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.

## Oscillations and Waves

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

## Acoustics

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

## Signal Processing

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

## Electricity and Magnetism: Statics

 2-D Electrostatics Applet Demonstrates static electric fields and steady-state current distributions. 2-D Electrostatic Fields Applet Demonstrates electric fields in various 2-D situations; also shows Gauss's law. 3-D Electrostatic Fields Applet Demonstrates electric fields in various 3-D situations. 3-D Magnetostatic Fields Applet Demonstrates magnetic fields in various situations.

## Electrodynamics

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

## Quantum Mechanics

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

## Linear Algebra

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

## Vector Calculus

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

## Thermodynamics

 Gas Molecules Simulation Applet Demonstrates the kinetic theory of gases. Thermal Camera Pictures Some sample pictures taken with a thermal (infrared) camera. (This is not an applet but I thought I'd throw it in here anyway.)

## Miscellaneous

 A Sense of Scale Provides a visual comparison of various distances, from very small objects like protons and electrons, to distances between galaxies. (Not an applet, but I thought I'd include it here anyway.) Ordinary Differential Equations Applet Visual differential equation solver. Euler's Equation Applet Demonstrates Taylor series expansion of complex exponentials.

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

And when you get tired of learning, here is some fun stuff: