As a result, Newton understood that when white light passes through a transparent medium like air into another like glass , its components are deflected the first time according to their colour, and once again when they reemerge back into air, for example. This creates a spread of coloured light rays from red to violet, like the colours of the rainbow.
The spectrum of white light consists of six basic colours arranged in a specific order: red, orange, yellow, green, blue and violet. Although Newton understood that a beam of light of a particular colour is always deviated by the same amount, he did not appear to understand why this is so.
More than a century would pass before another British scientist by the name of Thomas Young would provide part of the answer. Thus, he discovered infrared light. A year later, Johann Wilhelm Ritter was inspired by Herschel's discovery to see if there might be light just beyond the purple end of the spectrum.
Indeed, there was, and Ritter discovered ultraviolet light. In , James Clerk Maxwell predicted that there should be light with even longer wavelengths than infrared light. In Heinrich Hertz demonstrated the existence of the waves predicted by Maxwell by producing radio waves in his laboratory.
It took a bit longer for scientists to discover the higher-energy shorter wavelength light in the electromagnetic spectrum. Right: Mrs. They were first thought to be particles emitted during the course of radioactivity; hence their name, following the identification of alpha particles and beta particles.
William Bragg showed that they ionized gas in , and Ernest Rutherford measured their wavelengths by diffracting them with crystals, demonstrating that they were indeed electromagnetic radiation. Gamma rays are the shortest wavelength, highest frequency, and highest energy form of electromagnetic radiation. All regions of the electromagnetic spectrum are used in spectroscopy.
Figure 5 shows how each region contributes to a form of spectroscopy, many of which have been addressed in previous columns. David W. Ball is a professor of chemistry at Cleveland State University in Ohio. He can be reached at d. The Electromagnetic Spectrum: A History. March 1, Spectroscopy , Spectroscopy, Volume 22, Issue 3. Ball Properties of Light — A Quick Review Light has both particle and wave properties, as has been discussed in a recent column 1. As with any wave, the velocity of light is equal to the product of its frequency and wavelength: Unlike that of other waves, the speed of light is a constant for a given medium.
Figure 1 Because the speed of light is a constant, there is a simple relationship between the wavelength of a light and its frequency. Figure 2 Other Than Visible Light In , British astronomer William Herschel was measuring the effect of various colors of light on a thermometer, using a prism to disperse light from the sun.
Maxwell's Laws The mention of magnets in ancient literature goes back to the 4th century B. The results are The equation has the same form for each quantity. This form is a second-order differential equation whose solution is the classic wave equation: a sine or cosine function which are similarly behaved functions that differ mainly in phase whose velocity is the reciprocal square root of the constants multiplying the second derivative on the right side; that is, The numerical value of this equation is about 3.
The Rest of the Spectrum Figure 3 shows a diagram of the electromagnetic spectrum. Figure 3 Maxwell died in , at age Figure 4 X-rays are a type of ionizing radiation, so-called because X-ray photons have enough energy to eject an electron from an atom, creating ions. Figure 5 David W. Ball, Spectroscopy 21 6 , 30 Then he put a second prism in the way of the green light. If it was the prism that was colouring the light, the green should come out a different colour.
The pure green light remained green, unaffected by the second prism. In another Experiment, after getting a spectrum with his prism, he placed another prism upside-down in the way of the light spectrum after passing the first prism. The band of colors combined again into white sunlight. For a demonstration of this experiment click here.
In these experiments, Newton had proved that white light was made up of colors mixed together, and the prism merely separated them - he was the first person to understand the rainbow. In he performed a famous experiment where he tried to measure the temperature of different colors of the spectrum by placing a thermometer on each colour.
He found to his amazement that the hottest part of the spectrum was in a place where there was no colour at all. It was a spot beyond the red end of the spectrum. For the first time it was possible to talk about invisible light.
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