds are far less than c."

Coefficient of linear expansion

(αα) material property that gives the change in length, per unit length, per 1-°C1-°C change in temperature; a constant used in the calculation of linear expansion; the coefficient of linear expansion depends to some degree on the temperature of the material.

Example: "A steel rod (α = 1.2 × 10⁻⁵ °C⁻¹) of length 2.0 m will elongate by ΔL = αL₀ΔT = (1.2 × 10⁻⁵)(2.0)(100) = 2.4 × 10⁻³ m = 2.4 mm when heated from 20°C to 120°C, which structural engineers must account for in bridge design."

Coherent light

(This is often referred to as coherent light .) To accomplish this, Thomas Young used a single light source and projected the light onto two pinholes.

Example: "A laser produces          in which all photons share the same wavelength and phase, which is essential for observing a stable, high-contrast interference pattern in experiments such as Young's double-slit setup."

Color addition

The production of various colors of light by the mixing of the three primary colors of light is known as color addition . The color addition principles discussed on this page can be used to make predictions of the colors that would result when different colored lights are mixed. In the next part of Lesson 2 , we will learn how to use the principles of color addition to determine why different objects look specific colors when illuminated with various colors of light.

Example: "         of red and green light in equal intensities produces yellow light because the combined wavelengths stimulate both the red-sensitive and green-sensitive cones in the human eye without stimulating the blue-sensitive cones."

Color Observed

See Answer Paint One Paint Two Color Observed Cyan Magenta Blue Magenta Yellow Red Cyan Yellow Green Cyan, Magenta & Yellow Black a.

Example: "When cyan paint (which absorbs red) and yellow paint (which absorbs blue) are mixed, the          is green, because only green light is reflected by both pigments while red and blue are absorbed—an application of subtractive color mixing."

Combination circuit

A third type of circuit involves the dual use of series and parallel connections in a circuit; such circuits are referred to as compound circuits or combination circuits. This is an example of a combination circuit .

Example: "In a          containing two 4 Ω resistors in parallel (giving 2 Ω equivalent) connected in series with a 3 Ω resistor, the total resistance is 5 Ω; with a 10 V source, the total current is I = V/R = 2 A."

Compass rose

Nomadic people from the Middle East were the first to use the compass rose to mark the direction of the rising and setting of stars in the sky.

Example: "Early navigators used the          to determine their heading relative to magnetic north, a direction determined by Earth's internal magnetic field, which causes compass needles to align with the field lines running from geographic south to geographic north."

Complementary colors

Any two colors of light that when mixed together in equal intensities produce white are said to be complementary colors of each other. Thus, red light and cyan light (which is equivalent to blue + green light) represent a pair of complementary colors of light; they add together to produce white light.

Example: "Vincent van Gogh exploited the optical vibration created by         —particularly the opposition of intense yellow and violet in The Starry Night—to generate emotional intensity and visual energy that transcended straightforward naturalistic depiction."

Compound microscope

Microscope constructed from two convex lenses, the first serving as the eyepiece and the second serving as the objective lens.

Example: "A          uses an objective lens of short focal length (e.g., f = 4 mm) to produce a highly magnified real image that is then further magnified by the eyepiece lens, resulting in a total magnification that is the product of both magnifications."

Compton effect

The change in wavelength when an X-ray is scattered by its interaction with some materials.

Example: "The          demonstrates the particle nature of light: when an X-ray photon of wavelength 0.071 nm scatters off a loosely bound electron, the scattered photon has a longer wavelength because it transferred some of its momentum (p = h/λ) to the electron."

Compton scattering

Compton scattering (or the Compton effect) is the quantum theory of scattering of a high-frequency photon through an interaction with a charged particle, usually an electron. Specifically, when the photon interacts with a loosely bound electron, it releases the electron from an outer valence shell of an atom or molecule. The effect was discovered in 1923 by Arthur Holly Compton while researching the scattering of X-rays by light elements, which earned him the Nobel Prize in Physics in 1927.

Example: "         confirmed that photons carry momentum p = h/λ; when a photon collides with an electron at rest, conservation of energy and momentum requires the scattered photon to have a longer wavelength than the incident photon."

Compton shift

Difference between the wavelengths of the incident X-ray and the scattered X-ray.

Example: "The          formula Δλ = (h/me c)(1 − cos θ) predicts that an X-ray scattered at θ = 90° will have its wavelength increased by the Compton wavelength h/(me c) = 2.43 × 10⁻¹² m."

Concave mirror

A curved mirror is a mirror with a curved reflecting surface. The surface may be either convex (bulging outward) or concave (recessed inward). Most curved mirrors have surfaces that are shaped like part of a sphere, but other shapes are sometimes used in optical devices.

