| w = | pr' .(6) |
| r' ± r |
VI. APPLICATION OF THE FORMULAS TO THE BANDS OF THE ILLUSION.
Will these formulas, now, explain the phenomena which the bands of the illusion actually present in respect to their width?
1. The first phenomenon noticed ([p. 173], No. 1) is that "If the two sectors of the disc are unequal in arc, the bands are unequal in width; and the narrower bands correspond in color to the larger sector. Equal sectors give equally broad bands."
In formula 3, W represents the width of a band, and s the width of the oppositely colored sector. Therefore, if a disc is composed, for example, of a red and a green sector, then
| W(red) = | rs(green) - pr' , |
| r' ± r |
and
| W(green) = | rs(red) - pr' , |
| r' ± r |
therefore, by dividing,
| W(red) | = | rs(green) - pr' . |
| W(green) | rs(red) - pr' |