Historical figure · Pearson Edexcel International GCSE revision on Incandio

John Tyndall

Who Bent Light Round A Corner · Physicist & Mountaineer · 1820–1893

Faraday's successor at the Royal Institution, who showed six hundred people that light will follow a curving stream of falling water rather than go straight on — and who found why the Earth is warm.

Defend these ideas against Tyndall

Incandio is a free revision platform for the Pearson Edexcel International GCSE, and on it a topic counts as mastered only once you have learned it, proved it in questions, taught it back and defended it against the person with the strongest claim on it. John Tyndall is that person for one topic on the course:

• Total Internal Reflection — Physics

Who was Tyndall?

John Tyndall was born in County Carlow in 1820, worked as a railway surveyor and a schoolmaster, and got his physics at Marburg under Bunsen and Knoblauch before joining the Royal Institution in London, where he succeeded Michael Faraday and became the most admired scientific lecturer of the age. In 1854 he gave a demonstration that has outlived nearly everything else he did: a vessel of water lit from behind, with a hole in its side, so that the water arcs out and falls — and the light travels down the arc with it instead of continuing straight on, because at every point it meets the inside surface of the stream at too great a slant to get out, and is thrown back in again and again all the way down. Colladon had shown it in Geneva in 1842 and Babinet earlier, a priority Tyndall did not always make plain. His own most important research is on the absorption of radiant heat by gases: he found that the main constituents of the air, oxygen and nitrogen, are almost transparent to it, while water vapour and carbon dioxide absorb it strongly — which is why the Earth retains its heat, and the first experimental basis for what is now called the greenhouse effect. He explained the blue of the sky by the scattering of light by fine particles, making a blue sky and a red sunset in a tube on the lecture bench, and his work on dust-free air supported Pasteur against spontaneous generation. He was a serious alpinist and among the first to climb the Weisshorn.

Major achievements

• Demonstrated in 1854 that light can be guided along a curved stream of water by total internal reflection
• Discovered that water vapour and carbon dioxide absorb radiant heat while oxygen and nitrogen do not
• Explained the blue of the sky and the red of sunset by scattering, and reproduced both on a bench
• Showed that dust-free air does not generate life, supporting Pasteur's germ theory
• Studied glacier motion and regelation

Life in brief

• 1820 — Born in County Carlow: A constable's son; railway surveying first.
• 1848 — Marburg: Physics under Bunsen and Knoblauch.
• 1853 — Royal Institution: Professor, alongside Faraday.
• 1854 — The lit water jet: Light guided round a curve, in front of an audience.
• 1859 — Radiant heat and the gases: Water vapour and carbonic acid trap the Earth's heat.
• 1861 — The Weisshorn: Among the first to the summit.
• 1893 — Dies at Hindhead: An accidental overdose of chloral.

Explore the life of Tyndall — five chapters

1. From a Railway Cutting to the Royal Institution — A constable's son, and physics learned in Germany
2. Light Round a Bend — 1854, and the principle of the optical fibre
3. Which Gases Trap the Heat — 1859, and the first measurements of the greenhouse effect
4. A Blue Sky in a Glass Tube — Scattering, dust-free air, and Pasteur
5. The Belfast Address — A public quarrel, and an accidental death

Read the five-chapter life of John Tyndall →

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