According to Huygens Principle, every point on the wavefront AB is the source of secondary wavelets.

Thanks to Ciaran, an 18-year-old from Kelowna, British Columbia, for this question.Fluidmaster duo flush problems atomi smart life Yet, when the same water crystallizes into irregularly packed snow flakes, multiple and diffuse light reflection results in a white surface. It is striking to consider, Livingston adds, how a still pool of water may serve as a poor mirror. These latter examples are turbulent or irregular structures, containing вЂњlots of air,вЂќ which causes вЂњlight reflect off internal and external surfacesвЂќ and scatters the rays of an image. White paint or a piece of paper are classic examples of light scattering, he notes, as are clouds, the foam in your glass of beer, and snow. Surface roughness, Livingston says, also contributes вЂњdiffuse reflection,вЂќ causing the rays of light from different parts of a potential image to вЂњbounce back at different angles.вЂќ Multiple and diffuse reflections scatter the reflecting rays, and all information about the image is lost. Some multiple-reflected light can reemerge from the material surface, but without the same orientation, as that which reflects off a mirror. This allows them to experience multiple reflections from crystal grains and other irregularities within the structure of the surface. White surfaces can reflect a considerable amount of light, but without the mobile electrons to oppose the electric field of light, white surfaces allow light to penetrate up to several wavelengths. Rays of light originating from a personвЂ™s ear, nose, and eyebrow, will вЂњreflect with the same angleвЂќ off a smooth mirror surface and maintain their relative orientation, thus preserving the image that our eyes will perceive. As a result, rays of light bounce вЂњlike tennis balls,вЂќ, always maintaining an angle of reflection to the mirrorвЂ™s surface, that matches in value the raysвЂ™ angle of incidence. In addition, the smoothness of a mirrorвЂ™s glass and metal coating ensure that this surface reflection is specular, says Livingston.

When that occurs, the light has been effectively reflected from the surface of the metal. These mobile вЂњconductionвЂќ electrons are the source of electrical conductivity in metals, and when light attempts to penetrate a metal, they вЂњvibrate in such a wayвЂќ that an opposing electrical field is created, canceling the electric field of light and prohibiting any of its colors from entering beyond a few atomic layers. At the atomic scale, metals are a crystal network of atoms whose outermost electrons dissociate and wander with high mobility through the network.

A mirror is essentially a plate of glass coated with a thin film of metal, such as silver. The answer, Livingston explains, rests in part on the penetration by light. But doesnвЂ™t a mirror also reflect all the colors of light? Why doesnвЂ™t the surface of a mirror appear white, rather than reflecting images into our eyes? White surfaces are composed of molecules or atoms that donвЂ™t absorb any of the visible colors of light our eyes perceive this reflected combination as the color white. The remaining colors penetrate to within a few wavelengths, Livingston says, and partially reflect back. When this spectrum of light falls on a surface, some colors are absorbed by its molecules or atoms. LivingstonвЂ™s color-changing car highlights the fact that light sources, such as the Sun and tungsten filaments, emit a spectrum, or collection, of colors. After driving out onto the city street, with its conventional streetlights, the carвЂ™s color changed back to red. His car thus appeared as black, with a touch of blue. In fact, the street lighting in the lot had been switched to mercury lamps - which, Livingston explains, have almost no red in their light. One evening, walking back to the company parking lot, he was surprised to discover that his car had changed color.

вЂњI used to have a red car, when I worked at General Electric,вЂќ Department of Materials Science and Engineering Senior Lecturer EmeritusВ James LivingstonВ recalls. Why doesnвЂ™t a plain, white piece of paper reflect light, but a mirror does?ДЄlmost everything reflects light - itвЂ™s how it reflects it that makes a differenceвЂ¦ By Sajan Saini

Angle of reflection off a mirror