Visual Python Animations

The animations below with file names ending with the suffix .py are written in the Python programming language with the Visual Python 3D graphics package. Both the Python language and the Visual Python package are open-source software - they are available for free. You can download both from the Visual Python Web site :

http://www.vpython.org

To run an animation, left-click on the animation link in the online lecture notes, and use Save Target As... to save a copy of the code. If you have installed Python and Visual Python, double-clicking on your local copy of the animation code should run it.

• planeWave.py : an animated graph of a traveling harmonic wave
• standingWave.py : an animated graph of a harmonic standing wave (This will only run if the file planeWave.py is present in the same directory.)
• ndBeats.py : an animated graph of the beat pattern resulting from the superposition of two harmonic waves with different frequencies (This will only run if the file planeWave.py is present in the same directory.)
• longTrans.py : compares longitudinal and transverse traveling harmonic waves
• ltStand.py : compares longitudinal and transverse harmonic standing waves
• circularHelical.py : positive charges moving in a uniform magnetic field
• loop.py : forces on the sides of a square loop at various orientations in a uniform magnetic field
• lrc.py : voltages across the inductor, resistor, and capacitor in a series LRC circuit.

I have produced several animated GIF images of optical systems using the POV-Ray ray tracing program. All you need is a web browser to view them.

• A guide to Locating Virtual Images using parallax. Based on animations developed by Luke Sullivan (UC 2007).
• semicylinder.gif : refraction in a semicylindrical lens (animation of the Snell's law lab experiment). As the semicylinder rotates, the pin moves such that its image remains at the center of the semicylinder.
• sphere.gif : refraction/reflection of light from a source behind the observer on a sphere of water (rainbow illustration). The angle between the incident and return rays is displayed.

Some of the animations I use are Java applets called "Physlets" produced by the Web Physics group at Davidson College.

Physlets are embedded in Web pages which you can view with Microsoft Internet Explorer with the Java "Virtual Machine" plugin. You can download the plugin for free from Sun Microsystems :

http://java.com/en/index.jsp

• Doppler Effect : an animation of a source emitting circular wave fronts while moving through a medium
• Electric dipole : an animation of a test charge moving through the electric field produced by an electric dipole
• Four charges with field lines : an interactive figure showing the field lines corresponding to four charges which may be dragged by the user
• Guess the sign : an animation showing a test charge moving through an electric field produced by four charges. The red charge is positive. What is the sign of the test charge?
• A charge in a constant electric field : an animation showing a test charge moving through a constant electric field
• Four charges with equipotential lines : an interactive figure showing the equipotential lines corresponding to four charges which may be dragged by the user. Field vectors are also shown.
• A capacitor with a movable piece of dielectric : drag the dielectric into and out of the capacitor and observe the changes in the electric field (density of equipotential lines) and charge. The potential difference between the plates is held constant.
• Permanent magnets : drag the magnets around and observe the changes in the grid of magnetic field vectors. The colors of the vectors indicate the magnitude of the field.
• Refraction with two Parallel Surfaces : Parallel rays are refracted by two parallel surfaces enclosing a region of larger index of refraction. The position of the source and the angle of the rays can be adjusted by dragging the small circles. Investigate total internal reflection by placing the source between the surfaces.
• Spherical Mirror : Rays from a dragable point source are incident on a spherical mirror.
• Converging Lens : Rays from a dragable point source are incident on a converging lens.