Home Wikituition Browse all terms Categories
Random term

Terms starting with R

49 terms · page 1 of 3

A–Z
All A B C D E F G H I J K L M N O P Q R S T U V W X Y Z
Filtering by: Starts with R Clear all
Biophysics & Medical Physics

Radiation Dosimetry

The subfield of medical physics quantifying and measuring ionizing radiation energy deposited in human tissues or phantom materials.

D = dĒ / dm (Absorbed Energy per Unit Mass) Gy (Gray = J/kg) Geophysics & Environmental Physics

Radiative Forcing

The net change in Earth's energy balance per unit area at the tropopause due to an environmental driver of climate change.

ΔF = F_incoming - F_outgoing W/m² (Watts per square meter) Nuclear & Particle Physics

Radioactive Decay

The spontaneous process by which an unstable atomic nucleus loses energy by emitting ionizing radiation (particles or electromagnetic rays).

N(t) = N₀ e^(-λ t), A(t) = λ N(t) Bq (Bequerels = decays/s) or Ci (Curies) Nuclear & Particle Physics

Radioactive Tracer

A chemical compound containing a radioisotope used to trace chemical or biological pathways through living organisms or industrial systems.

A(t) = A₀ e^(-λ t) (Short half-life diagnostic radiopharmaceutical) MBq or mCi (Administered Activity) Biophysics & Medical Physics

Radiobiology

The study of the biological mechanisms and health effects of ionizing radiation acting on living cells and biological tissues.

DNA Double-Strand Breaks (DSB) ~ 35–40 per Gy per Cell Gy (Dose Response Units) Nuclear & Particle Physics

Radiocarbon Dating

A radiometric dating method that measures the residual decay activity of Carbon-14 in organic materials to determine their age up to…

t = -(t_½ / ln 2) ln(A(t) / A₀), t_½ = 5730 years Years Before Present (BP) Plasma Physics

Radiofrequency Plasma Heating

A method of heating fusion plasma by launching high-power electromagnetic waves tuned to particle cyclotron or hybrid resonance frequencies.

Resonance Matching: ω_wave = ω_ce (ECRH) or ω_wave = n ω_ci (ICRH) MW (RF Power Input) Geophysics & Environmental Physics

Radiometric Dating in Geology

A geochronological technique used to determine the absolute age of rocks and minerals by measuring radioisotope parent-to-daughter ratios.

t = (1 / λ) ln(1 + D / P) (Parent P → Daughter D) Ma or Ga (Millions / Billions of Years) Biophysics & Medical Physics

Radiopharmaceuticals

Pharmaceutical compounds containing radioactive isotopes administered to patients for target-specific diagnostic imaging or therapy.

Targeted Radionuclide Compound: Radiotracer + Carrier Molecule MBq or mCi (Administered Activity) Biophysics & Medical Physics

Radiotherapy

The clinical treatment of malignant cancer tumors using precisely targeted ionizing radiation beams to induce double-strand DNA damage in…

Linear-Quadratic Cell Survival: S = exp(-α D - β D²) Gy (Gray = J/kg) Total Prescribed Dose Classical Mechanics

Radius of Gyration

The radial distance from a rotation axis at which total mass could be concentrated without altering the moment of inertia.

k = √(I / m) m Geophysics & Environmental Physics

Radon Gas Migration

The environmental migration of radioactive Radon-222 gas from decaying uranium in rocks and soil into indoor building spaces.

Decay Chain: ²³⁸U → ²²⁶Ra → ²²²Rn (Half-life = 3.82 days) Bq/m³ or pCi/L (Activity Concentration) Optics

Rainbow Formation

An optical meteorological phenomenon caused by reflection, refraction, and chromatic dispersion of sunlight inside raindrops.

θ_primary ≈ 42° (Red outer, violet inner) Degrees (°) Foundations of Physics

Random Error

Unpredictable, non-repeatable fluctuations in experimental measurements that occur with equal probability in either direction.

Standard Error = σ / √N Various Classical Mechanics

Range

The total horizontal distance traveled by a projectile from launch to landing at the same vertical height.

R = (v0² sin 2θ) / g m Optics

Rayleigh Criterion

The condition for two point sources to be barely resolved by an optical instrument, stating that the central diffraction maximum of one…

θ_min = 1.22 λ / D rad (radians) Optics

Rayleigh Scattering

The elastic scattering of light or electromagnetic radiation by particles much smaller than the light's wavelength.

I_scattered ∝ 1 / λ⁴ W/m² Electromagnetism & Electronics

RC Circuit & Time Constant

An electrical circuit composed of resistors and capacitors driven by a voltage source, characterized by its exponential charging and…

V(t) = V₀ e^(-t / τ), τ = R C s (Seconds) Optics

Real Image

An optical image formed by actual convergence of light rays, which can be projected onto a physical screen.

v > 0 (for real image), m < 0 (inverted) m Condensed Matter & Materials Physics

Reciprocal Lattice

The Fourier transform space of a real-space crystal lattice, where every point corresponds to a set of parallel lattice planes in the real…

b₁ = 2π (a₂ × a₃) / (a₁ · (a₂ × a₃)), G · R = 2π n m⁻¹ (Reciprocal Distance) Astrophysics, Cosmology & Relativity

Red Giant

A large, luminous star in a late evolutionary stage that has exhausted core hydrogen fuel and expanded its outer envelope.

Radius R ~ 10–100 R_☉, T_surface ~ 3,000–4,500 K Solar Radii (R_☉) & Kelvin Optics

Reflection

The bouncing back of a light ray or wave when it strikes a boundary surface between two different media without entering the second medium.

θ_i = θ_r Degrees (°) Optics

Refraction

The bending of a light ray as it passes obliquely from one transparent medium into another with a different refractive index.

n1 sin θ1 = n2 sin θ2 (Snell's Law) Dimensionless (n) Thermodynamics & Statistical Physics

Refrigerator / Heat Pump

A thermodynamic device operating in reverse that consumes mechanical work to extract heat from a cold region and reject it into a warmer…

COP_ref = Q_cold / W, COP_hp = Q_hot / W Dimensionless (Coefficient of Performance)