Optically smooth

{
  "id": "MLC-T-MET-007719",
  "term": "Optically smooth",
  "field": "Meteorology and atmospheric science",
  "definition": "Describing a surface that appears perfectly flat and free of irregularities when viewed with light, meaning its roughness is significantly smaller than the wavelength of the incident light. For visible light, this generally implies surface variations on the order of tens of nanometers or less. Such surfaces reflect light specularly rather than diffusely.",
  "url": "https://mlchart.com/terminology/meteorology/optically-smooth/"
}