In photopic conditions, if light enters the pupil through the center to reach the retina, does the light appear brighter or dimmer?

• A. Dimmer
• B. The brightness is the same
• C. It depends on pupil size
• D. Brighter

Answer: (D)

Under photopic vision, brightness is determined by how much light actually reaches and stimulates the cones, especially in the fovea. When light travels along the eye’s optical axis and enters through the center of the pupil, it follows a direct path with fewer optical distortions, so more of the incoming light is focused onto the central retina. This increases retinal irradiance and makes the image appear brighter. If light enters toward the edge of the pupil, oblique angles and peripheral aberrations can spread or reduce the energy reaching the fovea, which can diminish perceived brightness. So, light entering through the center tends to look brighter.