Color

Colors are dependent on light, the primary source of which is sunlight. It is difficult to know what light really is, but we can observe its effects. An object appears colored because of the way it interacts with light. A thin line of light is called a ray; a beam is made up of many rays of light. Light is a form of energy that travels in waves. Light travels silently over long distances at a speed of 190,000 mi (300,000 km) a second. It takes about eight minutes for light to travel from the sun to the earth. This great speed explains why light from shorter distances seems to reach us immediately.

When we talk about light, we usually mean white light. When white light passes through a prism (a triangular transparent object) something very exciting happens. The colors that make up white light disperse into seven bands of color. These bands of color are called a spectrum (from the Latin word for image). When a second prism is placed in just the right position in front of the bands of this spectrum, they merge to form invisible white light again. Isaac Newton (1642-1727) was a well known scientist who conducted research on the sun, light, and color. Through his experiments with prisms, he was the first to demonstrate that white light is composed of the colors of the spectrum.

Seven colors constitute white light: red, orange, yellow, green, blue, indigo, and violet. Students in school often memorize acronyms like ROY G BIV, to remember the seven colors of the spectrum and their order. Sometimes blue and indigo are treated as one color. In any spectrum the bands of color are always organized in this order from left to right. There are also wavelengths outside the visible spectrum, such as ultraviolet.