If I’m on my phone and catch a glimpse of my reflection, I can kind of focus (can’t really explain it well) and change my focus from the game/browser or whatever, and my reflection, and back and forth. How is that happening? Does it have a name?
In: Biology
It’s called focussing. Each of your eyes has a lens inside it that can change shape so that only light that had traveled a specific distance is in focus (and all other light is out of focus).
The light from your phone screen started at the screen and traveled to your eyes, a distance of maybe 50cm. So the lenses in your eyes change shape so that only light which has traveled 50cm is in focus.
The light from your face (ie your reflection), starts at your face, travels 50cm to your phone, reflects and travels another 50cm back to your eyes. So to focus on your face in a reflection, your lenses must change shape to focus only on light that has traveled 1m.
For this reason, your eyes can focus on the screen (50cm) or your reflection (1m), but not both. The lenses in your eyes physically changing shape between these two settings is the visual ability you are perceiving.
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