Example: "A          with a focal length of 15 cm will produce a real, inverted, magnified image when an object is placed 20 cm from the mirror, as calculated using the mirror equation 1/f = 1/do + 1/di."

Concave mirrors

Were silvered on the inside of the sphere and convex mirrors were silvered on the outside of the sphere. In Lesson 3 we will focus on concave mirrors and in Lesson 4 we will focus on convex mirrors.

Example: "         converge parallel rays of light to a focal point in front of the mirror surface, making them useful in reflecting telescopes that collect and focus light from distant stars onto a detector at the focal plane."

Conduction (heat)

Thermal conduction is the diffusion of thermal energy (heat) within one material or between materials in contact. The higher temperature object has molecules with more kinetic energy; collisions between molecules distributes this kinetic energy until an object has the same kinetic energy throughout. Thermal conductivity, represented by k, is a property that relates the rate of heat loss per unit area to its rate of change of temperature.

Example: "Heat conduction through a copper rod of cross-sectional area A, length L, and thermal conductivity k = 385 W/(m·K) is given by Q/t = kAΔT/L; a large k value explains why copper rapidly conducts heat away from a hot object."

Conduction band

Above the valence band, the next available band in the energy structure of a crystal.

Example: "In a semiconductor like silicon, electrons thermally excited across the band gap into the          are free to move through the crystal lattice and carry electric current, unlike electrons confined to the valence band."

Conductor (material)

In physics and electrical engineering, a conductor is an object or type of material that allows the flow of charge (electric current) in one or more directions. Materials made of metal are common electrical conductors. The flow of negatively charged electrons generates electric current, positively charged holes, and positive or negative ions in some cases.

Example: "In a metallic conductor like copper, the outermost electrons are delocalized and free to drift in response to an electric field, giving copper a very low resistivity (ρ ≈ 1.7 × 10⁻⁸ Ω·m) and excellent current-carrying ability."

Conservation of energy.

It turns out that Lenz’s Law is a result of the magnetic force and the conservation of energy.

Example: "Lenz's law is a consequence of conservation of energy: if the induced current in a loop created an EMF that aided the change in flux rather than opposing it, the current would grow without bound, creating energy from nothing in violation of         "

Constructive interference

In physics, interference is a phenomenon in which two coherent waves are combined by adding their intensities or displacements with due consideration for their phase difference. The resultant wave may have greater amplitude (constructive interference) or lower amplitude (destructive interference) if the two waves are in phase or out of phase, respectively. Interference effects can be observed with all types of waves, for example, light, radio, acoustic, surface water waves, gravity waves, or mat.

Example: "When two water waves of amplitude A = 0.5 m arrive at a point in phase (path difference = nλ), they undergo         , producing a resultant wave of amplitude 2A = 1.0 m at that location."

Continuity equation

A continuity equation or transport equation is an equation that describes the transport of some quantity. It is particularly simple and powerful when applied to a conserved quantity, but it can be generalized to apply to any extensive quantity. Since mass, energy, momentum, electric charge and other natural quantities are conserved under their respective appropriate conditions, a variety of physical phenomena may be described using continuity equations.

Example: "The          for an incompressible fluid, A₁v₁ = A₂v₂, predicts that when water flows from a pipe of cross-sectional area 0.02 m² at 2 m/s into a section with area 0.01 m², the speed doubles to 4 m/s."

Continuous charge distribution

Total source charge composed of so large a number of elementary charges that it must be treated as continuous, rather than discrete.

Example: "To find the electric field on the axis of a uniformly charged ring, the ring is treated as a          and integrated using dE = k dq / r², because the ring contains so many closely spaced charges that a discrete sum is impractical."

Conventional current

Current that flows through a circuit from the positive terminal of a battery through the circuit to the negative terminal of the battery.

Example: "In a circuit,          flows from the positive terminal of the battery through the external resistors to the negative terminal, even though the actual charge carriers (electrons) move in the opposite direction inside the wire."

Converging lens

A lens is a transmissive optical device that focuses or disperses a light beam by means of refraction. A simple lens consists of a single piece of transparent material, while a compound lens consists of several simple lenses (elements), usually arranged along a common axis. Lenses are made from materials such as glass or plastic and are ground, polished, or molded to the required shape.

Example: "A          with a focal length of 10 cm will form a real, inverted image of an object placed 30 cm away at an image distance calculated from 1/f = 1/do + 1/di: di = 15 cm, with a magnification of m = −di/d_o = −0.5."

