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The seven colors in Newton's optical spectrum (red, orange,
yellow, green, blue, indigo and violet) may be recombined in a number of ways,
including the seven-mirror
device and the oscillating
prism. Newton himself suggested the use of the color wheel, in which wedges
of paper with the seven colors on them are pasted onto the surface of a rotating
wheel. Normally a number of complete sets of colors are present.
When the disk is rotated, the colors blur together and the eye, unable to respond rapidly enough, sees the colors mixed together to form white. Since the eye is more sensitive to colors in the middle of the visible spectrum, the wedges with yellow and green are often made narrower, while those for red and violet are made wider. This example by W.& S. Jones of London is at Transylvania University in Lexington, Kentucky. |
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Also at Transylvania is this Color Top. Originally, the upper surface of the spinning top had wedges of colored paper glued to its top. |
| The Newton's Disk on the left-hand side appeared on a eBay
auction in November 2000. It has an overall height of 65 cm, and the diameter
of the disk is 31 cm. Note that the drive belt is missing.
On the right-hand side is a wheel from Kenyon College, mounted on an unmarked rotator made ca. 1900. This was probably a home-built adaptation of another piece of apparatus, as the colored wedges are glued to the surface of a siren disk. The disk also has teeth around its edge, making it possible to use it as Savart's wheel. |
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The blurring of the colors can be seen by the entire class
if the color disk is made transparent and mounted on a lantern slide.
The upper example is from the Virginia Military Institute in Lexington, Virginia, and lower one is in the collection of the National Museum of American History at the Smithsonian Institution. Neither one has a maker's mark. REF: Thomas B. Greenslade, Jr., "Spectrum Recombination", Phys. Teach., 22, 105-108 (1984) |
| The electrically-driven color wheel apparatus is in the Kenyon College apparatus collection. I can personally vouch for the fact that it has not been used since 1964! This is probably a mistake, although the modern physics curriculum rarely has time for discussions of color. It is listed in the 1929 Chicago Apparatus Co. catalogue as "Color Top, Electric. Will run at high speed for hours. Four color disks are furnished... $1.75" The small electric motor is by the K.D. Company, and bears the patent date of April 9, 1901. The solid-color disks are slotted, and my be overlapped, as in the case of the black/white and red/blue disks at the left. The concentric and conjoined disks may then be slid around to vary the relative amount of each color. Three disks can also be put together to produce the illusion of white when they are spinning. |
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