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SomeMichGuy · M
...did you not realize that you get glasses and wear them without corrective lenses? There are people who, for a living, play pretend, and they use alterations to "create a character", and glasses are one prop which is sometimes desired or required, even for those without them. 😉😆
If you want to understand lenses, you could look at the optics section of, say, the older (but more information-packed) [i]Physics[/i] undergraduate text by Halliday & Resnick (it is in Part Two of the 2-part version), or the newer [i]Fundamentals of Physics[/i] by Halliday, Resnick & Walker.
Or just look up the "thin lenses" or the lense maker's equation, which relates the focal length of a lense to the location of the object & image. There is not much to it, but it shows you how real & virtual images work (real ones are those formed by light going through the image, such as images you see through eyeglasses; virtual ones do not, such as, e.g., the image you see in a mirror, which is not actually formed "back there", feet behind the plane of the mirror).
The equation is
[i]1/i + 1/o = 1/f[/i]
where [i]o, i[/i] are the distances to the 'o'bject and 'i'mage, respectively, and [i]f[/i] is the focal length of the lense.
For a mirror, [i]f[/i] -> infinity, so
[i]1/i + 1/o = 0,[/i] or
[i]1/i = -1/o,[/i] so
[i]o = -i[/i]
Since the object distance is real (as you stand in front of the mirror, light actually DOES bounce off you before going toward the mirror),
[i]o > 0[/i]
so the image distance is
[i]i < 0[/i]
and the image is virtual (because no actual light is passing through the image of you which looks like it is "inside" the mirror).
If you want to understand lenses, you could look at the optics section of, say, the older (but more information-packed) [i]Physics[/i] undergraduate text by Halliday & Resnick (it is in Part Two of the 2-part version), or the newer [i]Fundamentals of Physics[/i] by Halliday, Resnick & Walker.
Or just look up the "thin lenses" or the lense maker's equation, which relates the focal length of a lense to the location of the object & image. There is not much to it, but it shows you how real & virtual images work (real ones are those formed by light going through the image, such as images you see through eyeglasses; virtual ones do not, such as, e.g., the image you see in a mirror, which is not actually formed "back there", feet behind the plane of the mirror).
The equation is
[i]1/i + 1/o = 1/f[/i]
where [i]o, i[/i] are the distances to the 'o'bject and 'i'mage, respectively, and [i]f[/i] is the focal length of the lense.
For a mirror, [i]f[/i] -> infinity, so
[i]1/i + 1/o = 0,[/i] or
[i]1/i = -1/o,[/i] so
[i]o = -i[/i]
Since the object distance is real (as you stand in front of the mirror, light actually DOES bounce off you before going toward the mirror),
[i]o > 0[/i]
so the image distance is
[i]i < 0[/i]
and the image is virtual (because no actual light is passing through the image of you which looks like it is "inside" the mirror).