Convex mirror

A curved mirror is a mirror with a curved reflecting surface. The surface may be either convex (bulging outward) or concave (recessed inward). Most curved mirrors have surfaces that are shaped like part of a sphere, but other shapes are sometimes used in optical devices.

Example: "A          always produces a virtual, upright, and diminished image regardless of object distance, which is why they are used as security mirrors in stores—they provide a wide field of view covering a large area."

Convex mirrors

Concave mirrors were silvered on the inside of the sphere and convex mirrors were silvered on the outside of the sphere. In Lesson 3 we will focus on concave mirrors and in Lesson 4 we will focus on convex mirrors.

Example: "         have a negative focal length and diverge reflected rays, so the mirror equation 1/f = 1/do + 1/di always yields a positive image distance smaller than the object distance, corresponding to a virtual, reduced image."

Copenhagen interpretation

States that when an observer is not looking or when a measurement is not being made, the particle has many values of measurable quantities, such as position.

Example: "According to the         , before a measurement collapses the wave function, an electron in a double-slit experiment does not have a definite position but rather exists as a superposition of all possible positions described by ψ(x)."

Corner reflector

Object consisting of two (or three) mutually perpendicular reflecting surfaces, so that the light that enters is reflected back exactly parallel to the direction from which it came.

Example: "Retroreflectors on the Moon, consisting of          made of three mutually perpendicular mirrors, reflect laser pulses sent from Earth directly back to the source regardless of the angle of incidence, enabling precise measurement of the Earth-Moon distance."

Correspondence principle

In the limit of large energies, the predictions of quantum mechanics agree with the predictions of classical mechanics.

Example: "At large quantum numbers, the          ensures that predictions from the Bohr model for hydrogen transitions between n = 100 and n = 101 match the frequency predicted by classical orbital mechanics for an electron at that radius."

Coulomb's law

Coulomb's inverse-square law, or simply Coulomb's law, is an experimental law of physics that calculates the amount of force between two electrically charged particles at rest. This electric force is conventionally called the electrostatic force or Coulomb force. Although the law was known earlier, it was first published in 1785 by French physicist Charles-Augustin de Coulomb.

Example: "        , F = kq₁q₂/r², shows that if the separation between two charges is doubled, the electrostatic force decreases by a factor of four, illustrating the inverse-square dependence on distance."

Coulomb’s law

Mathematical equation calculating the electrostatic force vector between two charged particles.

Example: "        , F = kq₁q₂/r², shows that if the separation between two charges is doubled, the electrostatic force decreases by a factor of four, illustrating the inverse-square dependence on distance."

Counterclockwise direction

Using the Field-finding Right Hand Rule , we can see that the induced current will be in the counterclockwise direction around the loop since, when our right thumb points in that direction our fingers will curl around the wire and be pointing out of the page in the area inside the loop.

Example: "When a bar magnet is pushed north-pole first toward a horizontal conducting loop, Lenz's law requires the induced current to flow in the          (viewed from above) to create a magnetic field that opposes the increasing upward flux."

Created by

The movement of a compass needle suggested a magnetic field was created by this electric current.

Example: "Oersted discovered in 1820 that a magnetic field is          electric current flowing through a wire, as demonstrated by the deflection of a compass needle placed near a current-carrying conductor."

Critical angle

In physics, total internal reflection (TIR) is the phenomenon in which waves arriving at the interface (boundary) from one medium to another (e.g., from water to air) are not refracted into the second ("external") medium, but completely reflected back into the first ("internal") medium. It occurs when the second medium has a higher wave speed (i.e., lower refractive index) than the first, and the waves are incident at a sufficiently oblique angle on the interface. For example, the water-to-air s.

Example: "For light traveling from glass (n = 1.5) to air (n = 1.0), the          is θ_c = arcsin(n₂/n₁) = arcsin(1/1.5) ≈ 41.8°; any ray striking the glass-air interface at an angle greater than this undergoes total internal reflection."

Critical mass

Minimum mass required of a given nuclide in order for self-sustained fission to occur.

Example: "Uranium-235 has a          of approximately 52 kg in an uncompressed sphere; below this mass, too many neutrons escape the surface before inducing further fissions to sustain a chain reaction."

Critical point

For a given substance, the combination of temperature and pressure above which the liquid and gas phases are indistinguishable.

Example: "For water, the          occurs at T = 374°C and P = 22.1 MPa; above this temperature and pressure, the liquid and gas phases of water are indistinguishable, forming a single supercritical fluid phase."

Crystalline lens

Light that passes through the pupil opening, will enter the crystalline lens . The crystalline lens is made of layers of a fibrous material that has an index of refraction of roughly 1.40.

