鏡子的原理(英文)急!!!!

Effects
圖片參考：http://upload.wikimedia.org/wikipedia/en/c/c0/Waves_reflecting_from_a_curved_mirror.PNG
In this diagram plane waves reflect off a parabolic mirror to form waves converging onto a focal point.In a plane mirror, a parallel beam of light changes its direction as a whole, while still remaining parallel; the images formed by a plane mirror are virtual images, of the same size as the original object (see mirror image). There are also concave mirrors, where a parallel beam of light becomes a convergent beam, whose rays intersect in the focus of the mirror. Lastly, there are convex mirrors, where a parallel beam becomes divergent, with the raysappearing to diverge from a common intersection "behind" the mirror.Spherical concave and convex mirrors do not focus parallel rays to asingle point due to spherical aberration. However, the ideal of focusing to a point is a commonly-used approximation. Parabolic reflectorsresolve this, allowing incoming parallel rays (for example, light froma distant star) to be focused to a small spot; almost an ideal point.Parabolic reflectors are not suitable for imaging nearby objectsbecause the light rays are not parallel.
A beam of light reflects off a mirror at an angle of reflection thatis equal to its angle of incidence (if the size of a mirror is muchlarger than the wavelength of light). That is, if the beam of light isshining on a mirror's surface at a 30 angle from vertical, then itreflects from the point of incidence at a 30 angle from vertical inthe opposite direction.
This law mathematically follows from the interference of a plane wave on a flat boundary (of much larger size than the wavelength).