| Answer | Crossword Clue |
|---|---|
| echelle | a diffraction grating made by ruling a plane metallic mirror with lines having a relatively wide spacing |
| Answer | Crossword Clue |
|---|---|
| echelle | a diffraction grating made by ruling a plane metallic mirror with lines having a relatively wide spacing |
Crossword
a puzzle consisting of a grid of squares and blanks into which words crossing vertically and horizontally are written according to clues.