A circular coin of diameter is held face-on (its flat face perpendicular to the line…

PHYSICS · Subjective · Fermi University Physics · Optics & Photonics · Geometrical optics and imaging · Geometrical optics and imaging

Optics and Photonics, Ch Radiometry and photometry

Problem

A circular coin of diameter

2.4\ \mathrm{cm}

is held face-on (its flat face perpendicular to the line of sight) at a distance of

1.2\ \mathrm{m}

from your eye. The coin is small compared with this distance. Find the solid angle the coin subtends at your eye, in steradians.