In the seventeenth century, Sir Isaac Newton discovered that the light of the Sun could separated into a rainbow of colors using a special piece of glass called a prism (see the illustration above). This rainbow of colors is called a spectrum. Newton's experiment showed that even though the Sun appears yellowish-white when you look at it (but don't do that often!), the light of the Sun contains all colors of light, from red to blue.
In 1802, William Wollaston made another startling discovery. The spectrum of the Sun was not a solid band of color (known as a continuous spectrum), there were small, black gaps, or lines, in it! These small gaps became known as an absorption line spectrum. It was later discovered that the corona of the Sun (which is an outer layer only seen during an eclipse) had a spectrum with no bands of color. Instead, it had a black spectrum with narrow, bright lines of color. This type of spectrum became known as an emission line spectrum.
In the middle of the nineteenth century, it became apparent to scientists that each element had its own pattern of spectrum lines. These spectrum lines could be used, like a fingerprint, to identify elements. But, still noone knew how the spectrum lines were created. In 1859, Gustav Kirchhoff finally explained the basic rules for the creation of spectrum lines. However, scientists would have to delve into the realm of the atom before truly understaning how spectrum lines are formed.
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