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

Refraction and Lenses■ Determine why light raysrefract.■ Explain how convex and concavelenses form images.Many of the images you see everyday in photographs, on TV, and inmovies are made using lenses.Review Vocabularyrefraction: bending of a wave asit changes speed, moving fromone medium to anotherNew Vocabularylens•convex lensconcave lensBending of Light RaysObjects that are in water can sometimes look strange. A pencilin a glass of water sometimes looks as if it’s bent, or as if thepart of the pencil in air is shifted compared to the part in water.A penny that can’t be seen at the bottom of a cup suddenlyappears as you add water to the cup. Illusions such as these aredue to the bending of light rays as they pass from one materialto another. What causes light rays to change direction?The Speeds of Light The speed of light in empty space isabout 300 million m/s. Light passing through a material such asair, water, or glass, however, travels more slowly than this. Thisis because the atoms that make up the material interact with thelight waves and slow them down. Figure 15 compares the speedof light in some different materials.AirThe speed of light through air is about 300 million m/s.WaterFigure 15 Light travels atdifferent speeds in differentmaterials.The speed of light through water is about 227 million m/s.GlassThe speed of light through glass is about 197 million m/s.DiamondThe speed of light through diamond is about 125 million m/s.562 CHAPTER 19 Light, Mirrors, and Lenses