Concept Lab · Reference

Concept Lab Glossary

Every term the simulations use, defined in one or two lines. Each lab's “Learn more” panel links straight to the terms on that page.

Last updated: 26 October 2026

Direct answer

Learn a term here, then see it move in a simulation.

Definitions follow NCERT usage and the standard JEE sign conventions. Formulas are given in the form you will use in a numerical.

Physics

Physics terms

Amplitude: The largest displacement from the mean position in an oscillation or wave.
Angular frequency (ω): 2π times the frequency; ω = 2π/T, measured in rad/s.
Angular momentum (L): For a rigid body L = Iω. It stays constant when no external torque acts.
Brewster angle: The angle of incidence at which reflected light is completely polarised; tan θ_B = n.
Capacitance: Charge stored per volt, C = Q/V, measured in farad (F).
Coherent sources: Sources with a constant phase difference and the same frequency; needed for a steady interference pattern.
Common perpendicular: The segment perpendicular to two skew lines; its length is the shortest distance between them.
Cyclotron frequency: f = qB/(2πm): how often a charge circles in a magnetic field. It does not depend on speed.
Dipole moment (p): For two charges ±q a distance d apart, p = q·d, pointing from −q to +q.
Drift velocity: The small average velocity of electrons along a wire when a current flows; also the E × B drift of a charge in crossed fields.
Electric field (E): Force per unit positive charge, E = F/q, in N/C or V/m.
Electric flux (Φ): Field lines through a surface, Φ = ∮E·dA. For a closed surface Φ = q_enclosed/ε₀ (Gauss's law).
End correction: The extra length (about 0.3 × diameter) added to an open pipe end because the antinode forms just outside it.
Equipotential surface: A surface on which the potential is the same everywhere. Field lines cross it at 90°, and no work is done moving a charge along it.
Escape speed: The least launch speed to leave a planet's gravity for good: v_e = √(2GM/R), about 11.2 km/s for Earth.
Field line: A curve whose tangent gives the field's direction. Lines are crowded where the field is strong and never cross.
Focal length (f): Distance from the pole or optical centre to the principal focus. For a mirror f = R/2.
Fringe width (β): Distance between neighbouring bright (or dark) fringes; β = λD/d in Young's double slit.
Gaussian surface: An imaginary closed surface used to apply Gauss's law.
Geostationary orbit: An equatorial orbit about 35 786 km high with a 24-hour period, so the satellite stays over one spot.
Least count: The smallest measurement an instrument can make, e.g. 1 MSD − 1 VSD for a vernier caliper.
Magnetic field (B): Measured in tesla (T). A charge q moving with velocity v feels F = q(v × B).
Magnification (m): Image height ÷ object height. For a lens m = v/u, for a mirror m = −v/u.
Malus's law: Intensity through an analyser at angle θ to the polarisation: I = I₀cos²θ.
Moment of inertia (I): Rotational inertia, I = Σmr². It depends on the axis chosen.
Null point: The jockey position on a metre bridge or potentiometer where the galvanometer shows no current.
Orbital speed: Speed for a circular orbit at radius r: v = √(GM/r).
Parallel axis theorem: I = I_cm + Md², for an axis parallel to one through the centre of mass at distance d.
Perpendicular axis theorem: For a flat body, I_z = I_x + I_y, where x and y lie in the plane and z is perpendicular.
Phase difference: How far one oscillation is ahead of another, in radians; a path difference Δx gives a phase difference 2πΔx/λ.
Pitch (of a helix): Distance moved along B in one revolution: p = v∥·T.
Polariser: A sheet that lets through light vibrating in one direction only (its transmission axis).
Potential (V): Work done per unit charge to bring a test charge from infinity, in volt; V = kq/r for a point charge.
Precession: The slow turning of a spinning body's axis when a torque acts on it; Ω = τ/L.
Radius of gyration (k): The distance at which all the mass could be placed to give the same I: I = Mk².
Range (projectile): Horizontal distance travelled; R = u² sin 2θ / g without air resistance.
Resonance: Large response when a system is driven at its natural frequency.
Right-hand thumb rule: Thumb along the current, fingers curl in the direction of the magnetic field around it.
Solenoid: A long coil. Inside it B = μ₀nI is nearly uniform; at each end it is half that.
Torque (τ): Turning effect of a force, τ = r × F, in N·m.
Wavefront: A surface on which all points vibrate in the same phase.
Zero error: The reading an instrument shows when it should read zero; subtract it from every reading.

