why do things look dark after you stare at something bright (like a lightbulb)?
In: Biology
There are two reasons why. First, the iris, the coloured part of your eyes, will expand or contract to make a different sized opening based on the amount of light available. Our vision works best with a certain amount of light getting into our eyes, with too much or too little not working as well, which is why we have this feature to control the amount of light that gets into our eyes. You can see this in a mirror, if you have a light source you can switch on and off and a mirror you can put your face close to. [A page that describes this in more detail.](https://learning-center.homesciencetools.com/article/eye-and-vision/)
Second, the layer of cells at the back of your eye in the retina, which the light hits, will sort of “get used to,” or “get stuck” based on what they are seeing. It takes them a short time to recover back to normal. [This causes an afterimage, which you can see by looking at very bright colours or lights for a time and then looking away.](https://faculty.washington.edu/chudler/after.html)
Latest Answers