I have a wifi router in my room and it has some LEDs, the instant I switch off the lights I almost can’t see anything but in a while the same room gets more visible.
It’s just an example and it happens to everyone, but how does it work? How do our eyes adjust to it, does our eyesight get better? The photons that reflect in our eyes would be the same right? Maybe our eyes (try to) create/sketch the room, based on how it gets the input?
How does this happen?
In: Physics
Pupils work like a camera’s aperture. In low light conditions, they dilate (get bigger) to let in more light, making it easier to see in the dark. When there’s lots of light, they get smaller to avoid letting in too much light which causes a few various problems.
There’s also some rod cell shenanigans going on, but the pupils are the main point.
2 reasons.
First is your pupils dilate, letting more light in.
Second is that “seeing” actually involves your eye using up its light sensitive chemicals. That’s why a bright flash can blind you for a moment, and why a bright light will leave a dark spot in your vision.
While you’re in a bright environment these chemicals are being used up fast. Especially your more sensitive rod cells, which because they are so sensitive get completely washed out in bright light. Once you move into a dark environment it might take several hours for your rod cells to completely refill themselves with those light sensitive chemicals and reach their full sensitivity.
You ever notice how your pupils will sometimes be bigger and sometimes smaller? That’s precisely how.
Your pupils are where light enters your eyes, and they’re likewise your eyes’ main defense against light-induced damage; by expanding and contracting, they allow more or less light into your eyes, which for one part affects how much light you need to see and for another helps alleviate stronger lighting from causing permanent damage.
When in a well-lit room, your pupils are contracted, they’re smaller and letting less light in, enough that you can see just fine, but not enough that it will harm your eyes. When you turn those lights off and the room gets dark, your pupils begin expanding.
However, that change isn’t instant, in an extreme change such as bright to dark in a split second as we see with turning lights on and off, it can still take a few minutes for your eyes to adjust. At the beginning everything will seem near pitch black because your eyes were adjusted to light, over time it gradually shifts, and eventually your eyes are completely adjusted, by which point you’ll see much clearer.
It’s likewise why your eyes may sometimes hurt when waking up in the morning; your eyes were adjusted to the pitch black of your eyelids and are suddenly cast back into light, then need to take a couple minutes to readjust.
Additionally, you can also see the difference in action; find a dark room, turn the light on, completely cover one eye for a couple minutes, then turn the light off and uncover your eye. Your uncovered eye will have adjusted to the light and thus will see very little in the dark, while your covered eye will be adjusted for the darkness and see everything much clearer.
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