Physics
Motion, waves, fields and the quantum world. 227 topics, from beginner to advanced.
Browse all 227 Physics topics →Featured
Visual showcases to start withTwo-Source Interference
Ripples from two sources create fixed lines of strong and weak waves.
Double-Slit Experiment
Single particles gradually build an interference pattern — evidence of wave–particle duality.
Standing Waves
Waves reflecting on a string create nodes that never move and antinodes that move most.
Doppler Effect
A moving source squeezes wavefronts ahead and stretches them behind, shifting pitch.
Kepler’s Laws of Planetary Motion
Orbits are ellipses with the Sun at one focus, sweeping equal areas in equal times.
Circular Orbits
At exactly the right sideways speed, a falling object keeps missing the planet.
Simple Harmonic Motion
A mass on a spring oscillates sinusoidally with a period set by m and k.
Resonance
Drive an oscillator at its natural frequency and the amplitude grows enormously.
Magnetic Force on Moving Charges
A magnetic force always pushes sideways, so charges travel in circles.
Electric Fields
Field lines leave positive charges and enter negative ones. Drag the charges around.
Thin Lenses
A converging lens focuses parallel rays. Move the object and watch the image change.
Quantum Tunnelling Probability
Barrier penetration falls exponentially with thickness.
Popular
Classic topics most learners start withProjectile Motion
Horizontal and vertical motion are independent: constant vₓ while gravity bends the vertical path.
Free Fall
Without air resistance every object falls with the same acceleration g ≈ 9.8 m/s².
Newton’s Second Law
Net force equals mass times acceleration. In an Atwood machine the heavier mass wins.
Newton’s Third Law
Forces come in equal and opposite pairs: colliding blocks exchange momentum in opposite directions.
Ohm’s Law
Current through a resistor rises in proportion to the voltage across it.
Conservation of Energy
Without friction, kinetic plus potential energy stays constant at every point of the track.
Time Dilation
Moving clocks tick slower; the light-clock thought experiment shows why.
Electromagnetic Waves
Oscillating electric and magnetic fields sustain each other and travel at light speed.
The Photoelectric Effect
Light below a threshold frequency ejects no electrons, however bright — proof that light comes in quanta.
Nuclear Fission
A heavy nucleus splits after absorbing a neutron, releasing energy and more neutrons that sustain a chain reaction.
Refraction and Snell’s Law
Light bends toward the normal when entering a denser medium.
Radioactive Decay
Each atom decays at random, yet the whole sample follows a precise exponential curve.
All 227 Physics topics
🌱 Beginner
- Position, Velocity and Acceleration
- Constant Velocity (Inertia)
- Uniformly Accelerated Motion
- Free Fall
- Projectile Motion
- Range and Launch Angle
- Horizontal Launch from a Cliff
- Newton’s Second Law
- Newton’s Third Law
- Inclined Planes
- Friction
- Normal Force and Weight
- Terminal Velocity
- Uniform Circular Motion
- Centripetal Force
- Torque and Levers
- Pulleys and the Atwood Machine
- Conservation of Momentum
- Elastic Collisions
- Inelastic Collisions
- Impulse and Force over Time
- Work and Energy on a Track
- Conservation of Energy
- Energy Loss to Friction
- Kinetic Energy
- Power
- Simple Harmonic Motion
- Hooke’s Law
- Damped Spring Oscillations
- Resonance
- The Simple Pendulum
- Pendulum Period vs Length
- Kepler’s Laws of Planetary Motion
- Circular Orbits
- Escape Velocity
- Newton’s Law of Gravitation
- Travelling Waves
- Wave Speed, Frequency and Wavelength
- Superposition of Waves
- Constructive and Destructive Interference
- Speed of Sound vs Temperature
- Refraction and Snell’s Law
- Mixing Coloured Light
- Vertical Launch
- Projectile on the Moon
- Constant Deceleration
- Turning Around
- Equal Masses Collide
- Heavy Hits Light
- Steep Ramp
- Rough Ramp
- Balanced Lever with Different Weights
- Unbalanced Lever
- Atwood Machine Nearly Balanced
- Atwood Machine with Big Imbalance
- Slow Circular Motion
- Fast Tight Turn
- Roller Coaster Frictionless
- Roller Coaster with Heavy Friction
- Stiff Spring
- Heavy Mass on a Spring
- Short Pendulum
- Long Pendulum
- Low Orbit
- Elliptical Orbit from Low Speed
- Highly Eccentric Orbit
- Nearly Circular Orbit
- Gravitational Potential Energy
- Orbital Period vs Radius
- Rotational Kinetic Energy
- Moment of Inertia of a Ring and Disk
