http://falstad.com/mathphysics.html

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These are some educational applets I wrote to help visualize various
concepts in math, physics, and engineering. They were originally
written in Java, but they've mostly been converted to Javascript, so
you should be able to view them without a Java-capable browser.
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Oscillations and Waves

             Ripple Tank (2-D Waves) Applet
[ripple]     Ripple tank simulation that demonstrates wave motion,
             interference, diffraction, refraction, Doppler effect,
             etc.
[wave2d]     2-D Waves Applet
             Demonstration of wave motion in 2-D.
[wavebox]    3-D Waves Applet
             Demonstration of wave motion in 3-D.
             Coupled Oscillations Applet
[coupled]    Demonstration of longitudinal wave motion in
             oscillators connected by springs.
[dispersion] Dispersion Applet
             Dispersion and group velocity.

Acoustics

[loadedstri] Loaded String Applet
             Simulation of wave motion of a string.
[membrane]   Rectangular Membrane Waves Applet
             Vibrational modes in a 2-d membrane.
             Circular Membrane Waves Applet
[circosc]    Vibrational modes in a 2-d circular membrane (drum
             head).
[barwaves]   Bar Waves Applet
             Bending waves in a bar.
[vowel]      Vowels Applet
             The acoustics of speech.
[modebox]    Box Modes Applet
             Acoustic standing waves in a 3-d box.
[interferen] Acoustic Interference Applet
             Generates audio interference between your speakers.

Signal Processing

[fourier] Fourier Series Applet
          Frequency analysis of periodic functions.
          Digital Filters
[dfilter] Filters digital signals and plays the output on your
          speakers.

Electricity and Magnetism: Statics

            2-D Electrostatics Applet
[emstatic]  Demonstrates static electric fields and steady-state
            current distributions.
            2-D Electrostatic Fields Applet
[vector2de] Demonstrates electric fields in various 2-D situations;
            also shows Gauss's law.
[vector3de] 3-D Electrostatic Fields Applet
            Demonstrates electric fields in various 3-D situations.
[vector3dm] 3-D Magnetostatic Fields Applet
            Demonstrates magnetic fields in various situations.
[motor]     Electric Motor [new]
[motor]     Electric Generator [new]

Electrodynamics

[emwave1]    2-D Electrodynamics Applet (TE)
             Demonstrates electromagnetic radiation.
             2-D Electrodynamics Applet (TM)
[emwave1]    Demonstrates electromagnetic radiation, induction, and
             magnetostatics.
[circuit]    Analog Circuit Simulator Applet
             Demonstrates various electronic circuits.
[circuit]    Analog Filter Applet
             Demonstrates electronic filter circuits.
[embox]      Cavity Modes Applet
             Electromagnetic waves in a 3-d rectangular cavity.
[emguide]    Waveguide Modes Applet
             Electromagnetic waves in a waveguide.
[antenna]    Antenna Applet
             Generates antenna radiation patterns.
[diffractio] Fresnel Diffraction Applet
             Generates Fresnel diffraction patterns.

Quantum Mechanics

             Hydrogen Atom Applet
[qmatom]     Shows the orbitals (wave functions) of the hydrogen
             atom.
             Molecular Orbitals Applet
[qmmo]       Shows the orbitals (wave functions) of the hydrogen
             molecular ion.
             1-D Quantum Mechanics Applet
[qm1d]       Single-particle quantum mechanics states in one
             dimension.
[qm1dcrysta] 1-D Quantum Crystal Applet
             Periodic potentials in one dimension.
[qm2dcrysta] 2-D Quantum Crystal Applet
             Periodic potentials in two dimensions.
             1-D Quantum Transitions Applet
[qm1drad]    Radiative transitions (absorption and stimulated
             emission) in one dimension.
             Atomic Dipole Transitions Applet
[qmatomrad]  Radiative transitions (absorption and stimulated
             emission) in atoms.
             2-D Rectangular Square Well Applet
[qm2dbox]    Rectangular square well (particle in a box) in two
             dimensions.
[qm2dcirc]   2-D Circular Square Well Applet
             Circular square well in two dimensions.
[qm2dosc]    2-D Quantum Harmonic Oscillator Applet
             Harmonic oscillator in two dimensions.
[qmrotator]  Quantum Rigid Rotator Applet
             Particle confined to the surface of a sphere.
[qm3dosc]    3-D Quantum Harmonic Oscillator Applet
             Harmonic oscillator in three dimensions.

Linear Algebra

             Dot Product Applet
[dotproduct] Demonstrates the dot product or scalar product of two
             vectors.
[matrix]     Matrix Applet
             Demonstrates 2-d transformations using a matrix.

Vector Calculus

           2-D Vector Fields Applet
[vector]   Demonstrates various properties of vector fields,
           including divergence and curl, etc.
           3-D Vector Fields Applet
[vector3d] Demonstrates vector fields in 3 dimensions. Includes the
           Lorenz Attractor and Rossler Attractor.

Thermodynamics

[gas]     Gas Molecules Simulation Applet
          Demonstrates the kinetic theory of gases.
[engine]  Heat Engine
          Carnot cycle and other thermodynamic cycles.[new]

Mechanics

[harmonicos] Harmonic Oscillator
             Driving forces, resonance.[new]
[coriolis]   Coriolis Force
             Rotating reference frames.[new]
[foucault]   Foucault Pendulum
             Demonstrates earth's rotation.[new]
             Orbital Rendezvous
[rendezvous] Pilot your ship to meet up with a target ship in a
             different orbit.[new]
[lagrange]   Lagrange Points
             Three-body problem.[new]
[top]        Symmetrical Top
             Rigid body motion of tops and gyroscopes.[new]

Miscellaneous

[diffeq]    Ordinary Differential Equations Applet
            Visual differential equation solver.
            Euler's Equation Applet
[euler]     Demonstrates Taylor series expansion of complex
            exponentials.
[fft]       Discrete Fourier Transform
            Fourier transform in two dimensions.[new]
            Ray Optics Simulation
[rayoptics] A ray optics simulator by Rick Tu and Johnson (with some
            contributions from me)
            Thermal Camera Pictures
[thermal]   Some sample pictures taken with a thermal (infrared)
            camera. (This is not an applet but I thought I'd throw
            it in here anyway.)

Licensing info.

Links to other educational sites with math/physics-related
information or java applets useful for teaching:

  * Lissajous Lab
    based on a Java applet by Ed Hobbs

  * A Complex Mapping Viewer
    another converted Java applet

  * Another Hydrogen Orbital Applet
    WebGL-based.

  * Another Slit Diffraction Applet
    Also here are more applets from Northwestern University.

  * All About Circuits
   
  * MyPhysicsLab Simulations
   
  * Physlets
   
  * 3-D Molecular Dynamics
   
  * Resonata - A Wave Machine
   
  * PhET Interactive Simulations
   
  * All Satellites Currently Orbiting
   
  * a Circuit Diagram maker
   
  * Captured Lightning
   
  * Wondermagnet.com
   
  * Powers of 10 Applet
   
  * Another Fresnel Diffraction Applet
   
  * Acoustics and Vibration Animations
   
  * Earth-Moon Distance
   
  * Finding the Speed of Light with Marshmallows
   
  * Sky Chart
   
  * Errors and Misconceptions
   
  * Sound Lab
   
And when you get tired of learning, here is some fun stuff:

  * Pong Simulation
    Circuit-level simulation of original 1972 Pong.

  * Java Maze Applet
    3d perspective maze.

  * Acorn Envelope Applet
    Cool videogame sounds.

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java@falstad.com