The pupil's diameter varies between about in bright sunlight and at full dark adaptation.
PHYSICS · Multi-part · Fermi University Physics · Biophysics & Medical Physics · Bioelectricity, the senses and the physics of the body · Bioelectricity, the senses and the physics of the body
Forces, Machines and Signals, Ch Vision and photoreception: counting photons
Problem
The pupil's diameter varies between about 1.5mm in bright sunlight and 8mm at full dark adaptation.
((a)) Compute the ratio of pupil areas between the widest and narrowest states.
((b)) Express this ratio in decades (powers of ten) of light-gathering power.
((c)) Illumination itself spans about nine decades from starlight to sunlight. What fraction of this total range is covered by pupil constriction alone, and where must the rest of the adaptation occur?