Wolfram Demonstrations Project

13,000+ Open Interactive Demonstrations
Powered by Notebook Technology »

Retrograde Motion Illusion for an Electric Fan

Initializing live version
Download to Desktop

Requires a Wolfram Notebook System

Interact on desktop, mobile and cloud with the free Wolfram Player or other Wolfram Language products.

This Demonstration shows the rotation of an electric fan in slow motion—by about a factor of 10—for computer display compatibility. The fan rotates clockwise. A conventional incandescent light source is somewhat stroboscopic, due to the 60-cycle alternating current powering it.

[more]

Certain combinations of rotation rate and strobe frequency produce the illusion of retrograde motion, with the fan apparently turning counterclockwise. If the two frequencies are appropriately in synch, the fan can even appear to be motionless.

[less]

Contributed by: S. M. Blinder (March 2011)
Open content licensed under CC BY-NC-SA

Snapshots

Details

Snapshot 1: At relatively low RPM, see clockwise rotation.

Snapshot 2: Speeding up rotation, get retrograde illusion.

Embed Code

Take advantage of the Wolfram Notebook Emebedder for the recommended user experience.

Related Demonstrations More by Author
Browse all topics
Feedback (field required)
Email (field required) Name
Occupation Organization
Note: Your message & contact information may be shared with the author of any specific Demonstration for which you give feedback.
Send