Hi David - I have a question I think only you can answer. There's something that's really confusing me:
Alright, so I have a mirror set up in my room and it reflects the other end of the room which is about 14 feet away. When I stand in front of this mirror at about 1 foot from it and look at the reflection, I automatically 'assume' that what I am looking at is actually 14 feet away from me. Therefore, the objects in the reflection are blurry. It occurred to me yesterday that I am straining to see something that I believe to be 14 feet away and therefore mis-focusing on what is actually only 1 foot away from me. Am I correct to think that what is 'on' the mirror is 2-dimensional and at a single distance of 1 foot? Which would mean that if I focus on the mirror as it's own object - as though it were a painting 1 foot away from me - everything it reflects would be clear? I'm so confused because I tried to look at the mirror this way and things started to clear up for me but then I overthought the whole thing and lost it. I'm sure you'd like to tell me to stop thinking about it and just look at it, but honestly I feel like I have a habitual distance-gauge which refuses to let me see something at 1foot that I "know" to be 14 feet away from me. :-\
I could be wrong, but I think that the purpose of a mirror is to reflect light rays. Due to the reflections of the rays off of the mirror, the light enters your eyes as if the objects in question were actually "behind" the mirror. Therefore, I don't think it's unreasonable to treat looking in the mirror the same as if you were looking at the object itself. At least theoretically, there is no difference between seeing an object fourteen feet from you and looking at a mirror image of an object fourteen feet behind you. So I think the idea of focusing still applies here. Unless I'm much mistaken, it is the light rays that are focused, not the actual object itself.
@David: Thanks for pointing that out. I did not consider the intensity of light in my explanation. Mirrors that are "perfectly" flat, and therefore perfectly reflective are very, very rare, and so most mirrors (and lenses too) will "lose" some of the light (in the case of mirrors, some light is transmitted into them; in the case of lenses, some light is reflected and never reaches the eye) and the resulting image is not as intense (or as "sharp") as the actual object. But if I'm not mistaken, the difference is greater in lenses (like glasses) than in the average mirror, which tends to reflect light pretty well.
Dr. Bates relates the expirements by which he disproved commonly held theories on the operation of the eye in Perfect Sight Without Glasses and one of the things he did involved a contraption where the subject would look at a coin 6" or so front of the face, and a mirror adjusted to read a Snellen chart at 20' behind via a mirror, like David stated. So, technically, the object is in the distance, however experimentation is highly encouraged if you are so inclined.