Constants & Key Values

Maximum speed in the universe. Exact value defines the metre.

Quantum of action. Appears in E = hf and de Broglie wavelength λ = h/p.

Used in quantum mechanics: E = ℏω, angular momentum quantisation.

Appears in Newton's law of gravitation: F = Gm₁m₂/r².

Standard value at Earth's surface. JEE problems typically use g = 10 m/s² unless stated otherwise.

Charge of a proton (and magnitude of charge of an electron). Fundamental unit of charge.

Rest mass of the electron.

Rest mass of the proton. Nearly equal to the mass of a neutron.

Slightly heavier than the proton.

1/12 the mass of a carbon-12 atom. Used in nuclear mass calculations.

Number of particles in one mole of any substance.

Relates thermal energy to temperature: average KE per degree of freedom = ½k_BT.

R = Nₐ × kB. Appears in ideal gas law PV = nRT.

Radiated power per unit area: P = σT⁴ for a black body.

Appears in Coulomb's law and capacitance formulas.

The standard JEE value. Memorise as 9 × 10⁹.

Appears in Biot-Savart law and Ampere's law.

Fundamental relation connecting electromagnetism and optics.

Radius of the first orbit in the hydrogen atom (Bohr model).

Energy gained by an electron through 1 volt potential difference. Standard unit in atomic/nuclear physics.

Used in nuclear binding energy and particle physics problems.

Appears in hydrogen spectrum: 1/λ = R∞(1/n₁² − 1/n₂²).

Ground state energy = −13.6 eV. Ionisation energy from ground state = 13.6 eV.

Used in satellite orbit and escape velocity problems.

Mean radius. Used in g-variation with altitude and depth problems.

Minimum speed to escape Earth's gravity from the surface.

Used in planetary orbit and Kepler's law problems.

Mean Earth–Sun distance.

Standard conditions for gas law problems.

One mole of any ideal gas occupies 22.4 litres at STP.

Lowest possible temperature. Molecular kinetic energy is minimum (not zero in quantum mechanics).

Varies with temperature: v ∝ √T. Used in resonance, Doppler effect problems.

Refractive index n = c/v. Water: n ≈ 1.33, Glass: n ≈ 1.5.

VIBGYOR: Violet 400–450 nm, Indigo 450–470 nm, Blue 470–500 nm, Green 500–560 nm, Yellow 560–590 nm, Orange 590–620 nm, Red 620–700 nm.