11 June

1867: On 11 June 1867, Charles Fabry was born.

Fabry was a French physicist who specialised in optics, devising methods for the accurate interferometry. He worked with Alfred Pérot, during 1896-1906, on the design and uses of a device known as the Fabry-Pérot interferometer, specifically for high-resolution spectroscopy, composed of two thinly silvered glass plates placed in parallel, producing interference due to multiple reflections.

In 1913, Fabry demonstrated that ozone is plentiful in the upper atmosphere and is responsible for filtering out ultraviolet radiation from the Sun, protecting life on the surface of Earth from most of its harmful effects.

1292: On 11 June 1292, Roger Bacon died.

He was an English scholar who was one of the first to propose mathematics and experimentation as appropriate methods of science. He studied mathematics, astronomy, optics, alchemy, and languages. He developed the principles of refraction, reflection, and spherical aberration, and described spectacles, which soon thereafter came into use. He used a camera obscura to observe eclipses of the Sun.