Chemistry

Chemistry terms

Angular node: A plane or cone through the nucleus where ψ = 0; an orbital has l angular nodes.
Antibonding orbital: A molecular orbital with a node between the nuclei; electrons in it weaken the bond.
Bond order: (Bonding electrons − antibonding electrons)/2. Higher bond order means a shorter, stronger bond.
Bonding orbital: A molecular orbital that concentrates electron density between the nuclei and lowers the energy.
CFSE: Crystal field stabilisation energy: the energy gained by placing d electrons in split d levels.
Chiral centre: A carbon (or other atom) bonded to four different groups; the molecule then has a non-superimposable mirror image.
CIP priority: Cahn–Ingold–Prelog rules: higher atomic number at the first point of difference gets higher priority.
cis / trans: Like groups on the same side (cis, 90° in complexes) or opposite sides (trans, 180°).
Conformation: A shape reached by rotating about a single bond, e.g. staggered and eclipsed ethane.
Coordination number: The number of nearest neighbours of an atom or ion in a crystal, or ligand atoms bonded to a metal.
Dihedral angle: The angle between two planes; in a Newman projection, the angle between groups on the front and back carbons.
Enantiomers: Non-superimposable mirror-image molecules; they rotate plane-polarised light equally in opposite directions.
fac / mer: In MA₃B₃ complexes: three like ligands on one face (fac) or along a meridian (mer).
Hybridisation: Mixing atomic orbitals of one atom to form equivalent hybrid orbitals, e.g. sp³ from one s and three p.
Lone pair: A pair of valence electrons not used in bonding; it repels more strongly than a bond pair.
Newman projection: A view straight down a C–C bond: the front carbon is a point, the back carbon a circle.
Octahedral void: A gap surrounded by six spheres; a ccp lattice has as many as there are atoms.
Packing fraction: Fraction of the unit cell volume filled by atoms: 52.4% SC, 68% BCC, 74% FCC and HCP.
Paramagnetic: Attracted into a magnetic field because of unpaired electrons, e.g. O₂.
R / S configuration: The label of a chiral centre: with the lowest priority group away, 1 → 2 → 3 clockwise is R, anticlockwise S.
Radial node: A spherical shell where ψ = 0; an orbital has n − l − 1 radial nodes.
Radius ratio: r⁺/r⁻ for an ionic solid; it predicts the coordination number of the cation.
Spin-only magnetic moment: μ = √(n(n + 2)) BM, where n is the number of unpaired electrons.
Tetrahedral void: A gap surrounded by four spheres; a ccp lattice has twice as many as there are atoms.
Unit cell: The smallest repeating box that builds the whole crystal by translation.
VSEPR theory: Electron domains around an atom arrange themselves as far apart as possible, which sets the shape.
Δo (crystal field splitting): The energy gap between eg and t2g in an octahedral field; Δt ≈ (4/9)Δo for tetrahedral.

Maths

Maths terms

Cross product (a × b): A vector perpendicular to a and b with length |a||b|sin θ, the area of their parallelogram.
Direction ratios: Any three numbers proportional to a line's direction cosines, e.g. (a, b, c) for a normal.
Disc method: Volume of a solid formed by rotating y = f(x) about the x-axis: V = π∫y² dx.
Dot product (a · b): a₁b₁ + a₂b₂ + a₃b₃ = |a||b|cos θ; zero when the vectors are perpendicular.
Eccentricity (e): Distance to the focus ÷ distance to the directrix: 0 for a circle, < 1 ellipse, 1 parabola, > 1 hyperbola.
Foot of the perpendicular: Where the perpendicular from a point meets a line or plane.
Generator (of a cone): A straight line on the cone's surface through its vertex.
Image of a point: The mirror point on the other side of a plane; the foot of the perpendicular is the midpoint.
Limit along a path: The value f approaches as (x, y) moves toward a point along one curve. A two-variable limit exists only if all paths agree.
Normal vector: A vector perpendicular to a plane; for ax + by + cz = d it is (a, b, c).
Removable discontinuity: A point where the limit exists but f is undefined or has a different value.
Saddle point: A point that is a maximum in one direction and a minimum in another, like the middle of z = x² − y².
Scalar triple product [a b c]: (a × b)·c, the volume of the parallelepiped on a, b, c; zero when they are coplanar.
Shell method: Volume when rotating about the y-axis: V = 2π∫x·f(x) dx.
Skew lines: Lines in space that are neither parallel nor intersecting.

FAQs

Frequently asked questions

Where do these definitions come from?

They follow the NCERT textbooks and standard JEE usage, written short enough to revise in one pass.

How do I use the glossary with the labs?

Open any lab; its Learn more panel shows the terms used on that page, each linking to its definition here.