Lets say you are near sighted. Your face is 5 inches away from a mirror in front you. But when you try to look at something far behind you through the mirror, it looks as if it were actually very far from you (blurry), even though the image you are seeing is just 5 inches away from you.
Posted Jul 25, 2012, 6:02 PM UTC
The mirror is only 5 inches away from you, but the source of the image is not -- a plane mirror will reflect the incoming light at the same angle as it comes in at, effectively making a "virtual" source the same distance away from the plane, but behind it. If the mirror were curved slightly, this would have a distorting effect similar to glasses or contacts that would possibly allow you to see the images in focus.
The image on a mirror is not 'right in front of you'. It's not a picture, it's a reflection. If you look at a reflection of something 10 feet away, your eyes need to focus to a distance of 10 feet.
So, what you are actually "seeing" is the light reflected from that object. If you track the path of that light, it is traveling that far distance, then reflecting off the mirror to your eye. So the object is actually appears 5 inchs further than it would if you were facing it directly (assuming that the mirror is not focusing or refracting the light) Near sighted vs far sighted, is the ability of your eye's lens to focus that light onto the back of your eye. If the focal point of the lens in your eye is not actually lined up with the back of your eye, then objects appear blurry.
Wow, I've been wondering this for a while, never thought it would be such a simple and easy to understand answer. Thanks :D