Spectral lines

1814 Spectral lines

The book of science

Tom Sharp

Joseph von Fraunhofer physics Spectral lines

Spectral lines

In the gaseous atmosphere of the sun each element absorbed a different combination of wavelengths leaving its own pattern of dark lines visible in the spectroscope that Joseph von Fraunhofer in Bavaria built using his famous achromatic lenses. Peering through a small scope mounted to calibrate a circular scale von Fraunhofer counted 574 and measured the wavelengths of 324 spectral lines. A pure scientific observation began a sequence of inspirations resulting in a practical tool for chemical and astronomical analysis.


Isaac Newton didn’t get it. William Hyde didn’t get it. But after Joseph von Fraunhofer everyone got it. Robert Bunsen got it. Gustav Kirchhoff got it. William Huggins got it. That each element has its own absorption pattern, that the chemical composition of laboratory samples can be identified by their spectral lines, that helium, caesium, rubidium, neon, and argon exist, and that the sun, the stars, and the nebulae are composed of the same elements as the earth.

Spectral analysis

The humanist believes each human being is unique including human beings like me —like each snowflake —each piece of popcorn. But convert those flakes or kernels to a gas and get their spectral signatures— anyone can see they’re all the same.

Joseph von Fraunhofer was an orphan apprentised to a glassmaker. His workhouse collapsed and he was buried in the rubble, but he was rescued by Prince Maximilian Joseph, who subsequently ensured that Joseph was treated better and could continue his education.

Early opticians ground their own lenses; von Fraunhofer constructed his own furnace, invented and made his own glass, designed and built machines for grinding and polishing lenses, and designed his own optical instruments. He designed and built telescopes and microscopes, and he invented the spectroscope.

Like the other glassmakers of his time, he was poisoned by heavy metal vapors and died young.

The absorption lines in the solar spectrum are still named Fraunhafer lines.

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