Explain what happens during dark adaptation, including the importance of rhodopsin, how long dark adaptation takes to occur, how it can be wiped out, and how it can be speeded up

What will be an ideal response?

ANSWER: Answer will include that dark adaptation is the dramatic increase in retinal sensitivity to light that occurs after a person enters the dark. It takes about 30 to 35 minutes of complete darkness to reach maximum visual sensitivity. At that point, your eye will be 100,000 times more sensitive to light. The rods contain a light-sensitive visual pigment, rhodopsin, which allows us to see in black and white. When struck by light, visual pigments bleach, or break down chemically. The afterimages one has seen after looking at a flashbulb are a result of this bleaching. In fact, a few seconds of exposure to bright white light can completely wipe out dark adaptation. That's why one should be sure to avoid looking at oncoming headlights when driving at night, especially the new bluish-white xenon lights. To restore light sensitivity, the rhodopsin in the rods must recombine, which takes time. Since the rods are insensitive to extremely red light, submarines, airplane cockpits, and ready rooms for fighter pilots are illuminated with red light, so that these people can move quickly into the dark without having to adapt. Because the red light doesn't stimulate the rods, it is as if these people had already spent time in the dark.