Will a patient perceive the red image or the green image to be clearer if they are fogged?

• A. Red image
• B. Green image
• C. Both equally
• D. Neither

Answer: (A)

Fogging acts like a scattering medium, diffusing light and reducing image contrast. Light of shorter wavelengths (like green) is scattered more efficiently by the tiny droplets in fog than longer wavelengths (red). This means the green component of the image loses more contrast and detail than the red component as they pass through the fog. With the red light suffering less scattering, the red image retains more sharpness and perceived contrast, so it appears clearer than the green. In very dense fog, both degrade, but the red image still tends to be clearer than the green one.