Newton found that sunlight, which looks white to us, is actually made up of a mixture of all the colors of the rainbow ( Figure 5.9).įigure 5.9 Action of a Prism. In 1672, in the first paper that he submitted to the Royal Society, Sir Isaac Newton described an experiment in which he permitted sunlight to pass through a small hole and then through a prism. For now, we turn to another behavior of light, one that is essential for the decoding of light. We will discuss astronomical instruments and their uses more fully in Astronomical Instruments. Small optical devices, such as eyeglasses or binoculars, generally use lenses, whereas large telescopes depend almost entirely on mirrors for their main optical elements. Such instruments are generally combinations of glass lenses, which bend light according to the principles of refraction, and curved mirrors, which depend on the properties of reflection. Reflection and refraction of light are the basic properties that make possible all optical instruments (devices that help us to see things better)-from eyeglasses to giant astronomical telescopes. Light is also bent, or refracted, when it passes from one kind of transparent material into another-say, from the air into a glass lens. If the surface is smooth and shiny, as with a mirror, the direction of the reflected light beam can be calculated accurately from knowledge of the shape of the reflecting surface. For example, light can be reflected from a surface. Light exhibits certain behaviors that are important to the design of telescopes and other instruments. Let’s examine how we can do this and what we can learn. To extract this information, however, astronomers must be able to study the amounts of energy we receive at different wavelengths of light in fine detail. Explain how astronomers learn the composition of a gas by examining its spectral linesĮlectromagnetic radiation carries a lot of information about the nature of stars and other astronomical objects.By the end of this section, you will be able to:
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