Elaine Casciano, age 11, of Allentown, Pa., for her question:
WHAT IS LIGHT?
Daylight comes from the sun, the star around which the planets in our solar system revolve. It is 93 million miles from the earth and gives off so much light hat it uses up fuel at the rate of 60 million tons of its weight every minute. We see the planets in the night sky because they reflect sunlight to our eyes just as we see an apple on a table across the room at night by the light it reflects to our eyes from a lamp in the room.
Light, very simply, is something that makes things visible or affords illumination.
Materials which are heated to above 1,400 degrees Fahrenheit produce light. This is how we explain sunlight, and also light from an electric bulb's filament.
Energy seen as light is generally from another energy sour e, such as the electrical or heat energy which excites atoms. The atoms take in this energy, causing their electrons to shift to higher orbital energy levels. When the electrons snap back to their lower or original orbits, energy is again released in a new form, that of light (radiation), which can be sensed by the eyes.
Yes, you are right. Explaining light is most difficult.
Light travels in straight lines ordinarily and at great speed. We can see from looking at a flashlight's beam that the path of light is straight. We give the name "light ray'' to each little straight line that connects the source of the light the light bulb with the object it lights up. We think of a beam of light as being made up of a bundle of light rays.
Light can be reflected and absorbed by objects, and it can also be bent. This happens when a light beam strikes a smooth sheet of glass that is standing at an angle. The side of the beam nearest the glass slows down first, so the beam is turned. When the beam comes out the other side of the glass it turns back to its original direction. This bending of a beam of light as it passes from one transparent material to another is called refraction.
Light is measured by a photoelectric meter. Light energy striking the surface of specially treated substances will cause a flow of electrons which will be circuited through a piece of equipment called a galvanometer. The units for measuring light intensity are called lumens or foot candles. Light can be converted directly to electrical energy, by the way, in solar cells.
Life is dependent upon light. Our world couldn't function without it.
Without the trapping and storing of light energy in living plants, there would be no chain of life. All life depends on this vitally important process which we call photosynthesis.