Light Study Guide
Pages 176 - 195
Lightis a form of energy that you can see. Light, like sound, travels in waves. Light waves travel in straightlines in all directionsawayfrom their source. Light waves can travel through empty spaceand that is how light from the sunreaches Earth and other planets.
Without light we cannot see. Most objects do not give out their own light, but we can still see them because they reflectlight from something else into our eyes. Light waves reflect, or bounce off, the surfaces of most objects. For example, when you see the moonbecause it reflects light from the sun to your eyes. When you look in a mirror, light waves reflectback to your eyes because the mirror’s surface is smoothand shiny. You can see a clear reflection of yourself in the mirror. When light waves reflect off of roughsurfaces, they bounce off in many different directions, and that is why you see the object itself, not your reflection.
Some materials allow lightto pass straight through them. These materials, such as a window glass or clear plastic, are called transparent. You can see a clear image through transparentmaterial. Translucentmaterials let some light pass through them, but the light scatters in many directions. When you look through translucentmaterials, objects will look blurry. Some examples of translucentmaterials are frosted glass and wax paper. An opaquematerial lets no light pass through, so you will see no image when you look through an opaquematerial. Some examples of opaquematerials are wood, metal, and rocks.
Lenses and Light
Refractmeans to bend. All transparent materials, such as clear glass and plastic and water, can bend light. A lensis a piece of curved glass, plastic, or other materials that refractslight. There are two main types of lenses: convexand concave.
A convexlens is thicker in the middle than it is around the edges. Convexlenses make things look bigger when you look through them. Convexlenses are very useful because of their ability to magnify objects. Some examples of where convexlenses are used are eyeglasses (for people who are farsighted), telescopes, microscopes, binoculars, and magnifying glasses.
A concavelens is thinner in the middle than it is around the edges. Concavelenses make things look smaller. Some examples of where concavelenses are used are eyeglasses (for people who are nearsighted), binoculars, and movie projectors.
Prisms and Light
Sunlight is also called whitelight. Whitelight is made up of light waves of different colors. You can separatewhite light into bands of color using a prism. A prismis a transparent object that separateswhite light into all the colors of the rainbow. The colors of a rainbow make up the visiblespectrum (the range of light energy that people can see). Have you ever seen a rainbow? Rainbows form because raindrops act as tiny prismsto breakup sunlight into the visiblespectrum. Although there are many colors in a rainbow, most people use seven colors to describe them: red, orange, yellow, green, blue, indigo, and violet(ROY G BIV).