Where light falls: diagrams of illumination
Ray diagrams over squares comparing an adversary's claim with what experience shows
Three ink diagrams study how light spreads from a source across a surface, with numbered scales along the edges of squares tracking rays that fan from an aperture or lamp. The note contrasts the adversary's claim — that the long light a b would strike only the point c — with what experience shows, namely that it illuminates the interval d e. A further figure divides the field into a part belonging to the adversary (a b f i K) and a part that is 'mine' (a b c g h).
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Where the light a b actually falls: c versus d e
According to the adversary, the long light a b would illuminate only at the point c. But experience illuminates at d e. The numbered scales along the square measure how far the light reaches.
The adversary's region and mine
The illuminated field is partitioned by letters: a b f i K is assigned to the adversary, while a b c g h is 'mine'. The competing claims are set against one another over the same ray diagram.