Dear Rootosaurus, when you're looking at an image of a chair behind you in a flat mirror, then you're observing the so-called virtual image of the chair. If the mirror's surface is located in the $x=0$ plane and the coordinate of the real chair is at $(x,y,z)$, then the virtual image of the chair is at $(-x,y,z)$.
However, the light rays coming from the real chair that are reflected by the mirror and that ultimately end up in your eyes have exactly the same directions as the light rays of a hypothetical chair that would be actually located at the point $(-x,y,z)$ behind the mirror. So geometrically, you can't really distinguish a reflection of a chair that seems to be located at $(-x,y,z)$ from a real chair that is located at $(-x,y,z)$ and that you're observing through a window without a mirror. The geometry of the light rays is identical. That's why the concept of images is so useful.
In particular, myopia means that one has some trouble to observe distant objects. Distant objects - imagine a distant point - have the property that they emit light rays that are nearly parallel. The further an object is, the more parallel its light rays look when they arrive to your eye. However, the lenses in your eyes have to convert these parallel mirrors into converging mirrors - so that all the light rays coming from the distant star end up at one point of the retina.
Myopic eyes are good in converting "steeply divergent" light rays from nearby objects to converging ones, but they're doing too much of a good thing. When you get too parallel light rays, myopic eyes make them converge too much, too early - the intersection will be inside the liquid in your eye. Hyperopia is the opposite disorder in which eyes make the light converge less than is needed. But what's relevant for your question is that the virtual image of the chair at $(-x,y,z)$ "emits" the same excessively parallel rays as a real chair at the same point, so a myopic eye will have the same trouble seeing it. After all, it shouldn't be paradoxical: the total distance that the light rays have traveled includes the distance of you from the mirror as well as the distance of the mirror from the real chair - because the colorful photons ultimately came from the chair and they were just reflected, not created, at the plane of the mirror.
Creative thinking with this question.
Rayleigh scattering is the scattering of a plane wave from a single small particle well-separated from other particles. If a second small particle is somewhat nearby, it will scatter coherently with the first and create interference. The far-field will not be Rayleigh anymore; you cannot just add the intensity, the phases also matter.
Say enough small particles aggregate very close together to form a large sphere, with the spacing between particles much less than the wavelength of the light. Then the combined interference effects from each scattering point produce the Mie solution. The idea is nicely illustrated in this method, for example, http://en.wikipedia.org/wiki/Discrete_dipole_approximation. The interference from each discrete dipole slowly builds up to give the scattering from arbitrary scattering-particle shapes. (Mie is for spheres.)
The molecules in a glass of water are separated by a distance much less than the wavelength of the light, so Rayleigh is not applicable. The water is effectively a homogeneous medium with a uniform index of refraction.
Best Answer
The wavelength of light is any wavelength. There's visible light (which is what I think you mean) and then there's every possible wavelength above and below that.
Our eyes don't detect light (electromagnetic radiation) outside of the visible region (hence the name :-)) but we can use and do machines to detect these wavelengths and you've probably experienced them : X-ray machines, UV lights for security purpose, infra-red lights for remote controls.
Whatever wavelength you use is going to diffraction limited for resolution. As this detailed article explains, the limit for resolution (and that's assuming everything else is optimal) is about half the wavelength used.
Optical microscopes are designed for the visible wavelengths of light and focus light outside of this region well. You can use special optics designed for that purpose if your interest is outside of visible light.
The development and use of microscopes, not just visible light microscopes, is called Microscopy. That link should provide you with enough information to start with.
Beyond light microscopes, scientists developed the electron microscope and later the scanning tunneling microscope. The principles of these devices are explained at those links.
The 1986 Nobel prize for Physics was shared between three people for their work on these inventions. Another man, Hans Busch, had made a major contribution to the design of the electron microscope but died in 1984 and the Nobel Prize is never awarded posthumously, so even if the committee had thought it appropriate to award him, the rules would have forbidden it.