Example: "The          in the human eye, with an index of refraction of about 1.40, changes curvature through the action of the ciliary muscles to adjust its focal length and keep images focused on the retina as objects move closer or farther away."

Current density

Flow of charge through a cross-sectional area divided by the area.

Example: "A copper wire of cross-sectional area 2.0 × 10⁻⁶ m² carrying a current of 4.0 A has a          of J = I/A = 4.0/2.0 × 10⁻⁶ = 2.0 × 10⁶ A/m², which is related to the electric field by J = σE."

Current-carrying wire feels a force

We might ask ourselves, “Are there any applications of using the result that a current-carrying wire feels a force in a magnetic field?” Truth is, there are hundreds of applications to this physics principle!

Example: "A current-carrying wire of length L = 0.5 m carrying current I = 3 A placed in a uniform magnetic field B = 0.4 T perpendicular to the wire feels a force F = BIL = (0.4)(3)(0.5) = 0.6 N, the principle behind electric motors."

Curved mirror

Mirror formed by a curved surface, such as spherical, elliptical, or parabolic.

Example: "A parabolic          focuses all incoming parallel rays precisely at a single focal point without spherical aberration, making it the preferred shape for telescope primary mirrors and satellite dish antennas."

Cut-off frequency

Frequency of incident light below which the photoelectric effect does not occur.

Example: "In the photoelectric effect, light incident on a sodium surface (work function φ = 2.28 eV) must exceed the          f₀ = φ/h = (2.28 × 1.6 × 10⁻¹⁹ J)/(6.626 × 10⁻³⁴ J·s) ≈ 5.5 × 10¹⁴ Hz; below this frequency, no electrons are emitted regardless of intensity."

Cut-off wavelength

Wavelength of incident light that corresponds to cut-off frequency.

Example: "The          for the photoelectric effect on zinc (work function 4.3 eV) is λ₀ = hc/φ = (6.626 × 10⁻³⁴ × 3 × 10⁸)/(4.3 × 1.6 × 10⁻¹⁹) ≈ 289 nm, which lies in the ultraviolet range."

Davisson–Germer experiment

Historically first electron-diffraction experiment that revealed electron waves.

Example: "The Davisson–Germer experiment confirmed de Broglie's hypothesis by demonstrating that electrons accelerated through 54 V produce a diffraction pattern from a nickel crystal consistent with a wavelength of λ = h/p ≈ 0.167 nm."

De Broglie wave

Matter wave associated with any object that has mass and momentum.

Example: "A proton moving at 2.0 × 10⁶ m/s has an associated          with wavelength λ = h/mv = (6.626 × 10⁻³⁴)/((1.67 × 10⁻²⁷)(2.0 × 10⁶)) ≈ 1.98 × 10⁻¹³ m, small enough to diffract from atomic-scale structures."

De Broglie wavelength

Matter waves are a central part of the theory of quantum mechanics, being half of wave–particle duality. At all scales where measurements have been practical, matter exhibits wave-like behavior. For example, a beam of electrons can be diffracted just like a beam of light or a water wave.

Example: "An electron (m = 9.11 × 10⁻³¹ kg) accelerated through a potential difference of 100 V acquires kinetic energy KE = eV = 1.6 × 10⁻¹⁷ J, giving a          of λ = h/√(2mKE) ≈ 1.23 × 10⁻¹⁰ m, comparable to atomic spacings."

Decay constant

Quantity that is inversely proportional to the half-life and that is used in equation for number of nuclei as a function of time.

Example: "A radioactive isotope with a half-life of T₁/₂ = 5730 years has a          λ = ln2/T₁/₂ ≈ 1.21 × 10⁻⁴ yr⁻¹, which appears in the exponential decay law N(t) = N₀ e^(−λt) used in carbon-14 dating."

Destructive interference

For example, if at a given instant in time and location along the medium, the crest of one wave meets the crest of a second wave, they will interfere in such a manner as to produce a "super-crest." Similarly, the interference of a trough and a trough interfere constructively to produce a "super-trough." Destructive interference occurs at any location along the medium where the two interfering waves have a displacement in the opposite direction. For example, the interference of a crest with a tro.

Example: "In Young's double-slit experiment,          occurs at positions where the path difference is a half-integer multiple of the wavelength (Δr = (m + ½)λ), producing dark fringes on the screen where the two waves cancel."

Diamagnetic materials

Their magnetic dipoles align oppositely to an applied magnetic field; when the field is removed, the material is unmagnetized.

Example: "Bismuth is a diamagnetic material whose atomic magnetic dipoles align opposite to an applied external field, producing a weak repulsive force that allows bismuth to be levitated above strong permanent magnets in laboratory demonstrations."