Emmert's law

Emmert's Law says that the perceived size of an afterimage (when you look at something bright and then close your eyes and still see it) depends on how far away you imagine the object to be.

Imagine you're looking at a bright light bulb for a while, then you close your eyes and you still see a faded image of the bulb. Now if you imagine the bulb to be far away, the image will appear smaller in your mind, but if you imagine it to be closer, it will appear larger. This happens because your brain thinks that objects that are far away look smaller and objects that are closer look bigger.

It's sort of like looking at a picture of a big building. If you hold the picture close to your face, the building looks bigger, but if you hold it far away, the building looks smaller.

So, Emmert's Law helps explain how our brain interprets the size of objects in our mind based on how close or far away we imagine them to be.