Benham's top
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Benham's top, also called Benham's disk, is named after the English toymaker Charles Benham, who, in 1895, sold a top painted with the pattern shown. See picture (http://faraday.physics.uiowa.edu/optics/6J11.11.htm).
When the disk is spun, arcs of pale color are visible at different places on the disk. These are called called Fechner colors. Not everyone sees the same colors.
The phenomenon is not entirely understood. One possible reason people see colors may be that the color receptors in the human eye respond at different rates to red, green, and blue. Or, more specifically, that the latencies of the centre and the surround mechnisms differ for the different types of color-specific ganglion cells.
External links
- http://faculty.washington.edu/chudler/benham.html
- An interactive version (http://www.michaelbach.de/ot/col_benham/index.html)