The Nature Of Light And The Principle Of Ray Optics



The Nature Of Light And The Principle Of Ray Optics

The Concept From Physics

Most scientists accepted Newton's particle theory. During his lifetime, however, another theory was proposed—one that argued that light might be some sort of wave motion. In 1678, the Dutch physicist and astronomer Christian Huygens showed that a wave theory of light could also explain re?ection and refraction. In 1801, Thomas Young (1773-1829) provided the ?rst clear demonstration of the wave nature of light. Young showed that, under appropriate conditions, light rays interfere with each other. Such behavior could not be explained at that time by a particle theory because there was no conceivable way in which two or more particles could come together and cancel one another. Additional developments during the nineteenth century led to the general acceptance of the wave theory of light, the most important resulting from the work of Maxwell, who in 1873 asserted that light was a form of high-frequency electromagnetic wave. As discussed in Chapter 34, Hertz provided experimental con?rmation of Maxwell's theory in 1887 by producing and detecting electromagnetic waves(Hecht, 2010).

Practical Example Of Physics At Work

Light travels at such a high speed (c ! 3.00 " 10 8 m/s) that early attempts to measure its speed were unsuccessful. Galileo attempted to measure the speed of light by positioning two observers in towers separated by approximately 10 km. Each observer carried a shuttered lantern. One observer would open his lantern ?rst, and then the other would open his lantern at the moment he saw the light from the ?rst lantern. Galileo reasoned that, knowing the transit time of the light beams from one lantern to the other, he could obtain the speed. His results were inconclusive. Today, we realize (as Galileo concluded) that it ...