| SUNDOG | Bright spot on a solar halo caused by diffraction of light by ice crystals in the atmosphere; a parhelion (6) |
| HALO | Bright circle around the sun or moon caused by the refraction or reflection of light by ice crystals in the atmosphere (4) |
| CORONA | Aureola of the sun or moon caused by diffraction by cloud droplets or ice crystals; the trumpet of a daffodil or other narcissus; or, a circular chandelier in a church (6) |
| SUNSPOT | Relatively cool area on a solar surface |
| MOONDOG | Bright spot on a meteorological halo |
| BLIP | Bright spot on a radar screen |
| BEZEL | A grooved ring holding a lens, precious stone or watch crystal in its setting; a chamfer; one of the oblique facets of a cut gem; or, an indicator light on a car dashboard (5) |
| VAPOURTRAILS | Streams of ice crystals in the wake of aircraft (6,6) |
| FRINGE | A border of loose threads, tassels or twists; hair or "bangs" falling over one's brow; non-mainstream theatre; or, a bright or dark band produced by diffraction or interference of light (6) |
| LAUE | Max von -; physicist awarded a Nobel Prize for his discovery of the diffraction of X-rays by crystals (4) |
| THOMSON | J. J. -; discoverer of the electron whose son George co-discovered the diffraction of electrons by crystals (7) |
| UMBRA | Region of complete shadow resulting from the total obstruction of light by an opaque object, as in a solar eclipse |
| SPINEL | A mineral or gem such as the Black Prince's ruby or the stone of one who is August born, named for its crystals in octahedral form, like a "thorn" (6) |
| SPECTRUM | The distribution of colours produced when white light is dispersed by a prism or diffraction grating (8) |
| PARHELION | Atmospheric ice-crystal halo and glorious light show whose etymology perfectly reflects the phenomenon's appearance: a bright spot appearing beside the Sun, hence "mock sun" (9) |
| AIRY | Light I observed in diffraction of ray (4) |
| PLAGE | Bright spot on the sun |
| FACULA | Bright spot on the sun |
| OPAL | So hydrated/watery it could almost fall like mermaids' tears, a mineral whose prismatic play of colour is caused by light diffraction through silica spheres (4) |
| MIKEWAZOWSKI | One-eyed monster voiced by Billy Crystal in the 'Monsters Inc.' film franchise (4,8) |
