An area of darkness formed on a surface when an object intercepts the light falling on the surface from a source. In the case of a point source the shadow has a sharply defined outline. If the source has an appreciable size the shadow has two distinct regions; one of full-shadow, called the umbra, the other of half-shadow, called the penumbra.
Shadows.
- ARIN
- Arirang
- ARISE
- Aristarchos Telescope
- Aristarchus of Samos
- Aristarchus of Samos (270 bc)
- Aristarchus of Samos (320–c.250)
- Aristides (5th century bc)
- Aristippus of Cyrene (c.435–350)
- aristocracy
- aristogenesis
- Ariston of Chios (3rd)
- Aristotelianism
- Aristotelian logic
- Aristotle
- Aristotle (384–322)
- Aristotle (384–322 bc)
- Aristotle (384–322 bc)
- Aristotle’s lantern
- Aristotle’s thesis
- arithmetic
- arithmetical hierarchy
- arithmetic and logic unit
- arithmetic function
- arithmetic-geometric mean