| RefNo | MS/242/1 |
| Level | Item |
| Title | Letter from Jean François Dominique Arago to Thomas Young, dated at the Observatoire Royal, Paris |
| Date | 13 July 1816 |
| Description | Letter addressed to Young, as Secretary of the Royal Society.
Forwards a treatise on the diffraction of light by [Augustin Jean] Fresnel, which was recently published in the Annales de Chimie et de Physique edited by Arago and [Joseph Louis] Gay-Lussac. Fresnel was unaware of Young's writings published in Phil. Trans. on the topic when he first wrote on the matter. Arago has shared the articles with Fresnel, who now recognises Young's priority and the importance of his researches.
Fresnel's essay demonstrates Young's doctrine of interference. Those who support the idea that light is emitted will not be able to explain the curved trajectory of the diffracted band of light. Although Arago suspects that rather than admitting that their hypothesis is incorrect, they will just stay silent on the matter.
[Jean-Baptiste] Biot's voluminous Traité de physique experimentale et mathematique already circulates in England, Young will have therefore seen Biot's pitiful attempt to prove that two rays of light crossing do not interact at all, against Young. Arago will soon devote some time to the matter, in the meantime he has included two notes in the Annales to make the public aware of the matter and of Young's ingenious work. One relates to the experiment of the disappearance of internal bands of light, published in Phil. Trans. 1803, to which Arago has added an important correlation: the disappearance of the full band of diffracted light when under an opaque shadow also happens when the opaque screen is switched for a diaphaneous glass, this is useful to measure very precisely the smallest difference in refraction. Arago is planning to recreate the experiment soon, which he hopes will be successful also with gaseous substances.
The letter will be delivered by [Charles] Dupin, a very distinguished [naval] engineer, highly recommended by [Alexander van] Humboldt.
Signature has been cut-out from last page. |
| Language | French |
| Extent | 3p |
| Format | Manuscript |
| PhysicalDescription | Paper |
| AccessStatus | Open |
Fellows associated with this archive
| Code | PersonName | Dates |
| NA7947 | Young; Thomas (1773 - 1829); physician, physicist and Egyptologist | 1773 - 1829 |
| NA2974 | Arago; Dominique Francois Jean (1786 - 1853); mathematician, physicist, astronomer and politician | 1786 - 1853 |