Rule 1: After reflection, a ray of light parallel to the principal axis appears to be coming from focus. Rule 2: A ray of light going towards centre of curvature is reflected back along the same path.

During the first light observations, several test targets were observed using the many different modes of SPHERE. These include one of the best images so far of the ring of dust around the nearby ...

Light can be reflected not only in space but also in time—and researchers exploring such “time reflections” are finding a wealth of delightfully odd and useful effects ...

Tohoku University. "Probing semiconductor crystals with a sphere of light." ScienceDaily. ScienceDaily, 8 June 2019. <www.sciencedaily.com / releases / 2019 / 06 / 190607110452.htm>.