- Angular Momentum Conservation
- Rolling Without Slipping
- Drag at High Speed
- Kinetic vs Potential Energy over Time
- Centre of Mass Motion
- Mechanical Advantage of a Ramp
- Impulse–Momentum for Airbags
- Coefficient of Restitution and Rebound Height
- Long-Wavelength Wave
- High-Frequency Wave
- Two Waves of Equal Frequency
- Waves Cancelling
- Fundamental Mode of a String
- Sixth Harmonic
- Slow Beats
- Source at Sound Speed
- Wave Speed on a String
- Brewster’s Angle
- Root-Mean-Square Speed
🔧 Intermediate
- Standing Waves
- Harmonics on a String
- Beats
- Sound as a Longitudinal Wave
- Doppler Effect
- Sonic Booms and Mach Cones
- Two-Source Interference
- Seismic Waves
- Decibels and Sound Intensity
- Electromagnetic Waves
- Total Internal Reflection
- Thin Lenses
- The Magnifying Glass
- Concave Mirrors
- Double-Slit Experiment
- Polarisation and Malus’s Law
- Kinetic Theory of Gases
- The Ideal Gas Law
- Boyle’s Law
- Charles’s Law
- Gay-Lussac’s Law
- Newton’s Law of Cooling
- Specific Heat Capacity
- Heating Curve and Phase Changes
- Carnot Efficiency
- Stefan–Boltzmann Law
- Wien’s Displacement Law
- Conduction, Convection and Radiation
- Coulomb’s Law
- Electric Fields
- Ohm’s Law
- Parallel Circuits
- Electrical Power
- RC Circuits and Time Constants
- Inductor Current Growth
- Magnetic Force on Moving Charges
- Magnetic Field Around a Wire
- Faraday’s Law of Induction
- Alternating Current
- Stress on a Spring: Elastic Energy
- Fast Beats
- Low-Pitched Sound Wave
- Loud Sound Wave
- Slow Source Doppler
- Close Double Source
- Wide Double Source
- Nearby Earthquake
- Distant Earthquake
- Intensity and Distance
- Standing Wave Frequencies in a Pipe
- String Frequency vs Tension
- Sound Level of Multiple Sources
- Resonance Curve
- Group vs Phase Velocity
- Lens Maker’s Equation
- Magnification of a Telescope
- Resolution and Aperture
- Thin-Film Interference
- Fresnel Reflection at Normal Incidence
- Inverse Square for Lamps
- Inverse Square Law for Radiation Safety
- Isothermal Expansion
- Adiabatic vs Isothermal Curves
- Thermal Expansion of a Rod
- Heat Conduction Through a Wall
- Cooling Curve of a Mug
- Latent Heat of Melting Ice
- Boltzmann Factor
- Blackbody Peak Shift
- Greenhouse Layer Model
- Phase Diagram of Water
- How a Heat Pump Works
- Capacitor Energy
- Resistance of a Wire
- Resonant Frequency of an LC Circuit
- Impedance of a Capacitor
- Impedance of an Inductor
- Power Factor and Phase Angle
- Magnetic Field Inside a Solenoid
- Induced EMF from a Rotating Coil
- Hall Voltage
- Torricelli’s Law
🚀 Advanced
- Diffusion and Entropy
- Series Circuits
- Transformers
- Electric Motors and Generators
- Lenz’s Law
- The Photoelectric Effect
- Hydrogen Emission Spectrum
- Particle in a Box
- Quantum Superposition
- Radioactive Decay
- Half-Life
- de Broglie Wavelength
- Heisenberg Uncertainty
- Time Dilation
- Lorentz Factor
- Length Contraction
- Mass–Energy Equivalence
- Planck’s Blackbody Curve
- Nuclear Fission
- Nuclear Fusion
- Binding Energy per Nucleon
- Pressure in a Fluid
- Archimedes’ Principle
- Continuity and Bernoulli’s Principle
- Hydraulic Systems
- Maxwell–Boltzmann Distribution
- Heat Engine Efficiency Limit
- Entropy Change on Heating
- The Laws of Thermodynamics
- Capacitance of Parallel Plates
- Charging a Capacitor Through a Resistor
- Maxwell’s Equations in Words
- How a Loudspeaker Works
- How MRI Works
- Wireless Charging
- Lightning Rods
- Rest Energy of Particles
- Relativistic Momentum
- Kinetic Energy in Relativity
- Compton Scattering
- Quantised Energy Levels of Hydrogen
- Quantum Tunnelling Probability
- Activity of a Radioactive Source
- Radioactive Chain Equilibrium
- Shielding and Attenuation
- Radiation Doses in Context
- Particle Masses
- Standard Model Overview
- How a Nuclear Reactor Works
- How GPS Uses Relativity
- Hydrostatic Pressure vs Depth for Water
- Terminal Velocity vs Mass
- Reynolds Number and Flow Regime
- Flow Rate through a Pipe
- Surface Tension and Capillary Rise
Frequently asked questions
What will I learn in Physics?
Motion, waves, fields and the quantum world. Each topic has a live animation, a lesson and a quick quiz.
Where should I start?
Try “Projectile Motion” from the Popular list, or any beginner topic in Browse.
Are the topics in a set order?
Browse groups topics by level, with beginner topics first. Each topic’s FAQ names the topic to read before it.
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