In the most general case, a certain fraction of the light is reflected from the interface, and the remainder is refracted. In fact, reflection of light may occur whenever light travels from a medium of a given refractive index into a medium with a different refractive index. The law of reflection states that θ i = θ r, or in other words, the angle of incidence equals the angle of reflection. By projecting an imaginary line through point O perpendicular to the mirror, known as the normal, we can measure the angle of incidence, θ i and the angle of reflection, θ r. In the diagram, a light ray PO strikes a vertical mirror at point O, and the reflected ray is OQ. Reflection also occurs at the surface of transparent media, such as water or glass. Reflection is enhanced in metals by suppression of wave propagation beyond their skin depths. Ī mirror provides the most common model for specular light reflection, and typically consists of a glass sheet with a metallic coating where the significant reflection occurs. In specular reflection the phase of the reflected waves depends on the choice of the origin of coordinates, but the relative phase between s and p (TE and TM) polarizations is fixed by the properties of the media and of the interface between them. Reflection of light is either specular (mirror-like) or diffuse (retaining the energy, but losing the image) depending on the nature of the interface. Even hard X-rays and gamma rays can be reflected at shallow angles with special "grazing" mirrors. Reflection of VHF and higher frequencies is important for radio transmission and for radar. Reflection is observed with many types of electromagnetic wave, besides visible light. Reflection is observed with surface waves in bodies of water. In geology, it is important in the study of seismic waves. In acoustics, reflection causes echoes and is used in sonar. The law of reflection says that for specular reflection (for example at a mirror) the angle at which the wave is incident on the surface equals the angle at which it is reflected. Common examples include the reflection of light, sound and water waves. Reflection is the change in direction of a wavefront at an interface between two different media so that the wavefront returns into the medium from which it originated. Figure 6.The reflection of Mount Hood in Mirror Lake Another use is in periscopes found in submarines. One use of these perfect mirrors is in binoculars, as shown in Figure 6. If, as shown in the figure, the index of refraction for the second medium is less than for the first, the ray bends away from the perpendicular. Part of the light crosses the boundary and is refracted the rest is reflected. Interestingly, we can produce total reflection using an aspect of refraction.Ĭonsider what happens when a ray of light strikes the surface between two materials, such as is shown in Figure 1(a). But it would be useful to have a mirror that reflects all of the light that falls on it. Analyze the reason for the sparkle of diamonds.Ī good-quality mirror may reflect more than 90% of the light that falls on it, absorbing the rest.Describe the workings and uses of fiber optics.Explain the phenomenon of total internal reflection.
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