What term describes the angle-dependent absorption of light by cones?

• A. Stiles-Crawford effect
• B. Directional sensitivity
• C. Spectral sensitivity
• D. Luminance sensitivity

Answer: (B)

The angle-dependent absorption by cones is described by the Stiles-Crawford effect. Cones act like tiny optical waveguides, so light entering near the center of the pupil and along the cone’s axis is absorbed more efficiently than light that enters obliquely. This directional sensitivity means the same light can produce different responses depending on where it hits the pupil, a phenomenon especially strong in cones and important for understanding brightness perception for small, localized sources. Spectral sensitivity is about wavelength-response, luminance sensitivity refers to overall brightness, and directional sensitivity is a more general term that doesn’t capture this specific retinal mechanism.