Light Mirrors and Lenses (3379.0K) - McGraw-Hill Higher Education

Properties of Light■ Describe the wave nature oflight.■ Explain how light interacts withmaterials.■ Determine why objects appearto have color.Everything you see comes frominformation carried by light waves.Review Vocabularyelectromagnetic waves: wavescreated by vibrating electriccharges that can travel throughspace or through matterNew Vocabularylight ray• mediumWhat is light?Drop a rock on the smooth surface of a pond and you’ll seeripples spread outward from the spot where the rock struck. Therock produced a wave much like the one in Figure 1. A wave isa disturbance that carries energy through matter or space. Thematter in this case is the water, and the energy originally comesfrom the impact of the rock. As the ripples spread out, they carrysome of that energy.Light is another type of wave that carries energy. A source oflight such as the Sun or a lightbulb gives off light waves intospace, just as the rock hitting the pond causes waves to form inthe water. But while the water waves spread out only on the surfaceof the pond, light waves spread out in all directions fromthe light source. Figure 1 shows how light waves travel.Sometimes, however, it is easier to think of light in a differentway. A light ray is a narrow beam of light that travels in astraight line. You can think of a source of light as giving off, oremitting, a countless number of light rays that are travelingaway from the source in all directions.Figure 1 Light movesaway in all directionsfrom a light source,just as ripples spreadout on the surfaceof water.A source of light, such as a lightbulb,gives off light rays that travel awayfrom the light source in all directions.Ripples on the surface of a pond are produced by anobject hitting the water. The ripples spread outfrom the point of impact.550 CHAPTER 19 Light, Mirrors, and LensesDick Thomas/Visuals Unlimited