Dark adaptation may be destroyed in less than a ______.

Dark adaptation may be destroyed in less than a ______.

• A. Second
• B. Minute
• C. A Flash
• D. Hour

Answer: (C)

Dark adaptation is the eye’s increased sensitivity in dim light that comes from regenerating photopigments in the rods (and to a lesser extent cones). A brief bright flash can instantly bleach those pigments, especially rhodopsin in the rods, so the eye loses its night-vision capability the moment the light hits. Because bleaching happens in an instant, dark adaptation can be destroyed in less than a flash. Recovery to dark vision then requires time in darkness for the pigments to rebuild, which takes minutes to tens of minutes depending on the light’s intensity. So the quickest way to wipe out dark adaptation is a flash, rather than any longer duration of light exposure.

Dark adaptation is the eye’s increased sensitivity in dim light that comes from regenerating photopigments in the rods (and to a lesser extent cones). A brief bright flash can instantly bleach those pigments, especially rhodopsin in the rods, so the eye loses its night-vision capability the moment the light hits. Because bleaching happens in an instant, dark adaptation can be destroyed in less than a flash. Recovery to dark vision then requires time in darkness for the pigments to rebuild, which takes minutes to tens of minutes depending on the light’s intensity. So the quickest way to wipe out dark adaptation is a flash, rather than any longer duration of light exposure.